Dermatologic Clinics
Volume 23 • Number 2 • April 2005
Copyright © 2005 W. B. Saunders Company









The Use of Systemic Immune Moderators in Dermatology: An Update


Dana Kazlow Stern, MD a
Jackie M. Tripp, MD b
Vincent C. Ho, MD b
Mark Lebwohl, MD c, *



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a Department of Dermatology, Mount Sinai Medical Center, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, Box 1048, New York, NY 10029-6574, USA
b Division of Dermatology, Department of Medicine, Vancouver Hospital and Health Sciences Center and University of British Columbia, 835 West 10th Avenue, Vancouver, BC V5Z 4E8, Canada
c Department of Dermatology, The Mount Sinai School of Medicine, Mount Sinai Medical Center, Clinical Trials Center, 5 East 98th Street, 5th floor, New York, NY 10029-6574, USA
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* Corresponding author

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E-mail address: mark.lebwohl@mssm.edu



Dr. Stern has been an investigator for Biogen Idec, Inc., Genentech, Inc., Amgen, Inc., and Centocor Inc. Dr. Lebwohl has been an investigator, speaker, and consultant for Centocor, Inc., Biogen Idec, Inc., Genentech, Inc., and Amgen Inc., and he has been a speaker and investigator for Abbott, Inc.
PII S0733-8635(04)00092-0


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In addition to corticosteroids, dermatologists have access to an array of immunomodulatory therapies. Azathioprine, cyclophosphamide, methotrexate, cyclosporine, and mycophenolate mofetil are the systemic immunosuppressive agents most commonly used by dermatologists. In addition, new developments in biotechnology have spurred the development of immunobiologic agents that are able to target the immunologic process of many inflammatory disorders at specific points along the inflammatory cascade. Alefacept, efalizumab, etanercept, and infliximab are the immunobiologic agents that are currently the most well known and most commonly used by dermatologists. This article reviews the pharmacology, mechanism of action, side effects, and clinical applications of these therapies.


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When inflammatory dermatoses are severe or recalcitrant to topical therapies, dermatologists are occasionally required to prescribe immunomodulatory drugs. The first-line systemic anti-inflammatory therapy is the oral administration of corticosteroids, but frequently other immunomodulatory drugs are needed to control disease activity, while at the same time limiting or even eliminating the need for corticosteroids. These immunomodulatory therapies can be divided into two broad categories: the more traditional and well-known nonsteroidal immune-modifying drugs, also commonly referred to as the systemic therapies, and the newer immunobiologic agents.

The most common nonsteroidal immune-modifying drugs include the following agents: azathioprine, cyclophosphamide, cyclosporine, methotrexate, and mycophenolate mofetil (MMF). These agents are predominantly cytotoxic, but data seem to suggest that methotrexate has significant anti-inflammatory activity as well. The other category encompasses the plethora of newer immunobiologic agents that are being developed, the most well known of which include alefacept, efalizumab, etanercept, and infliximab. The current authors and others have previously reviewed the pharmacology, mode of action, and adverse effects of some of these agents [1], [2], [3], [4], [5], [6]. The current article reviews new data concerning the pharmacology, mechanism of action, adverse effects, and dermatologic applications of these two categories of therapeutic agent. Familiarity with the disease-specific clinical efficacy of each of these medications and their dosages and side-effect profiles allows for the proper and efficacious use of these drugs to treat dermatologic disease.



AZATHIOPRINE
Inititially used as an immunosuppressant for renal transplantation, azathioprine has been available for more than 40 years, and because of its relatively favorable therapeutic index, it is one of the more commonly used immunomodulatory drugs in dermatology. Structurally, it is a synthetic purine analog formed by attaching an imidazole ring to 6-mercaptopurine (6-MP). This analog is a prodrug and is quickly converted to 6-MP by a nonenzymatic nucleophilic attack by sulfhydryl compounds present in erythrocytes and body tissues.



PHARMACOLOGY
A comparison of the main pharmacologic attributes of the immunosuppressants discussed in this article is presented in Table 1. Azathioprine is rapidly absorbed after oral administration. The drug has a plasma half-life of only 3 hours because of its conversion to 6-MP. Active metabolites have a long half-life, however, allowing once-daily dosing. The 6-MP is metabolized by means of three competing pathways: thiopurine methyltransferase (TPMT) catalyzes S-methylation to 6-methyl mercaptopurine, an inactive compound. Xanthine oxidase catalyzes oxidation to the inactive 6-thiouric acid. Hypoxanthine-guanine phosphoribosyl transferase (HGPRT) catalyzes the conversion of 6-MP to the active 6-thioguanine metabolites. Erythrocyte levels of 6-thioguanine nucleotides correlate with absolute neutrophil counts [7], and steady-state levels may take days to years to achieve. A genetic polymorphism controls TPMT activity. In a recent review of more than 3000 patients, approximately 80% of the patients had normal TPMT activity, 9% had enzymatic activity that was above normal, and 10% displayed low activity [8]. It was also found that 0.45% (1:220) of the study population had no detectable enzyme activity. This ratio is higher than the previously reported 1 in 300 occurrence of undetectable TPMT levels in the population reported in other smaller studies. In renal transplant patients, low TPMT activity has been found to correlate with a higher incidence of leukopenia caused by azathioprine, and those with higher levels were found to be less immunosuppressed [9]. Patients with intermediate TPMT activity may be more likely to develop late-onset neutropenia [10].


Table 1 . Pharmacology of the common immunosuppressants used in dermatology Features Azathioprine Cyclophosphamide Methotrexate Cyclosporine MMF
Mechanism of action Cell cycle–specific antimetabolite, inhibition of neutrophil trafficking, inhibition of cellular cytotoxicity Non–cell cycle–specific antimetabolite, selective macrophage inhibition, selective B-cell suppression Cell cycle–specific antimetabolite, inhibition of neutrophil chemotaxis, inhibition of IL-1, IL-6, and IL-8 release Inhibition of signal transduction and IL-2 production in lymphocytes Cell cycle–specific antimetabolite, inhibition of Tc and B-cell proliferation
Rate of onset of clinical immunosuppression Slow (4–8 wk) Moderately rapid (2–4 wk) Moderately rapid (2–4 wk) Rapid (1–2 wk) Slow (4–8 wk)
Route of administration Per os Per os/IV Per os/SC/intramuscular/IV Per os Per os
Route of elimination Hepatic metabolism and renal excretion Hepatic metabolism and renal excretion Renal excretion by active tubular secretion Hepatic metabolism Hepatic metabolism and renal excretion
Dose modification in presence of:
Renal insufficiency Moderate decrease in dosage may be required Moderate decrease in dosage may be required Relatively contraindicated, significant dose reduction necessary No change in dosage necessary Moderate decrease in dosage may be required
Hepatic insufficiency No change in dose necessary Moderate decrease in dosage may be required Moderate decrease in dosage may be required Significant dose alteration needed No change in dose necessary
Major potential drug interactions Allopurinol, warfarin Allopurinol Probenecid, NSAIDs, cotrimazole Multiple (see text) Acyclovir, iron, antacids, cholestyramine
Major toxicity Bone marrow depression, carcinogenesis Bone marrow depression, hemorrhagic cystitis, carcinogenesis Hepatotoxicity, bone marrow depression, carcinogenesis Hypertension, nephrotoxicity, carcinogenesis Bone marrow depression, carcinogenesis

The determination of pretreatment red blood cell TPMT activity has been advocated to detect those patients at risk for early-onset neutropenia [11]. This test can be accomplished using either a radiochemical assay of enzyme activity or by high-pressure liquid chromotography. Recently, the isolation and characterization of mutant alleles causing TPMT deficiency have enabled identification of more than 80% of all TPMT mutant alleles in white persons and have allowed the diagnosis of TPMT deficiency and heterozygosity based on genotype [12]. If the drug is used without pretreatment measurement of TPMT activity, it is now recommended that patients be counseled about the associated risks and the inadequacy of blood count monitoring as a method of preventing early toxicity [13]. TPMT measurement is becoming more widely available, and one recent cost-effectiveness study has shown that polymerase chain reaction testing to identify TPMT polymorphisms before treatment represents good economic value in certain health care settings [14].

Other factors affect TPMT activity. Sulfasalazine and its metabolite 5-aminosalicylic acid inhibit TPMT activity, whereas 6-MP itself and diuretics can induce its activity [15]. Further, very low lymphocyte activities of 5-nucleotidase have been documented in transplant recipients with normal TPMT activity who developed neutropenia when given azathioprine. All patients require tailoring of this medication, guided by leukocyte and platelet counts.

The 6-thioguanine metabolites prevent the interconversion of purine bases and inhibit de novo biosynthesis of purine bases in an S-phase–specific fashion. This antiproliferative effect may not be solely responsible for the immunosuppressive action of azathioprine, because effects on natural killer cell (NKC) function, T-cell signaling, T-cell cytolytic activity, prostaglandin production, and neutrophil activity have been noted [1]. No significant changes in interleukin (IL) levels have been noted.



ADVERSE EFFECTS


HEMATOLOGIC
Myelosuppression, manifesting as leukopenia, thrombocytopenia, or pancytopenia, is the most significant adverse effect of azathioprine. As stated previously, early toxicity, which is of rapid onset and severe, may be predicted by a knowledge of TPMT activity. Continued monitoring is required, because late-onset myelosuppression occurs more slowly and may be delayed for years. Significant leukopenia was seen in 10% of patients (3 of 29) who had pemphigus vulgaris treated at a mean dosage of 2 mg/kg per day for 4 to 12 years [16], and, in a survey of azathioprine use by dermatologists in the United Kingdom, 45% of respondents had observed significant myelosuppression [17].



GASTROINTESTINAL
Nausea and vomiting are the most frequent side effects, occurring 12.4 times and 5.1 times per 100 patient-years, respectively, in patients receiving standard dosages for rheumatoid arthritis (RA), an average of 104 mg per day [18]. A recent study has shown that azathioprine-related gastrointestinal side effects are independent of TPMT polymorphism [19]. Hepatotoxicity was noted in 8% of patients receiving azathioprine and prednisolone for bullous pemphigoid [20].



OPPORTUNISTIC INFECTIONS
An increased susceptibility to opportunistic infections has been reported in patients receiving both azathioprine and corticosteroids, even in the absence of leukopenia. Eruptions of herpes simplex, herpes zoster, and verrucae may be more common [1].



ONCOGENIC POTENTIAL
Azathioprine has been associated with an increased incidence of malignancy in renal transplant patients. Malignancies have included lymphomas, Kaposi's sarcoma, renal carcinomas, carcinomas of the cervix and vulva, and skin cancers [21]. An analysis of the risk of skin cancer in renal transplant recipients, with a multivariate analysis of subgroups on either long-term cyclosporine or azathioprine with or without corticosteroids, showed no differences between the groups, suggesting that the increased risk is associated with the drug-induced immunosuppression and is independent of the agents used to achieve this [22]. An analysis of 1191 patients who have multiple sclerosis (MS) identified patients who have cancer, matched them to patients who do not have cancer, and compared them in terms of exposure to azathioprine therapy [23]. MS patients given azathioprine were found to have a relative increase in cancer risk of 1.3 when treated less than 5 years, of 2.0 when treated 5 to 10 years, and of 4.4 when treated more than 10 years. Wide confidence intervals undermined these results, but overall, the long-term risk for these patients was low. A more recent retrospective study of 626 patients taking azathioprine who were observed for a mean duration of 6.9 years showed no increased risk of cancer diagnosis [24].



HYPERSENSITIVITY REACTIONS
Several reports call attention to azathioprine hypersensitivity syndrome [25], [26], [27], [28]. This syndrome has been reviewed comprehensively by Saway et al [29]. The time of onset is from 3 hours to 42 days after onset of medication use, with a mean of 14 days. Hypersensitivity syndrome is rare, with some 30 case reports in the literature. Manifestations may include the following: hypotension; shock; a maculopapular, urticarial, or vasculitic eruption; fever; acute hepatotoxicity; pancreatitis; rhabdomyolysis; acute renal failure; and pneumonitis. Recently, a higher incidence of acute febrile toxic reaction has been reported in 4 of 43 patients (9.3%) with RA who were on long-term methotrexate and in whom azathioprine in usual dosages was added, suggesting a possible adverse drug interaction [30].



MISCELLANEOUS
Azathioprine, used in conjunction with isotretinoin, has been reported to induce curling of hair [31]. Azathioprine and isotretinoin also have been associated independently with the development of curly hair. In addition, azathioprine administered following corneal transplantation has been reported to cause bilateral macular hemorrhage secondary to aplastic anemia [32].



CLINICAL USE IN DERMATOLOGY
A 1997 survey of current practice in the use of azathioprine by dermatologists in the United Kingdom revealed that the most common indications for its use were the immunobullous disorders (pemphigoid and pemphigus, where it was used in conjunction with corticosteroids), atopic dermatitis and chronic actinic dermatitis (both more often in the absence of corticosteroids), and dermatomyositis (again as a steroid-sparing agent) [17]. Other common uses included pyoderma gangrenosum, systemic lupus erythematosus, psoriasis, lichen planus, and cutaneous lupus erythematosus. There remain very few controlled trials to support the drug's use in dermatology. The data supporting the adjuvant use of azathioprine in pemphigus were reviewed; these data consisted of seven studies totalling 105 patients with no significant difference in outcome between patients treated with cyclophosphamide or azathioprine [33]. Likewise, the use of azathioprine in pemphigoid has been variably shown to have a steroid-sparing effect [1], and in a study in which dosages of both corticosteroid and azathioprine were fixed [20], to result in more adverse effects. Azathioprine may be effective as a steroid-sparing agent in moderately severe systemic lupus, but there is conflicting evidence as to its efficacy in severe disease [1]. The efficacy of azathioprine in dermatomyositis-polymyositis also has been questioned [34].

A retrospective review of 35 patients who had severe, longstanding atopic dermatitis treated with azathioprine showed that 3 of 35 patients had severe nausea, which resulted in treatment discontinuation. The median difference in disability index before and after treatment was highly significant in the 32 patients who tolerated the drug [35]. More recently, a double-blind, randomized, placebo-controlled trial of azathioprine was performed in 37 adult patients who had severe atopic dermatitis (AD), and it similarly showed significant improvement in symptom scores. There were, however, gastrointestinal side effects in 14 patients [36]. A favorable short-term response to azathioprine in four patients with intractable prurigo nodularis also has been reported [37].

The efficacy of azathioprine in controlling the ocular and extraocular manifestations of Behçet's disease was shown in a double-blind controlled trial [38]. The follow-up of this study showed that the beneficial effect of treatment favorably affected the long-term prognosis of these patients [39].

Azathioprine has been shown to be an effective steroid-sparing agent for generalized lichen planus [40] and also has been used successfully as monotherapy in two patients [41].



USAGE GUIDELINES
Azathioprine is contraindicated in patients with known hypersensitivity to the drug. Dosage adjustment, as guided by serial blood counts, may be required in patients with hepatic or renal insufficiency. The drug should not be used during pregnancy unless the benefits outweigh the risks. Both the parent drug and its metabolites can cross the placenta and act as potential teratogens. The magnitude of the teratogenic risk has been evaluated as minimal to small [42], [43]. In contrast to the other cytotoxic agents, there is no evidence that azathioprine produces gonadotoxicity or infertility.



DRUG INTERACTIONS
Because allopurinol inhibits the metabolism of azathioprine by xanthine oxidase, the two drugs should not be used concurrently if possible. During concurrent therapy, the dosage of azathioprine should be decreased by at least two thirds, although this dosage reduces, but does not abolish, the risk of myelotoxicity [44]. In this clinical situation, the monitoring of 6-thioguanine levels would seem warranted [45].

Angiotensin-converting enzyme (ACE) inhibitors have been shown to potentiate anemia in renal transplant patients concurrently on azathioprine [46]. This finding seems to be caused by the erythropoietin-lowering effect of the ACE inhibitors rather than from a pharmacokinetic interaction between the two drugs [47]. To the current authors' knowledge, a clinically significant interaction has not been documented in a nonrenal transplant setting, although the current American College of Rheumatology guidelines advise against this combination [48]. Both azathioprine and trimethoprim-sulfamethoxazole are antimetabolites that have a synergistic effect in inhibiting bone marrow proliferation [49]. Again, however, no significant interaction was noted in renal transplant patients treated with concomitant therapy over 4 months [50]. Because of inhibition of TPMT activity, sulfasalazine may potentiate azathioprine toxicity. Finally, warfarin resistance has been noted in patients treated with azathioprine [51], [52].



DOSAGE AND MONITORING
Azathioprine is supplied for oral use as scored 50-mg tablets. The usual starting dose is 1 to 2 mg/kg per day in single or two divided dosages. One recent study of 48 children receiving azathioprine for atopic dermatitis initiated therapy at dose levels of 2.5 to 3.5 mg/kg in those with a normal TPMT level [53]. Therapeutic response for azathioprine occurs in 6 to 8 weeks. After 6 to 8 weeks, the dose may be increased by 0.5 mg/kg at 4-week intervals according to white blood cell counts and clinical response, and generally should not exceed 3 mg/kg per day. If there is no beneficial response in 12 to 16 weeks, treatment using azathioprine should be discontinued. There are no formal consensus guidelines for monitoring azathioprine when used for dermatologic indications. The current authors' recommendations have been adapted from published guidelines in the dermatologic literature [54] and are presented in Table 2.


Table 2 . Monitoring guidelines for the use of immunosuppressants Drug [Ref.] Monitoring tests Frequency Guidelines for dosage modification
Azathioprine [54] CBC with differential WBC and platelets Weekly ×4, every 2 wk ×2, then monthly Decrease dose if WBC < 4 × 109/L, platelets < 1011/L, discontinue if WBC < 2.5 × 109/L
Cyclophosphamide [54] CBC with differential WBC and platelets Weekly ×8, then monthly Decrease dose if WBC < 4 × 109/L, platelets < 1011/L, discontinue if WBC < 2.5 × 109/L
Renal function tests: BUN, creatinine Monthly
urinalysis weekly ×8, then every 2 wk, urine cytology when > 50 g total dose monthly Discontinue if hematuria
Liver function tests Monthly
Methotrexate [105] CBC with differential WBC and platelets Weekly ×2, every 2 wk ×2, then monthly Discontinue for 2–3 wk if WBC < 3.5 × 109/L, discontinue if WBC < 2.5 × 109/L or platelets < 1011/L, increased MCV necessitates folate administration
Renal function tests: BUN, creatinine Every 3–4 mo
Liver function tests Every 1–2 mo, ensure it is at least 1 week after most recent dose If persistently elevated, withhold for 1–2 wk and repeat; if elevation persists for 2–3 mo perform liver biopsy
Liver biopsy If no risk factors, at cumulative doses of 1.5 g, 3 g, and 4 g. If risk factors, then first at 2–4 mo of therapy, then at cumulative doses of 1–1.5 g, 3 g, 4 g. After a cumulative dose of 4 g, biopsy every 1–1.5 g.
Cyclosporine [189] CBC with differential WBC and platelets Every month, then every 2–3 mo
Renal function tests: BUN and creatinine (×3) Biweekly ×6, then monthly Decrease dose if creatinine increase is >30% over baseline; if persistent over 2 evaluations, discontinue
Blood pressure Biweekly ×6, then monthly
Urinalysis Biweekly ×2, then monthly
Liver function tests Biweekly ×2, then monthly
Potassium, uric acid, magnesium, cholesterol, triglycerides Biweekly ×2, then monthly
Creatinine clearance Not done routinely
MMF [207] CBC with differential WBC and platelets Weekly ×4, every 2 wk ×4, then monthly Decrease dose or discontinue if neutropenic

For all immunosuppressants, lymph node examination, complete physical examination, stool guaiac, skin cancer examination, and PAP smear every 6 mo are recommended.

Abbreviations: BUN, blood urea nitrogen; CBC, complete blood (cell) count; MCV, molluscum contagiosum virus; WBC, white blood cell (count).



CYCLOPHOSPHAMIDE
Cyclophosphamide is another cytotoxic agent used on occasion by dermatologists as an immune modulator. Because of the risk of bladder toxicity, myelotoxicity, gonadotoxicity, and malignancy, its use is reserved for serious and potentially life-threatening disorders in which the benefit outweighs the risks.



PHARMACOLOGY
Cyclophosphamide belongs to the nitrogen mustard family of alkylating agents. It was initially synthesized as an orally active form of chlorethamine (nitrogen mustard). It is well absorbed after oral administration, with peak plasma levels within 3 hours. The plasma half-life is 5 to 6 hours, with 12% to 14% of the drug being plasma bound [55]. The drug is metabolized by hepatic cytochrome P450 microsomal enzymes and oxidized to form the active metabolites phosphoramide mustard and acrolein. No consistent association between renal or hepatic insufficiency and cyclophosphamide toxicity has been found, and the drug can be metabolized independently of hepatic metabolism.

Phosphoramide mustard is the metabolite that alkylates DNA and inhibits DNA replication. Unlike azathioprine metabolites, the action of phosphoramide mustard is not S-phase specific and it can affect noncycling cells. There is a differential cytotoxicity to various lymphoid cell populations, with selective suppression of B cells [56]. Hence, this drug has its greatest effect in suppressing humoral immunity. Cyclophosphamide has a more variable response on cell-mediated immunity, and low-dose cyclophosphamide has been shown to potentiate immune responses in experimental systems. Immunostimulation has been related to increased IL-12 gene expression [57]. Variable effects on macrophages also have been noted [58].



ADVERSE EFFECTS


HEMATOLOGIC
Myelosuppression, consisting primarily of leukopenia, is the most common adverse reaction and can be dose-limiting. After intravenous (IV) administration, the nadir occurs at 8 to 12 days and recovery takes 18 to 25 days. A similar lag is noted with oral therapy. During the leukopenia, the patient is at increased risk of infection by pathogenic and opportunistic organisms. Thrombocytopenia and anemia occur less frequently.



GASTROINTESTINAL
Anorexia, nausea, and vomiting occur commonly with IV administration. These symptoms are dose-related and have been associated with the phosphoramide mustard metabolite. Oral ondansetron and dexamethasone have been shown to control nausea resistant to standard antiemetics in patients treated with IV cyclophosphamide for lupus nephritis [59]; however, a recent double-blind study of 258 patients undergoing emetic chemotherapy showed that a regimen of oral granisetron and oral dexamethasone did not achieve significantly better results than a course of metoclopramide, and that the former regimen was thus not cost-effective [60].



UROLOGIC
Urologic adverse effects are one of the major toxicities of this drug and can include dysuria, urgency, hematuria, bladder fibrosis, and necrosis [61]. Death from hemorrhagic cystitis has occurred. Hemorrhagic cystitis can develop at significantly lower dosages and with shorter durations of therapy in patients treated intravenously rather than orally. At the dose commonly used in dermatology, the average risk is 5% to 10% [62]. A review of 145 patients with Wegener's granulomatosis treated with oral cyclophosphamide at a dosage of 2 mg/kg, however, identified nonglomerular hematuria in 50% of patients (73 of 145) [63]. Nonglomerular hematuria occurred earlier in smokers and was chronic and recurrent in 38% of patients, even after discontinuation of the drug. Acrolein is the metabolite believed to be responsible for urotoxicity. Dehydration is an undisputed risk factor. High fluid intake and concurrent administration of mesna (sodium 2-mercaptoethane sulfonate) reduce the risk of this complication during IV administration. Mesna binds to acrolein in the bladder, producing an inactive compound that is eliminated in the urine. The relative efficacy of these two maneuvers is still a matter of debate [64].



ONCOGENIC POTENTIAL
Patients taking long-term oral cyclophosphamide have up to a 45-fold increase in the incidence of bladder cancer [65]. The estimated incidence of transitional cell carcinoma of the urinary tract, after first exposure to cyclophosphamide in patients who have Wegener's granulomatosis, was 5% at 10 years and 16% at 15 years [63]. Nonglomerular hematuria identified a subgroup at increased risk but was not invariably present. In patients who had RA and who were receiving oral cyclophosphamide, a 4-fold increase in solid tumors and a 16-fold increase in lymphoreticular malignancies have been observed [66], [67]. In a case-control study in which patients were followed up for 2 decades after treatment, the relative risk of cancer for those treated with cyclophosphamide was 1.5 and bladder cancer was noted as late as 17 years after discontinuation of the drug [68]. There was a recent report of a bladder carcinoma arising as late as 20 years after oral therapy with cyclophosphamide [69].



REPRODUCTIVE TOXICITY
Azoospermia and amenorrhea have been noted after both oral and IV pulse therapy. The incidence is as high as 50%, and risk factors include age, longer period of treatment, and degree of marrow suppression. Male patients may consider a sperm bank before treatment. A study of men given testosterone before and during an 8-month cycle of cyclophosphamide for nephrotic syndrome suggests that this method may help preserve fertility [70]. Suppressing ovarian function with oral contraceptives may protect the ovary, and some advocate the use of coadministering gonadotropins [71].



OPPORTUNISTIC INFECTIONS
Pathogenic and opportunistic infections can occur during treatment. They may occur in the absence of leukopenia. In a series of 100 patients with systemic lupus erythematosus, infections occurred with equal prevalence in those who received IV (39%) or oral (40%) medication. Risk factors for severe infections included a white blood cell count of less than 3000 and sequential IV and oral therapy [72].



MISCELLANEOUS
Anagen effluvium, mucositis, and hyperpigmentation have been reported. When used in higher dosages, cardiomyopathy, pneumonitis, pulmonary fibrosis, hepatotoxicity, and syndrome of inappropriate antidiuretic hormone also have been reported [61].



CLINICAL USE IN DERMATOLOGY
Cyclophosphamide continues to be used for potentially life-threatening dermatoses that are resistant to other forms of treatment. These may include systemic necrotizing vasculitis, severe forms of systemic lupus, severe blistering disorders, multicentric reticulohistiocytosis, relapsing polychondritis, and pyoderma gangrenosum [2]. Cyclophosphamide is believed to be a more effective steroid-sparing agent than azathioprine in the treatment of resistant pemphigus, although there is no incontrovertible evidence in the literature to support this view [33]. There are also reports describing successful cyclosphosphamide therapy in recalcitrant pemphigus foliaceous [73] and pemphigus vulgaris [74]. IV pulse cyclophosphamide is being used more frequently by dermatologists based on its effectiveness in lupus erythematosus nephritis [75]. With adequate hydration and use of mesna, the incidence of hemorrhagic cystitis is lower than with oral therapy, and it is hoped that the risk of cancer is lowered as well. Using a combination of dexamethasone pulse, cyclophosphamide pulse, and oral cyclophosphamide, clinical remissions have been claimed in 61 of 79 patients who have pemphigus [76]. The combined use of IV pulse and oral cyclophosphamide was recently reported in ocular pemphigoid [77] and in resistant bullous pemphigoid [78] to decrease total cyclophosphamide dose. A patient who had recalcitrant herpes gestationis also has responded to pulse IV cyclophosphamide after delivery of the infant [79]. A report of a patient with toxic epidermal necrolysis responding to IV cyclophosphamide [80] adds to the four cases in the literature [81]. The feasibility of outpatient monthly oral bolus cyclophosphamide therapy has been documented in patients with active lupus erythematosus [82]. Patients were instructed to maintain a fluid intake of 2 to 3 L per day and were given concurrent oral mesna. The safety and patient acceptance remain to be documented. The comparative efficacy and toxicities of pulse versus continuous oral administration in dermatologic conditions also remain to be determined. Reports of the successful use of oral cyclophosphamide in scleromyxedema [83] and in multicentric histiocytosis (in combination with methotrexate and corticosteroids) [84] add to the anecdotal literature of the use of this drug in rare, recalcitrant dermatoses.



USAGE GUIDELINES
Cyclophosphamide is contraindicated in patients who have demonstrated hypersensitivity, in pregnancy, and during breast feeding.



DRUG INTERACTIONS
Allopurinol increases the toxicity of cyclophosphamide through an unknown mechanism. There is a potential risk of increasing the incidence of lung toxicity in those taking amiodarone [85]. Drugs that alter the P450 system may affect cyclophosphamide pharmacokinetics.



DOSAGE AND MONITORING
Cyclophosphamide is supplied for oral use as 25- and 50-mg tablets. The recommended oral dosage is 1 to 3 mg/kg per day (50–200 mg/d). This drug should be taken in the morning followed by adequate hydration throughout the day (3 L of fluid/d). In monthly IV pulse therapy, 0.5 to 1.0 g/m2 is infused over 1 hour followed by vigorous IV hydration, and optional mesna usually at 160% of the cyclophosphamide dose separated into four doses at 0, 3, 6, and 9 hours. Some clinicians follow this treatment with daily oral cyclophosphamide at a dose of 50 mg/day. Further pulses are adjusted to obtain a white blood cell count nadir of 2 to 3 × 109 /L after 10 to 14 days. Monitoring guidelines are outlined in Table 2. It is recommended that all patients have a urinalysis every 3 to 6 months, even after the drug is discontinued, and that microscopic hematuria be evaluated by cystoscopy. Urine cytology should be done every 6 to 12 months, and routine cystoscopy should be considered every 1 to 2 years for all patients who have a history of microscopic hematuria [63].



METHOTREXATE
Methotrexate is a synthetic analog of folic acid that has been used in dermatologic therapy since 1951. Like azathioprine and cyclophosphamide, it has cytotoxic properties. There is now increasing evidence for separate mechanisms of anti-inflammatory activity.



PHARMACOLOGY
Methotrexate is usually given orally for the treatment of cutaneous disease but can be administered subcutaneously with similar kinetics [86]. Occasionally, this agent is given intramuscularly in the presence of gastrointestinal intolerance. There is marked variability in the bioavailability of oral methotrexate [87]. Approximately 35% to 50% of the drug is bound to albumin. Maximum blood levels occur 1 to 2 hours after oral and intramuscular administration [88], [89]. Polyglutamate derivatives are formed intracellularly and are the principal bioactive metabolites that are long lasting. Hepatic oxidation forms 7-hydroxy-methotrexate, a minor metabolite. The serum half-life is 6 to 7 hours for the methotrexate but much longer for the polyglutamate derivatives. The drug is excreted by the kidney, with 80% of a dose eliminated unchanged within 24 hours. Methotrexate is filtered by the glomeruli and then undergoes bidirectional transport within the renal tubule. Enterohepatic recirculation occurs to a minor degree.

Methotrexate binds intracellularly to dihydrofolate reductase, thereby preventing the reduction of folate cofactors (the conversion of dihydrofolate to tetrahydrofolate) and inhibiting the thymidylate synthesis. Methotrexate polyglutamates further inhibit thymidylate synthase and other folate-dependent enzymes, such as aminoimidazole-carboxamide ribonucleoside (AICAR) transformylase. Purine synthesis, required for DNA, RNA, and protein synthesis, is thereby inhibited. The methylation of homocysteine to methionine is inhibited, affecting the synthesis of polyamines such as spermidine and spermine [90]. Methotrexate may directly inhibit epidermal cell proliferation by these mechanisms, although lymphoid and macrophage cell lines have been shown to be much more susceptible to the growth inhibitory and cytotoxic effects of methotrexate than epidermal cell lines [91]. Recently, it has been shown that the mechanism of action of methotrexate is highly dependent on the production of reactive oxygen species [92]. In addition, the antimetabolite effect of methotrexate is primarily S-phase specific. The inhibition of AICAR transformylase is believed to lead to intracellular accumulation of AICAR, which leads to release of adenosine into the extracellular space [90], [93]. This process results, by way of interaction with specific cell surface adenosine receptors, in potent inhibition of polymorphonuclear chemotaxis and adherence and the inhibition of secretion of tumor necrosis factor α (TNF-α), IL-6, and IL-8 by monocyte/macrophages. This process may thus be responsible for the drug's anti-inflammatory effects. A recent study, however, downplays the role of adenosine release in the mechanism of action of methotrexate [94]. Inhibitory effects on IL-1, IL-2r, and the 5-lipoxygenase pathway also have been shown [95].



ADVERSE EFFECTS


HEMATOLOGIC
Cytopenia occurs in 10% to 20% of patients on long-term methotrexate for psoriasis manifesting as leukopenia, thrombocytopenia, or pancytopenia [96]. Potential risk factors include renal insufficiency, increased mean corpuscular volume, older age, and concomitant use of trimethoprim-sulfamethoxazole or nonsteroidal anti-inflammatory drugs (NSAIDs) [97]. The use of either folic acid (1–5 mg/d) or folinic acid (leucovorin, 2.5–5 mg, 24 h after the methotrexate) has been advocated to reduce hematotoxicity and is indicated in patients who develop macrocytosis [98]. In a survey of British dermatologists, 75% use folate supplementation in patients on methotrexate for psoriasis, one fourth of this group use it for all patients on therapy, and three fourths use it only in certain circumstances, namely in patients with macrocytosis [99]. The survey also revealed the wide variety of opinion that exists regarding the indications and dosing regimens for folate supplementation during methotrexate therapy and pointed to the need for further studies to establish better guidelines.



GASTROINTESTINAL
Nausea and vomiting are the most frequent adverse effects and are dose-related. Diarrhea and stomatitis may also occur. Folic acid administration, dose splitting, and parenteral administration may control symptoms [100]. Hepatotoxicity is a major concern, with a 7% overall risk of severe fibrosis/cirrhosis in patients with psoriasis but an apparent lower incidence in patients with RA [101], [102]. Risk factors include age, total dose, obesity, heavy alcohol intake, diabetes, and daily dosage [103]. Reports of severe fibrosis continue to be published and fibrosis may occur despite serial normal liver function tests [104]. Pretreatment complete blood count, liver function tests, and hepatitis A, B, and C serology should be performed [105], [106]. Baseline and serial liver biopsies are also sometimes performed, but in the absence of certain risk factors, such as history of liver disease or alcoholism and elevated liver function tests, the usefulness of a baseline biopsy is not recommended [105], [107], [108]. It has been suggested that serial biopsies may not be required in the absence of abnormal liver function tests if the initial biopsy sample is normal [109] or if the weekly dose of the drug is 15 mg or less [108]. One recent study, which emphasized the use of methotrexate in developing countries, claimed that for certain short-term methotrexate regimens in the treatment of psoriasis, the need for liver biopsies can be safely minimized [110]. Serial liver function tests continue to be recommended [105], however, and several authors promote the serial use of serum type III procollagen aminopeptide (PIIINP) as a test for fibrinogenesis [104], [111]. A recent 10-year retrospective study of 70 patients with psoriasis who were taking methotrexate showed that the presence of repeatedly normal levels of PIIINP on serial blood examinations correlated to a minimal risk of developing liver toxicity [112]; however, this screening technique has not yet found common usage or availability.



ONCOGENIC POTENTIAL
Methotrexate has been shown to be a significant independent risk factor (relative risk, 2.1) for developing squamous cell carcinoma (SCC) in patients with severe psoriasis [113], and this risk seems to be increased in patients with psoriasis who have undergone treatment with psoralen plus ultraviolet A (PUVA) [114]. Two patients with mixed-cellularity Hodgkin's disease have been reported in association with methotrexate use for psoriasis [115]. There also have been reports of an Epstein-Barr virus–associated lymphoproliferative disorder in patients on low-dose methotrexate [116], [117], [118]. Contrary to cyclophosphamide and azathioprine, methotrexate generally was not associated with an overall increased risk of lymphoma in a large-scale retrospective study of 16,263 patients with RA [119]. In addition, smaller retrospective studies found no increased risk of lymphoproliferative disease in patients with psoriasis on methotrexate [116].



REPRODUCTIVE TOXICITY
Methotrexate is a known abortifacient and teratogen. Teratologists have recommended a delay of at least 12 weeks between drug discontinuation and conception in women [120]. Conception should be avoided during therapy and 3 months afterward by couples in which the man is taking the drug [105].



OPPORTUNISTIC INFECTIONS
Opportunistic infections are reported in patients on low-dose methotrexate; in patients with RA on methotrexate, these infections seem to be more common than in those treated with azathioprine, cyclophosphamide, or cyclosporine [121]. Live vaccines should not be administered to patients on methotrexate.



MISCELLANEOUS
Idiosyncratic pneumonitis is rare in patients with psoriasis who are taking methotrexate, but it can be life threatening. A chest radiograph is warranted if pulmonary symptoms develop. Anaphylactoid reactions have been reported after low-dose methotrexate and can occur during initial exposure [122]. Painful erosion of psoriatic plaques is a cutaneous sign of methotrexate toxicity and occurred in two patients who had an alteration in methotrexate dosage and concomitant use of NSAIDs [123]. One report, however, described cutaneous ulceration that was attributed to methotrexate therapy in a patient without psoriasis [124]. Low-dose methotrexate may contribute to the development of stress fractures of long bone. One study recently reported on three patients on low-dose methotrexate with a triad of osseous pain, radiologic osteoporosis, and distal tibial stress fractures [125]. Alopecia, hyperpigmentation, UV burn recall, and toxic epidermal necrolysis also have been reported [89]. Central nervous system (CNS) toxicities, including headaches, dizziness, fatigue, and mood alterations, may occur.



CLINICAL USE IN DERMATOLOGY
The most widely accepted use for methotrexate in cutaneous disease is for the treatment of severe or refractory psoriasis. It is also used for pityriasis rubra pilaris, sarcoidosis, chronic urticaria, dermatomyositis, and lymphoproliferative diseases, such as pityriasis lichenoides et varioliformis acuta, lymphomatoid papulosis, and cutaneous T-cell lymphoma [89]. A recent review of clinical experience with low-dose methotrexate to treat 113 patients with severe psoriasis at a Dutch center revealed that prolonged improvement was achieved in 81% of patients [96]. The drug has been found to be of value in psoriatic polyarthritis as well [126]. In a case series of patients with adult pityriasis rubra pilaris, the combined use of retinoids and methotrexate has been advocated for patients whose disease is resistant to retinoids. Of 11 patients, 9 experienced significant clinical improvement at 16 weeks [127]. Others have warned against this combination over concern for the potential of increased hepatotoxicity, however [128]. A review of the use of methotrexate in 45 patients with lymphomatoid papulosis and Ki-1 lymphoma revealed satisfactory long-term control in 87% of patients with doses of 25 mg or less given at 1- to 4-week intervals for up to several years [129].

The use of methotrexate as corticosteroid-sparing agent in inflammatory dermatoses continues to receive attention. Kasteler and Callen [130] reported on the successful use of methotrexate (2.5–30 mg/wk) as a corticosteroid-sparing agent in 13 patients with dermatomyositis and therapy-resistant cutaneous features. Although older reports suggest methotrexate should be avoided in the treatment of pemphigus vulgaris [131], it has been used at a dose of 5 to 10 mg per week as an efficacious steroid-sparing agent in an elderly population with bullous pemphigoid [132]. There is a single case report claiming a steroid-sparing effect of methotrexate in the treatment of pyoderma gangrenosum [133]. There also has been some benefit shown in the treatment of widespread morphea [134]. Finally, a case report of multicentric reticulohistiocystosis responding to low weekly dosages of methotrexate in addition to prednisone adds to the two cases in the literature [135].



USAGE GUIDELINES
Patients with a history of significant liver or kidney disease should be excluded. The reader is referred to the published guidelines for use in patients with psoriasis [105] and, for comparison, to the guidelines for use in RA [101]. Pregnancy is an absolute contraindication, and active infection, excessive alcohol consumption, patient unreliability, anemia, leukopenia, and thrombocytopenia are all relative contraindications.



DRUG INTERACTIONS
Methotrexate toxicity has been precipitated by probenecid, trimethoprim-sulfamethoxazole, omeprazole, and penicillins, possibly by interference with tubular secretion, and possibly by interference with plasma protein binding of the methotrexate. Nephrotoxic drugs, such as NSAIDs, can reduce the renal clearance of methotrexate. Trimethoprim-sulfamethoxazole and possibly sulfasalazine may increase bone marrow toxicity. Concurrent use of nonabsorbed oral antibiotics, such as vancomycin, may decrease gastrointestinal absorption of methotrexate [87].



DOSAGE AND MONITORING
Methotrexate is commonly given either as a single weekly dose or in three divided doses over 36 hours. Usual dosages are from 5 to 10 mg/m2 per week (7.5–30 mg/wk). The drug is available orally as a 2.5-mg pill or can be given as a liquid (intended for injection). Monitoring guidelines are shown in Table 2.



CYCLOSPORINE
Cyclosporine is a lipophilic cyclic undecapeptide isolated from the fungus Tolypocladium inflatum. It has been used for the treatment of severe psoriasis since the early 1980s and has more recently found application in other inflammatory dermatoses. Unlike the three previous immunomodulatory drugs, this drug's main effect is on the intracellular signal transduction pathways of cells that are primarily of the lymphoid lineage.



PHARMACOLOGY
Cyclosporine is insoluble in water. In a traditional formulation, given orally as a soft gelatin capsule, the absorption is erratic, with a bioavailability of approximately 30%, with high interpatient and intrapatient variability [136]. Peak blood levels occur after 2 to 4 hours, with an average serum half-life of 18 hours. Tissue concentrations are highest in adipose tissue and 80% of the drug is bound to lipoproteins. There is poor CNS penetration. The drug is metabolized by the cytochrome P450 3A system with bile excretion and enterohepatic recirculation. Metabolites are inactive and only 6% of the drug is excreted in the urine in the form of metabolites.

The microemulsion formulation of cyclosporine is now the standard formulation in Canada and Europe. It is absorbed more rapidly, with a peak serum concentration at 1 hour earlier than the original formulation, and has an increase in bioavailability, resulting in higher maximum concentrations and lower intrapatient and interpatient variability [137]. This effect is associated with an increase in clinical efficacy [138] and in a comparable safety profile. A decreased tolerability with a 1:1 dose conversion has been noted with an increase in reported gastrointestinal adverse effects [137]. A 1:1 dose conversion is still recommended when converting patients from the original formulation to the microemulsion formulation, however [139]. Use of the new formulation seems to result in an improved outcome at a lower dosage [140].Cyclosporine acts primarily on T cells. The drug forms a complex with cyclophilin intracellularly, which then binds to and inhibits calcineurin. This process prevents the activation of nuclear factors involved in the transcription of genes encoding several cytokines, including IL-2 and interferon γ (IFN-γ) [141], [142]. This process then results in the inhibition of T-cell activation and of T-cell–mediated potentiation of the immune response.



ADVERSE EFFECTS


NEPHROTOXICITY AND HYPERTENSION
Cyclosporine can cause structural and functional changes in the kidney. Functional changes are caused by dose-related vasoconstriction in the renal microcirculation. Structural changes include an obliterative microangiopathy with tubular atrophy and interstitial fibrosis [143]. A recently proposed mechanism of nephrotoxicity is that cyclosporine, through the inhibition of the adaptive response to hypertonicity, interferes with the urinary concentration mechanism [144]. Risk factors include a daily dose of more than 5 mg/kg, persistent elevations of creatinine to more than 30% of baseline, and older age [145]. Structural changes may also correlate with drug-induced hypertension [146] and can even occur with low-dose cyclosporine [147], [148]. Hypertension is seen in 10% to 15% of patients. This condition is reversible with drug discontinuation and can be controlled with calcium channel blockers [149], [150]. Studies in animal models have shown that such supplements as magnesium [151], glycine [152], and L-arginine [153] may reduce the risk of nephrotoxicity.



ONCOGENIC POTENTIAL
Cyclosporine is not mutagenic, but immunosuppression results in an increased risk of skin cancers and possibly lymphomas. There have been reports of lymphomas occurring while patients were taking cyclosporine [154], although some authors believe that these cases of lymphoma were not directly related to the cyclosporine, and that cyclosporine use in psoriasis does not necessarily convey an increased risk of lymphoma [155]. The increased risk in skin cancers has been estimated from 2.6-fold in patients with RA to 7.5-fold in patients with psoriasis [139]. A recent prospective study of 1252 patients with severe psoriasis on cyclosporine therapy showed a sixfold increase in cutaneous malignancy attributable to cyclosporine [156]. This study also noted that the increased risk for cutaneous malignancy was apparent after 2 years of therapy. Previous PUVA therapy and previous immunosuppressive therapy may be predisposing factors in the development of skin cancer in patients with psoriasis [156], [157].



MISCELLANEOUS
Hyperlipidemia, hyperkalemia, hypomagnesemia, and hyperuricemia can occur but are usually mild. Neurologic side effects can include hand tremors, paresthesias, dysesthesias, and headache. Mucocutaneous side effects include gingival hyperplasia, hypertrichosis, pilomatrix dysplasia, facial dysmorphism, acne, eruptive angiomas, and folliculitis. Transient nausea, vomiting, diarrhea, abdominal discomfort, and severe fatigue also have been noted.



CLINICAL USE IN DERMATOLOGY
Cyclosporine has become an accepted treatment for severe psoriasis and atopic dermatitis. The efficacy of its use as maintenance therapy in severe psoriasis has been shown [158], and the safety of cyclosporine in the treatment of psoriasis for up to 2 years has been documented [159]. It is effective for psoriatic arthritis as well, although symptomatic improvement can be slow [160]. Strategies to minimize risk and optimize treatment include intermittent short-course therapy, rotational therapy, and short-term use for crisis management [139], [161]. Cyclosporine is safe and effective for the short-term treatment of severe atopic dermatitis [162]. In an open trial, 65 of 100 patients completed 48 weeks of therapy with significant improvement at an average dose of 3 mg/kg per day [163]. A more recent study has shown that cyclosporine microemulsion is effective for the short-term treatment of severe atopic dermatitis using a bodyweight-independent dosing scheme [164]. The study results also showed that a starting dose of 150 mg per day was preferable to a starting dose of 300 mg per day, mainly because the former was observed to be much less nephrotoxic. As with psoriasis, relapses are the rule, but a fraction of patients have prolonged remissions [165]. The efficacy of cyclosporine at 3 mg/kg per day in recalcitrant hand dermatitis was similar to topical betamethasone dipropionate in a randomized double-blind study [166].

The use of cyclosporine in other dermatoses is based mostly on case reports and case series of successful outcomes. These have been summarized in review articles on the subject [167], [168], [169]. Cyclosporine is considered by some to be first-line treatment for pyoderma gangrenosum [168]. It is also excellent treatment for extensive cutaneous lichen planus and may result in prolonged remission even at very low dosages (1–5 mg/kg/d) [170]. Oral and genital lichen planus may be somewhat less responsive [1]. Reports of the efficacy of cyclosporine in the bullous disorders are mixed. In one report, long-lasting remissions were obtained in six patients with pemphigus vulgaris refractory to corticosteroids and other immunosuppressive agents [171]; however, a study comparing prednisone alone with prednisone plus cyclosporine and prednisone plus cyclophosphamide for the treatment of oral pemphigus found no significant difference between the groups [172]. A more recent study showed that combination treatment with corticosteroids and cyclosporine (at 5 mg/kg) offers no advantage over treatment with corticosteroids alone in patients with pemphigus [173]; however, some maintain that there is value in using cyclosporine as maintenance therapy for pemphigus [174]. Several case reports document the efficacy of cyclosporine as a steroid-sparing agent in bullous and cicatricial pemphigoid, and in epidermolysis bullosa acquisita [1]. Acute and juvenile dermatomyositis respond to cyclosporine, and the drug should be considered in severe or refractory disease [175]. Dramatic improvement also has been seen in the mucocutaneous manifestations of Behçet's disease [168]. Cyclosporine in addition to low-dose prednisone yielded cosmetically acceptable results in only two of eight patients treated for alopecia areata in a recent report without induction of durable remissions [176], and therefore does not seem warranted for this indication. Recent reports have suggested impressive responses in the treatment of severe cytophagic histiocytic panniculitis [177], toxic epidermal necrolysis [178], hidradenitis suppurativa [179], and prurigo nodularis [180]. Further study is warranted in these diseases. Also, there are reports of the successful use of cyclosporine in the following conditions: actinic reticuloid, Hailey-Hailey disease [181], granuloma annulare [182], [183], chronic actinic dermatitis [184], recurrent Reiter's syndrome [185], eosinophilic cellulites [186], and Sweet's syndrome [187].



USAGE GUIDELINES
Guidelines for the use of cyclosporine in psoriasis have been published [139], [188], [189] and can be adopted for the use of cyclosporine in other dermatoses. Absolute contraindications are severe concurrent infection, uncontrolled hypertension, or renal insufficiency. Relative contraindications include the following: current or past malignancy, immunodeficiency, high risk of noncompliance, use of concomitant nephrotoxic drugs, gout, liver disease, and pregnancy [189].



DRUG INTERACTIONS
Cyclosporine, in either oral formulation, interacts with many drugs [139]. Most of the clinically relevant drug interactions with cyclosporine relate to competitive inhibition or induction of the cytochrome P450 3A microsomal enzymes. Anticonvulsant agents (phenytoin, phenobarbital, carbamazepine), antibiotics (rifampin, trimethoprim-sulfamethoxazole, nafcillin), and phenylbutazone can decrease cyclosporine levels; other antibiotics (erythromycin, doxycycline), antifungal agents (ketoconazole, itraconazole, fluconazole), calcium channel blockers (verapamil, diltiazem, nicardipine), steroid hormones, and diuretics (furosemide, thiazides) can increase cyclosporine levels. Several drugs may also synergistically increase cyclosporine nephrotoxicity (diuretics, NSAIDs, aminoglycosides, trimethoprim-sulfamethoxazole, amphotericin B, and melphalan).



DOSAGE AND MONITORING GUIDELINES
The microemulsion formulation is available in 25-mg, 50-mg, and 100-mg capsules. The recommended starting dose [189] for patients with stable, generalized psoriasis or for patients whose disease severity lies between moderate and severe is 2.5 mg/kg per day in one or two divided doses. If improvement is not noted within 2 to 4 weeks, the cyclosporine dose can then be increased in increments of 0.5 to 1.0 mg/kg per day every 2 weeks to a maximum of 5 mg/kg per day. For patients in whom a rapid improvement is critical (ie, those with severe, inflammatory flares of psoriasis or the presence of other diseases that have failed previous therapies), the starting dose should be 5 mg/kg per day. (Note: the US Food and Drug Administration [FDA] has decreased the upper-limit dose for cyclosporine treatment of psoriasis to 4 mg/kg/d.) In this scenario, as soon as the patient has a significant response, the dose can be decreased by 0.5 to 1 mg/kg per day every week until the minimum effective maintenance dose is attained. Monitoring guidelines are presented in Table 2. In either the high- or low-dose scheme, dosage adjustments should be made in response to adverse effects. If, for instance, the serum creatinine level increases by more than 30% above baseline, and a repeat creatinine level 2 weeks later still shows the increase, the dose of cyclosporine should be decreased by at least 1 mg/kg per day, with the creatinine level to be rechecked in 1 month. If, at that point, serum creatinine decreases to less than 30% above the patient's baseline, treatment can be continued, and if not, then therapy should be discontinued and not resumed until the creatinine levels return to within 10% of the patient's baseline. Another adverse effect is an increase in blood pressure. When this occurs, the physician can either attempt to control this through antihypertensive therapy or by decreasing the cyclosporine dose by 25% to 50% [189].



MYCOPHENOLATE MOFETIL
Mycophenolate mofetil (MMF) is a morpholinoethyl ester of mycophenolic acid (MPA) [190], which, on biotransformation after absorption, converts to MPA, the active metabolite. As an immune suppressant, MMF has been widely applied in organ transplantation medicine since the early 1990s. More recently, it has found other clinical applications in dermatology, rheumatology, and gastroenterology.



PHARMACOLOGY
MMF, or 2-morpholinoethyl (E)-6-(1,3-dihydro-4-hydroxy-6-methoxy-7-methyl-3-oxo-5-isobenzofuranyl)-4-methyl-4-hexenoate, is the 2-morpholinoethyl ester of MPA. It is rapidly absorbed following oral administration and then undergoes ester hydrolysis in the liver to form mycophenolic acid, the active metabolite [191], [192]. Its oral bioavailability is high at 94.1% in healthy volunteers [193]. The active metabolite MPA is a noncompetitive inhibitor of the cellular inosine monophosphate dehydrogenase required for de novo purine biosynthesis [190], [194], [195]. As a result, it blocks RNA and DNA synthesis, which is critical for the immune response. Because the lymphocytes rely predominantly on de novo purine biosynthesis rather than the salvage pathway for purine synthesis (HGPRT), the T- and B-cell proliferative response is inhibited [196], [197]. Therefore, MMF inhibits antibody production and the formation of cytotoxic T lymphocytes [190], [195]. The selectivity for lymphocytes has another mechanism. MPA is 5 times more active against the type 2 isoform of inosine monophosphatase dehydrogenase (IMPDH), which is activated in activated lymphocytes, than against the type 1 IMPDH, which is active in most cell types [198]. Once ingested, MPA has a half-life of 17.9 hours in healthy volunteers, and as part of its metabolism, it undergoes glucuronidation to form phenolic glucuronide of MPA, which is not pharmacologically active. Most of the metabolite (93%) is excreted in the urine, with 6% excreted in the feces.



ADVERSE EFFECTS
The reported side effects of MMF are mainly related to gastrointestinal and hematologic systems, with little effect on hepatic and renal function [199], [200]. The side-effect profile makes MMF highly complementary to many other immune suppressants used for dermatologic diseases, such as cyclosporine, methotrexate, cyclophosphamide, and azathioprine, which have renal or hepatic toxicities [1].



GASTROINTESTINAL
The most common side effects of MMF include nausea, vomiting, diarrhea, and abdominal cramps, with an incidence of 12% to 36% [201]. In a recent study of MMF in 54 patients with systemic lupus, 39% of patients had gastrointestinal adverse events [202]. Recently, it has been suggested that MMF caused erosive enterocolitis in renal transplant patients receiving the drug; however, a direct, causal link has not been established [203]. If gastrointestinal symptoms develop, the daily dose can often be spread over more than two daily doses. If adverse effects persist for a longer period of time and seem more serious, MMF may have to be withdrawn while a comprehensive invasive diagnostic process is performed to rule out any opportunistic infections. Severe gastrointestinal complications with MMF are rare, but when they do occur they may require extensive diagnosis and treatment [204].



HEMATOLOGIC
For 11% to 34% of patients, the most serious hematologic side effect is leukopenia. Severe leukopenia is only present in 0.5%–2.0% of patients. These effects are generally reversible on drug discontinuation [201], [205]. In a study of 57 patients who underwent liver transplants, approximately half received MMF, and the rest received azathioprine [206]. Of the MMF-treated patients, 21% had thrombocytopenia, whereas leukopenia was seen in 7% of MMF-treated patients. Both of these adverse effects occurred less frequently with MMF than with azathioprine.



ONCOGENIC POTENTIAL
In a clinical trial involving 1483 patients enrolled for the prevention of renal transplant rejection, there was a slight increase of lymphoproliferative malignancies in the MMF group after more than 1 year (incidence, 0.6%–1.0%) on therapy compared with placebo or azathioprine (incidence, 0.3%) [201]. The 3-year safety data showed no unexpected changes in malignancy incidences compared with the 1-year data [207]. In a recent retrospective examination of 106 renal transplant patients receiving azathioprine and 106 receiving MMF, four patients using azathioprine were diagnosed with a malignancy (three post-transplant lymphoproliferative disorders, one SCC) compared with two MMF patients (prostate cancer, basal skin cell carcinoma) [208]. In a more recent 3-year safety study of 128 renal transplant patients, there were slightly more malignancies (predominantly cutaneous) in patients given MMF (14.2%) versus those patients on azathioprine (10.2%) [209]. In the previously described studies involving transplant patients, however, the different patient groups in these studies were all taking cyclophosphamide as well, so the above numbers are relevant only in that they convey the risk of neoplasm from MMF relative to azathioprine.



INFECTIONS
Because MMF is an immune suppressant, it has been associated with increased infection rates in patients, primarily herpetic viral infections, with a relative risk of 2 to 3 times normal rates [205]. The studies that showed an increased risk of infection primarily reported on transplant patients. A recent retrospective study of 23 transplant patients on 2 g of MMF per day of MMF showed 10 patients developing 22 opportunistic or serious viral or bacterial infections [210]. The link of MMF specifically to cytomegalovirus (CMV) infection is more controversial. One study on transplant patients found that the addition of MMF to the cyclosporine-prednisone combination did not result in an increase in primary CMV infections, but CMV infections led more often to CMV disease in patients treated with MMF than in those not receiving MMF [211]. In a similar study, MMF did not increase the overall incidence of CMV infection in renal transplant patients but increased the severity of CMV infection in terms of the frequency of organ involvement and number of organs involved [212]. More recently, however, a study of 48 patients showed that MMF puts transplant patients at a significant increased risk (with a calculated relative risk of 19) of a CMV infection [213].



CLINICAL USE IN DERMATOLOGY
The primary indication for MMF is for the prophylaxis of organ transplant rejection, in combination with cyclosporine and corticosteroids [201]. Since the report of the successful treatment of bullous pemphigoid and phemphigus vulgaris with MMF in 1997 [214], [215], however, dermatologic applications of this new immune suppressant have been expanded to many other bullous and inflammatory conditions. Also since this initial report, other reports have confirmed the usefulness of MMF for treating bullous pemphigoid [216], [217], [218], [219]. Similarly, other bullous disorders have been reported to be responsive to MMF, including pemphigus vulgaris [214], [217], [220], [221], pemphigus foliaceous [222], bullous and hypertrophic lichen planus [223], linear IgA bullous dermatosis [224], cicatricial pemphigoid [225], and paraneoplastic pemphigus [226], [227]. Epidermolysis bullosa acquisita failed to respond to a combination treatment of MMF and prednisone in one report [227],but succeeded in another [228]. A recent case series of 17 patents with pemphigus (12 with pemphigus vulgaris, 4 with pemphigus foliaceous, and 1 with paraneoplastic pemphigus) treated with MMF showed improvement in 12 patients [229]. In general, most of the reports are on combinations of MMF and glucocorticoids. One exception is the report of successful treatment with MMF monotherapy of a patient who had pemphigus vulgaris [220]. The dosages in these reports ranged from 2 to 3 g per day, and patients generally tolerated the treatment well. In addition, MPA was used in the 1970s for the successful treatment of psoriasis [230].

Since MMF became available clinically in the early 1990s, Haufs et al [231] reported that one patient responded to MMF at a dosage of 1 to 1.5 g twice daily in 6 weeks, with a 50% reduction in Psoriasis Area and Severity Index (PASI) score. Subsequently, Nousari et al [218] reported on another patient with plaque psoriasis who responded to MMF plus topical steroid and calcipotriol. In a series of five patients with plaque-type psoriasis taking 1 g of MMF twice daily for 10 weeks, two patients with mild to moderate disease showed improvement, whereas those with severe psoriasis did not respond [232]. In a study of 11 patients with severe, stable plaque-type psoriasis, it was shown that MMF at dosages of 1 g twice daily for 3 weeks was an effective and seemingly safe treatment option [233]. In a more recent study, 23 patients with moderate to severe psoriasis were treated with MMF at a dosage of 2 to 3 g per day for 12 weeks in an open-label uncontrolled trial; approximately three fourths of the patients were observed to have a significant reduction in symptom scores, with only few adverse events [234]. MMF (2–3 g/d) has been used in combination with cyclosporine for the treatment of recalcitrant pyoderma gangrenosum [235], [236], [237], [238]. Grundmann–Kollmann et al [239] reported on two patients with severe atopic dermatitis who dramatically responded to MMF monotherapy after 2 to 3 weeks, with no side effects. The effectiveness of MMF for atopic dermatitis was supported in two separate pilot studies, each involving 10 patients with moderate-to-severe or severe atopic dermatitis [240], [241]. In another report, however, none of the five patients with atopic dermatitis responded to MMF [242]. Pickenacker et al [243] reported on a patient with severe dyshidrotic eczema who responded to MMF at a dosage of 3 g per day, but in another report, a patient apparently developed dyshidrotic eczema while on MMF therapy [244]. Clinical experiences have been reported for successful treatment of systemic [245], [246], [247], [248], subacute cutaneous [249], and discoid [250] lupus erythematosus, and other dermatologic diseases, including vasculitis [251], [252], [253], [254], [255], sarcoidosis [256], ulcerated necrobiosis lipoidica [257], and dermatomyositis [258]. Almost all of the reports of the effectiveness of MMF in patients with dermatologic diseases are case reports, case series, or small-scale, uncontrolled clinical trials.



USAGE GUIDELINES
MMF is contraindicated in patients with hypersensitivity to MMF, MPA, or any component of the drug product [201], [207]. It is also contraindicated in pregnancy. Caution should be exercised in patients with gastrointestinal disorders because rare gastrointestinal bleeding has been reported. Patients with severe renal function impairment (glomerular filtration rate of < 25 mL/min/1.73 m3) should not receive more than 2 g of MMF per day [201].



DRUG INTERACTIONS
No major drug interactions have been reported. Although there is some evidence to suggest that glucocorticoids interfere with the bioavailability of MMF [259], it is unclear as to the clinical significance of this phenomenon. The coadministration of MMF with antacids, iron, and cholestyramine causes a reduction of MMF absorption [201], [260]. One case report attempted to ascribe the cause of a patient's neutropenia to an interaction between MMF and valacyclovir [261]. Also, because of its similar effects on purine metabolism and bone marrow suppression, MMF should not be used concomitantly with azathioprine.



DOSAGE AND MONITORING
MMF is available as 250- and 500-mg tablets. Typical daily dosages are 2 to 3 g per day in twice-daily dosing. Although MMF has been used in dermatologic conditions, official approval for its use in the treatment of such diseases is still not available. There are therefore no formal consensus guidelines for monitoring MMF when used for dermatologic indications. The current authors' recommendations have been adapted from previous guidelines [207] and are presented in Table 2. Recent literature has suggested a possible benefit in monitoring serum levels of MMF in transplant patients, but the relationship between pharmacokinetic parameters and adverse events remains unclear [262].



THE USE OF SYSTEMIC IMMUNOBIOLOGIC AGENTS
Alefacept, efalizumab, etanercept, and infliximab are currently the immunobiologic agents most commonly used in dermatology. At present, within the dermatologic therapeutic armamentarium, these therapies are used mainly for the treatment of psoriasis and psoriatic arthritis; however, their utility has been shown in several other cutaneous disorders as well. A focus on the use of these agents for the treatment of psoriasis, with anecdotal commentary on other disease-specific clinical applications of these medications, and the pharmacology, mechanism of action, dosages, and side-effect profiles of these drugs will allow for a more thorough understanding of these agents for the treatment of cutaneous disease.

A greater understanding of the role that T lymphocytes play in the pathogenesis of cutaneous inflammatory disease has transformed physicians' understanding of the mechanism of these disorders and resulted in a therapeutic revolution. It is now understood that psoriasis, for example, is an autoimmune disease, with an unknown antigenic stimulus. The epidermal hyperplasia of psoriasis is a CD8+ and CD4+ T-lymphocyte–mediated reaction that occurs within focal skin regions [263]. Much of the current understanding of this process has come from experiments using the severe combined immunodeficiency, or SCID, mouse model of psoriasis in which clinically normal skin from a patient with psoriasis is transplanted onto an immunodeficient mouse. When syngeneic T cells are activated in vitro and injected into the transplanted skin, the skin develops a phenotypic expression nearly identical to psoriatic skin [264], [265]. These experiments have confirmed the paramount role of activated T cells in the induction of the psoriasis plaque. Furthermore, studies using monoclonal antibodies have elucidated the specific subsets of T cells involved in the formation and maintenance of the psoriasis plaque and their roles at precise sites within psoriatic skin. For example, CD8+ T cells (mainly cytotoxic or “killer lymphocytes”) are found in high concentrations in the epidermis, whereas CD4+ T cells predominate in the dermis [266], [267]. Psoriasis is considered to be a Th1 immune disease because in psoriasis both CD4+ and CD8+ T cells produce mainly type 1 cytokines. The understanding of the Th1 phenotype has facilitated the creation of therapies that target specific steps within the Th1 pathway. Many now recognize psoriasis to be one of the most prevalent T-cell–mediated inflammatory diseases in humans, and it is considered to be the model Th1 immune disorder by many researchers [263], [268].

The understanding of the T-cell–mediated pathogenesis of psoriasis has resulted in an explosive research effort toward the development of biologic therapies designed to target the immunologic process at specific points along the inflammatory cascade. The biologics can be divided into three classes of agents: (1) recombinant human cytokines or growth factors, (2) monoclonal antibodies, and (3) fusion proteins. The classes and mechanism of action of the four most commonly used immunobiologic agents used in dermatology are outlined in Table 3. Alefacept, efalizumbab, etanercept, and infliximab, examples of the latter two kinds of biologic agents, target highly specific steps in the aforementioned T-cell–mediated inflammatory cascade. These therapies therefore are able to control psoriatic disease with minimal impairment of immune function and significantly fewer side effects than traditional immunosuppressive agents.


Table 3 . Summary of the common immunobiologic agents used in dermatology Features Alefacept (Amevive) Efalizumab (Raptiva) Etanercept (Enbrel) Infliximab (Remicade)
Type of agent Fusion protein Humanized monoclonal antibody Fusion protein Chimeric monoclonal antibody
Mechanism of action Blocks T-cell activation. Selective reduction of memory effector T cells Anti CD11a blocks T-cell activation and reduces trafficking of T cells to inflamed skin TNF-α inhibitor TNF-α inhibitor
Route of administration IM SC SC IV
Approval status Psoriasis: FDA approved for chronic moderate to severe plaque-type psoriasis, January 2003 Psoriasis: FDA approved for chronic moderate to severe plaque-type psoriasis, October 2003 Psoriasis: FDA approved for chronic moderate to severe plaque-type psoriasis, April 2004 Psoriasis: Phase 3

Abbreviation: IM, intramuscular.



ALEFACEPT


PHARMACOLOGY/MECHANISM OF ACTION
Alefacept is given as an intramuscular injection in a dose containing 15 mg of alefacept per 0.5 mL of reconstituted solution. In patients who received alefacept as a 7.5-mg IV administration, the mean volume of distribution was 94 mL/kg, the mean clearance was 0.25 mL/kg per hour, and the mean elimination half-life was approximately 270 hours. Bioavailability was found to be 63% post-intramuscular injection [269]. The pharmacokinetics of alefacept in pediatric patients has not been studied. The effects of renal or hepatic impairment on the pharmacokinetics of alefacept also have not been studied.

Alefacept is a fusion protein consisting of the first extracellular domain of human leukocyte function antigen-3 (LFA-3) fused to the hinge Ch2 and Ch3 sequences of human IgG1 [268]. The drug is produced by recombinant DNA technology in a Chinese hamster ovary mammalian cell expression system [269]. Alefacept acts as an immunosuppressive agent by inhibiting T-cell activation and proliferation by binding to CD2 on T cells and blocking the LFA-3–CD2 interaction [270], [271], [272]. Alefacept also engages FcγRIII IgG receptors (on NKCs and macrophages), resulting in the apoptosis of T cells that express high levels of CD2 [264]. Because CD2 expression is higher on activated memory (CD4+ CD45RO+ and CD8+ CD45R0+) than on naive (CD45RA+) T cells, alefacept produces a selective reduction in memory T cells [268], [273], [274], [275], [276].

Because the targeting of memory T cells is selective, naive (CD45RA+) populations are minimally affected. This situation allows patients to maintain the ability to mount appropriate immune responses to infectious agents [277]. This result was shown when alefacept-treated patients and controls were able to mount comparable antibody responses to immunization with a novel T-cell–dependent antigen (bacteriophage phiX174) and a recall antigen (tetanus toxoid) [278].

The T-cell reductive effect observed in the circulation has been shown in the skin. Patients with psoriasis who were treated with alefacept showed decreased activation of T cells and memory T cells and a reduction in IFN-γ production in lesional skin [279], [280]. Because the skin takes time to repopulate, by selectively targeting the epidermal T cells, alefacept is able to induce longer lasting remissions than many other biologic agents.



ADVERSE EFFECTS


ONCOGENIC POTENTIAL
The package insert for alefacept warns that the drug may increase the risk of acquiring a malignancy. No statistically significant increased incidence of malignancy has been observed in any studies to date, however. In a study that looked at repeat courses of alefacept, five cases of malignancies (two systemic, three cutaneous) were reported [281]. In each case, the patient had additional potential risk factors for developing a malignancy, and the overall incidence of cancers in the study was similar to what would be statistically expected in untreated individuals of the same age. As is true of all of the biologic agents, alefacept is a novel therapy, and the adverse effect profile may not be established until after years of clinical experience. Patients with a history of systemic malignancy should not be treated with alefacept.



INFECTIONS
One or two 12-week courses of intramuscular alefacept were shown in phase 3 studies to have safety and tolerability profiles similar to placebo [281]. No increase in the incidence of opportunistic infections was noted [282]. No association between infections and CD4+ T-cell counts was observed. In the largest phase 3 trial, the only adverse event that occurred with an incidence of 5% or more in the alefacept group versus the placebo group in course 1 was chills (10% versus 1%) [283]. The incidence of chills was temporally related to dosing. Chills tended to occur soon after dosing, and the frequency of chills was lower in the second course. Of note, chills were not a side effect in the other large-scale phase 3 study [282] that examined the efficacy and tolerability of intramuscular alefacept, and this side effect can therefore most likely be attributed to the IV route of administration, which is no longer available. In course 2 of the aforementioned phase 3 trial, accidental injury and pharyngitis were the only adverse events that occurred with an incidence of 5% or more in the alefacept group versus the placebo group (20% versus 15%, and 16% versus 11%, respectively) [283].

Alefacept is an immunosuppressive agent and therefore should not be administered to patients with clinically significant infections. To avoid clinically significant immunosuppression, other immunosuppressive agents should be avoided or used with caution in patients receiving alefacept. If a patient develops a serious infection, alefacept should be discontinued and the patient should be closely monitored. Therapy can be reinitiated on resolution of infection at the physician's clinical discretion.



EFFECTS ON THE IMMUNE SYSTEM
The biologic agents, as with any exogenous protein molecule administered as therapy, have the potential for immunogenicity. Antibody titers were low (< 1:40) in both of the largest phase 3 trials, and no immune hypersensitivity reactions occurred [282], [283].



INJECTION SITE REACTIONS
In the largest phase 3 clinical trial that evaluated the intramuscular route of administration, injection site pain and injection site inflammation were adverse events that occurred at least 5% more frequently in alefacept-treated patients than in those taking a placebo. Injection site reactions were typically classified as mild, were usually single episodes, and did not result in any patient discontinuing the study [282].



SUMMARY OF EFFICACY DATA FROM IMPORTANT CLINICAL TRIALS
Two important randomized, double-blind, placebo-controlled phase 3 trials were conducted to evaluate the efficacy and tolerability of alefacept. In the first trial, two 12-week courses of once-weekly 7.5-mg IV alefacept versus placebo were given in a randomized double-blind study, and patients were followed up for 12 weeks after each treatment course [283]. Clinical outcomes were measured as follows: a 75% or more reduction in the PASI, a 50% or more PASI reduction, or a Physician Global Assessment (PGA) of “clear” or “almost clear” [283]. Because many patients show continued clinical improvement after cessation of therapy as shown by phase 2 data [276], the overall response rate was evaluated during both the 12-week treatment period and during the 12-week follow-up period.

Of patients treated during course 1, 28% achieved a 75% or greater reduction in PASI as compared with 8% of placebo-treated patients (P < 0.001); of those who achieved a 75% or greater reduction in PASI, 23% achieved a PGA of clear/almost clear as compared with 6% of placebo-treated patients (P < 0.001). Of patients treated during course 1, 56% achieved a 50% or greater reduction in PASI as compared with 24% of placebo-treated patients (P < 0.001).

A second course of alefacept provided additional benefit. Of patients who received two 12-week courses of alefacept, 40% achieved a 75% or greater reduction in PASI, 71% achieved a 50% or greater reduction in PASI, and 32% achieved a PGA of clear/almost clear. Patients who were treated with two courses of alefacept had a maximum mean reduction of 54% from baseline PASI at 6 weeks post treatment [283].

The data showing that alefacept produced durable clinical improvements among patients who responded were significant. Those patients, who received a single course of alefacept and achieved 75% or greater overall PASI reduction, were able to maintain a 50% or greater reduction in PASI for a median duration of more than 7 months. Patients who achieved a PGA of clear or almost clear maintained a 50% or greater reduction in PASI for a median duration of approximately 8 months. Two courses of alefacept resulted in a greater duration of response than a single course. This durable response makes alefacept the only psoriasis therapy besides PUVA [284], the Goeckerman regimen [285], [286], and possibly UVB [287] that can be considered a remittive treatment. Psoriasis therapies can be either suppressive, where symptoms of disease recur shortly after withdrawal of therapy, or remittive. Remittive therapies, such as alefacept, provide long-lasting remission by mechanisms that reduce T cells in the skin.

In the other pivotal phase 3 trial, the first randomized controlled trial of weekly intramuscular doses of alefacept, 507 patients were randomized to one of three treatment groups (10 mg, 15 mg, or placebo) of intramuscular alefacept administered once weekly for 12 weeks with a 12-week follow-up [282]. To assess overall response rate, the clinical outcome was measured throughout both the treatment and follow-up periods as follows: a 75% or greater PASI reduction, a 50% or greater PASI reduction, or a PGA of clear/almost clear. Response rates were compared among dosage groups.

The percentage of patients who achieved a 75% or greater reduction in PASI was significantly higher (P < 0.001) in patients who received 15 mg of alefacept (33%) or 10 mg of alefacept (28%) as compared with the placebo group (13%). Of patients who achieved a 50% or greater PASI reduction throughout the study period, 57% were in the 15-mg alefacept group (P < 0.001 versus placebo), 53% were in the 10-mg alefacept group (P = 0.002 versus placebo), and 35% were in the placebo group (P < 0.001). Overall response rates for a PGA of clear or almost clear were 24%, 22%, and 8% of patients in the 15-mg, 10-mg, and placebo groups, respectively (P < 0.001 for comparisons of both doses of alefacept versus placebo). Again, the clinical response was durable and attributed to the drug's mechanism of action. Of patients in the 15-mg group who had achieved at least a 75% reduction from baseline 2 weeks after the last dose, 74% maintained at least a 50% reduction in PASI during the 12-week follow-up period. Of patients in the 15-mg group who achieved between a 50% and 75% PASI reduction, 79% maintained at least a 25% reduction in PASI from baseline during the 12-week follow-up period [282].



CLINICAL USE IN DERMATOLOGY
Alefacept is indicated for the treatment of adult patients with moderate to severe plaque-type psoriasis (∼1.5 million in the United States) [288] who are candidates for systemic therapy or phototherapy. Patients who have comorbidities, such as liver and renal disease, for whom systemic immunosuppressive therapies are not options, represent an additional potential patient population that can benefit from biologic therapies like alefacept. As mentioned previously, alefacept is considered to be a remittive therapy that allows patients to enjoy long periods of treatment-free, disease-free living. It is therefore advantageous for the patient who needs a reprieve from chronic therapy.

Unlike most biologic agents that require the patient to self-inject subcutaneously, alefacept is a physician-administered intramuscular injection. This mode of administration represents a clear advantage for patients who, for either psychologic or physical reasons, are not able to self-inject.



USAGE GUIDELINES
Alefacept is contraindicated in patients with a known hypersensitivity to the drug or any of its components [269]. Alefacept has not been formally studied in women who are pregnant or nursing. It is not known whether alefacept is excreted in human milk. The drug has been labeled pregnancy category B and should therefore only be used during pregnancy when clinically necessary. Reproductive toxicology studies were performed in cynomolgus monkeys with alefacept in doses of up to 5 mg/kg per week (∼62 times the human dose based on body weight) and revealed no evidence of impaired fertility or harm to the fetus. Weekly IV bolus injections of alefacept administered to cynomolgus monkeys from organogenesis to gestation did not cause abortifacient or teratogenic effects [269]. Caution should be used when treating elderly individuals because of the higher incidence of infections and malignancies in this population. Alefacept is not indicated for the treatment of pediatric patients.



DRUG INTERACTIONS
No formal interaction studies have been performed [269].



DOSAGE AND MONITORING
Alefacept is approved by the FDA as a single 15-mg intramuscular dose given weekly for 12 weeks. The IV formulation is no longer available. After a 12-week rest period off the drug, patients can be treated with a second 12-week course. The drug is supplied as a sterile, preservative-free, lyophilized powder to be reconstituted with 0.6 mL of sterile water before injection. Monitoring guidelines are presented in Table 4.


Table 4 . Monitoring guidelines for use of immunobiologic agents Drug Monitoring tests Frequency Guidelines for dosage modification
Alefacept CBC and platelets, including total lymphocytes and CD4+ T-cell counts (both must be within normal limits to begin therapy) Baseline Hold therapy if CD4+ T-lymphocyte counts are below < 250 cells/μL
CD4+ T-cell counts Weekly Discontinue drug if CD4+ counts remain below 250 cells/μL for 1 mo
Efalizumab Platelet counts Baseline and once per month for the initial 3-mo treatment period; periodic testing should be done throughout the treatment period Discontinue if thrombocytopenia develops
Etanercept None required — —
Infliximab Tuberculin skin test Baseline —


EFALIZUMAB


PHARMACOLOGY/MECHANISM OF ACTION
Efalizumab is administered as a weekly subcutaneous (SC) injection. Patients (n = 26) with moderate to severe plaque psoriasis who received a starting (SC) dose of 0.7 mg/kg followed by 11 weekly SC doses of 1 mg/kg per week reached steady-state serum concentrations at 4 weeks, with a mean trough concentration of approximately 9 μg/mL. The mean steady-state clearance was 24 mL/kg per day (range, 5–76 mL/kg/d; n = 25). After the last steady-state dose, the mean elimination time of efalizumab was 25 days (range, 13–35 d; n = 17). Mean efalizumab SC bioavailability was estimated to be 50%. Body weight was found to be the most significant covariate affecting clearance of the drug. Patients who received weekly SC doses of 1 mg/kg of efalizumab had similar exposure across body weight quartiles [289].

Efalizumab is a humanized monoclonal antibody directed against CDlla, the α subunit of LFA-1. This binding reversibly blocks the interaction between LFA-1 and intracellular adhesion molecule 1 (ICAM-1). LFA-1 expression is increased on memory T cells, and ICAM-1 is expressed on vascular endothelial cells at sites of inflammation and on keratinoctyes in various T-cell–mediated disorders [290], [291], [292], [293]. Thus, the mechanism of efalizumab prevents the binding of T cells to endothelial cells and blocks T-cell movement into the skin without depleting memory effector T lymphocytes.



ADVERSE EFFECTS


ONCOGENIC POTENTIAL
Of 2762 patients who received efalizumab at various doses for a median duration of 8 months [289], 31 patients were diagnosed with 37 malignancies. Efalizumab-treated patients had a 1.8 per 100 patient-years incidence of malignancies compared with 1.6 per 100 patient-years in placebo-treated patients. Most malignancies were nonmelanoma skin cancers. The incidence of noncutaneous solid tumors and malignant melanoma were within the range that would be expected in the general, non–efalizumab-treated population. Efalizumab, like alefacept, is a novel immunosuppressive agent without long-term safety and efficacy data. Therefore, the role of efalizumab in the long-term development of malignancies will require longer follow-up before any role in the development of malignancy can be excluded.



INFECTIONS
In a pivotal phase 3 multicenter, randomized, placebo-controlled, double-blind study [294] that evaluated the efficacy and safety of efalizumab in dosages of 1 or 2 mg/kg per week, subjects (N = 597) were treated with efalizumab for a maximum of 24 weeks with no increased rate of infection observed among efalizumab-treated patients [294]. The package insert for efalizumab states that the overall incidence of hospitalization for infections was 1.6 per 100 patient-years for efalizumab-treated patients compared with 1.2 per 100 patient-years for placebo-treated patients [289].



EFFECTS ON THE IMMUNE SYSTEM
In the previously described large-scale phase 3 study of 597 patients, 5% of the subjects who were treated with efalizumab developed antiefalizumab antibodies [294]. These effects were not believed to be clinically significant.



THROMBOCYTOPENIA
During clinical trials, thrombocytopenia, as defined as platelet counts at or below 52,000 cells per μL, was observed in eight (0.3%) of efalizumab-treated patients and no placebo-treated patients [289]. Five of the eight patients were treated with systemic steroids. The thrombocytopenia resolved in seven of the eight patients (the eighth patient was lost to follow-up).



MISCELLANEOUS
First-dose reactions are sometimes associated with the administration of monoclonal antibodies. An analysis of the pooled adverse events from the efficacy and safety data for 1095 patients who were treated with efalizumab showed a higher incidence of acute adverse events (defined as headache, chills, fever, nausea, vomiting, or myalgia that occurred on the day of injection or 2 days post injection) than placebo controls (43% versus 27%) [295]. These events were generally mild to moderate in severity and tended to occur after the initial injection, and decreased with each subsequent injection. By the third dose, the incidence of acute adverse events was similar to the placebo-treated group.



SUMMARY OF EFFICACY DATA FROM IMPORTANT CLINICAL TRIALS
Data on efalizumab pooled from two phase 3 clinical trials from 1095 patients with moderate to severe psoriasis showed an improvement of 75% or greater in PASI relative to baseline on day 84 in 29.2% of patients who received efalizumab in dosages of 1.0 mg/kg per week and in 27.6% of patients who received dosages of 2.0 mg/kg per week compared with 3.4% of placebo-treated patients [296]. Of patients who achieved an improvement of 50% or more in PASI, 55.6% had been treated with efalizumab in dosages of 1.0 mg/kg per week and 54.5% had been treated with efalizumab in dosages of 2.0 mg/kg per week compared with 15.1% of patients who were treated with placebo. An extended treatment trial (ACD2059g) was conducted in responders (≥75% PASI improvement from baseline) and partial responders (≥50% PASI improvement from baseline) to examine the effects of continued treatment with the same weekly dosing schedule versus a potentially more convenient every-other-week dosing schedule versus discontinuation of therapy to assess time to relapse. Results showed that every-other-week dosing was sufficient to maintain an improvement of 75% or more in PASI in responders, but weekly dosing resulted in a better clinical response rate among partial responders. After cessation of therapy, psoriasis relapsed at a loss of 50% of the original PASI improvement, with a median time to relapse of 60 to 80 days [295]. Of note, the patients who “rebounded” were discontinued from efalizumab therapy abruptly, without taper or transition to other therapeutic modalities. Currently, there are several ongoing phase 3 trials designed to establish more optimal strategies for cessation of efalizumab therapy, to determine optimal dosing schedules, and to further support efalizumab as a potential long-term therapy.



CLINICAL USE IN DERMATOLOGY
Efalizumab was FDA-approved in October 2003 for the treatment of chronic moderate to severe plaque psoriasis. Efalizumab can be compared favorably with the current systemic antipsoriasis agents in that it is associated with rapid onset and continued clinical improvement in patients with moderate to severe plaque-type psoriasis. It is also similar in that on cessation of therapy, some patients in clinical trials have shown relapse or exacerbation of disease. Of 2589 clinical trial patients treated with efalizumab, 19 (0.7%) experienced worsening of their psoriasis (n = 5) or worsening past baseline after discontinuation of efalizumab (n = 14) [289]. Some of these patients developed pustular or erythrodermic psoriasis. In comparison to systemic immunosuppressive agents, however, efalizumab's mechanism of action is highly specific, and clinical trial data have shown its potential role as a safe and effective long-term therapy without the dose-limiting side effects of the systemic agents. To date, although the long-term safety and efficacy data supporting efalizumab as a chronic therapy have not been established, the favorable side-effect profile and the convenience of a weekly self-administered SC injection make the long-term administration of efalizumab feasible. Trials are currently being conducted to evaluate efalizumab as a potential therapeutic agent for chronic psoriasis.



USAGE GUIDELINES
Efalizumab is contraindicated in patients with a known hypersensitivity to the drug or any of its components. No reproductive toxicity studies have been conducted in pregnant women. Efalizumab has been labeled pregnancy category C. It is not known whether efalizumab is excreted in human milk. The drug should not be used in pregnancy unless the clinical benefits clearly outweigh the risks.

In a developmental toxicity study that used antimouse CD11a antibody at up to 30 times the recommended clinical dose of efalizumab, there was no evidence of maternal toxicity, embryotoxicity, or teratogenicity observed during organogenesis [289].

Caution should be used when treating elderly individuals because of the higher incidence of infections and malignancies in this population. Efalizumab has not been studied in pediatric patients.



DRUG INTERACTIONS
Drug interaction studies have not been performed. Efalizumab should not be used concomitantly with other immunosuppressive agents [289].



DOSAGE AND MONITORING
Efalizumab is administered as a single 0.7-mg/kg, SC conditioning dose followed by a weekly SC dosage of 1 mg/kg. The maximum dosage should not exceed 200 mg weekly [289]. The drug is supplied as a lyophilized, sterile powder to be reconstituted with 1.3 mL of sterile water before injection. Monitoring guidelines are presented in Table 2.



ETANERCEPT


PHARMACOLOGY/MECHANISM OF ACTION
Etanercept is a dimeric fusion protein that competitively inhibits the action of TNF-α, rendering it biologically inactive. Etanercept is created with two identical p75 TNF-α receptor peptides fused to the Fc region of IgG1 [297]. It is this dimeric property of the drug that enables it to bind to two receptors on TNF-α with greater affinity than natural monomeric receptors [298].

TNF-α is produced by type 1 helper T cells within psoriatic plaques. TNF-α has an integral role in the amplification and maintenance of the inflammatory cascade within psoriatic plaques by stimulating the production of chemokines and the expression of adhesion molecules by keratinocytes and vascular endothelial cells [299]. The importance of TNF-α in the inflammatory process has been demonstrated by showing that levels of TNF-α in the serum [300] and blister fluids [301] of involved psoriatic skin are higher than in those of controlled nonpsoriatic skin. In addition, TNF-α levels have been significantly correlated with PASI scores, and decreased levels are associated with clinical improvement after treatment [300].

Pharmacokinetic studies of 25 patients with RA showed that administration of 25 mg of etanercept by a single SC injection resulted in a mean (± standard deviation) half-life of 102 (±30) hours with a clearance of 160 (±80) mL per hour [302]. Pharmacokinetic studies have not been conducted to study the effects of renal or hepatic impairment in patients taking etanercept.



ADVERSE EFFECTS


ONCOGENIC POTENTIAL
The incidence of malignancies in the etanercept-treated population is best evaluated using data from RA studies because these studies represent the longest experience available and published phase 3 data evaluating etanercept in psoriasis clinical trials are currently limited. Moreland et al [303] examined the safety of etanercept therapy in a population of 1272 patients with RA 5 years after they had been treated and found the incidence of malignancies to be 35 in the treatment group. This number was what would be expected according to the National Cancer Institute, Surveillance, Epidemiology, and End Results database.



INFECTIONS
Similar to data on oncogenic potential, data concerning the incidence of infections are also best gleaned from RA studies that have longer clinical experience with the drug. Safety data from 5 years of clinical experience with etanercept therapy in a population of 1272 patients with RA showed the frequency of infections requiring hospitalization or IV antibiotics to be 0.04 per patient-year in the total population [303]. This rate was the same as the rate in the control group.

More recent short-term data from placebo-controlled trials investigating etanercept for the treatment of psoriasis also have examined rates of infection. In a double-blind, placebo-controlled 24-week study that examined the safety and efficacy of etanercept as monotherapy in 672 patients with moderate to severe psoriasis, rates of infection were similar across all treatment groups [304]. The study reported that 11% of placebo-treated patients, 10% of low-dose (25-mg 1×/wk) etanercept-treated patients, 9% of medium-dose (25-mg 2×/wk) etanercept-treated patients, and 5% of high-dose (50-mg 2×/wk) etanercept-treated patients developed an upper respiratory tract infection during the first 12 weeks of therapy. There were no cases of opportunistic infections or tuberculosis (TB) reported during the study. Similarly, in a randomized, double-blind, placebo-controlled 12-week study [305] that looked at the efficacy and safety of etanercept in dosages of 25 mg twice weekly, versus placebo in 60 patients with psoriasis and psoriatic arthritis, the safety profile of etanercept-treated patients was similar to the profiles previously reported in the RA population [306], [307]. Upper respiratory tract infections were one of the most common adverse events, but no adverse event occurred in a significantly greater proportion in the treatment group relative to the placebo group.

Postmarketing reports have reported serious infections and sepsis, including fatalities, associated with the use of etanercept. Many of these serious infections occurred in patients using concomitant immunosuppressive therapy [302]. Usage guidelines concerning infections are discussed in the “Usage guidelines” section.

The reactivation of latent TB has been observed in patients treated with etanercept and infliximab, the other biologic agent that targets TNF. TB also has been reported in much lower numbers in etanercept-treated patients. Thirteen patients (eight in the United States and five in Europe) of approximately 102,000 patients with RA developed TB [299]. The etanercept-related cases occurred sporadically and later during the course of therapy than the infliximab cases. Currently, TB screening is required by the FDA before starting infliximab but not before the initiation of therapy with etanercept. Some experts believe that testing should be done before the initiation of etanercept as well.



EFFECTS ON THE IMMUNE SYSTEM
Data from clinical trials showed that 11% of etanercept-treated patients developed a new positive antinuclear antibody (ANA) titer of 1:40 or greater compared with 5% of placebo-treated patients [299]. Anti-dsDNA antibodies occurred in 15% of etanercept-treated patients compared with 4% of placebo-treated patients [299]. In addition, cases of drug-induced systemic lupus and subacute cutaneous lupus have been reported [308], [309]. These conditions resolved after therapy with etanercept was discontinued, and in one case after corticosteroid treatment was initiated without withdrawal of etanercept therapy [308]. Full cases of systemic lupus erythematosus associated with etanercept therapy are rare [310].



DEMYELINATING DISEASE
In a review of the Adverse Events Reporting System of the FDA, Mohan et al [311] identified 19 patients who developed neurologic symptoms, 17 following etanercept therapy and 2 following infliximab therapy. The neurologic symptoms were in most cases associated with demyelinating lesions of the CNS and were all temporally related to anti–TNF-α therapy. Symptoms improved in all patients after discontinuation of anti–TNF- α therapy. One patient's symptoms returned on rechallenge with etanercept. It is important to note that 4 of the 19 patients had a prior history of MS or MS-like symptoms. The authors suggested avoiding anti-TNF-α therapy in patients with MS or in patients with a family history of MS. An outline of the clinical approach to patients receiving anti–TNF-α therapy who develop new neurologic signs suggestive of demyelination is also provided in this study [311].



INJECTION SITE REACTIONS
In controlled clinical trials, injection site reactions were the only adverse event that occurred significantly more often in etanercept-treated patients than in placebo-treated patients. Approximately between 42% and 49% of etanercept-treated patients in controlled clinical trials experienced injection site reactions [306], [307]. In a study that retrospectively reviewed medical records of patients who had received etanercept injections and who were still being actively treated with etanercept, 21 (20%) of 103 patients reported injection site reactions [312]. The reactions occurred within the first months of therapy, within 1 to 2 days of injecting, and resolved within a few days. The lower incidence of injection site reactions found in this study compared with the 42% to 49% incidence in controlled clinical trials was attributed to the retrospective nature of the study. The authors of this study performed a histologic and immunophenotypic analysis of skin biopsy specimens and concluded that the reactions may be an example of a T-lymphocyte–mediated delayed-type hypersensitivity reaction. Injection site reactions can be treated with cool compresses and 1% hydrocortisone ointment. Rotating sites of injection is also recommended.



SUMMARY OF EFFICACY DATA FROM IMPORTANT CLINICAL TRIALS
Several clinical trials have investigated etanercept as monotherapy for the treatment of psoriasis. A 24-week phase 2, multicenter, double-blind, placebo-controlled trial of 112 patients with chronic moderate to severe plaque-type psoriasis who were treated with etanercept in SC dosages of 25 mg twice weekly found that, at week 12, 30% of etanercept-treated patients achieved at least a 75% improvement in PASI, compared with 2% of placebo-treated patients (P < 0.001) [313]. By week 24, 56% of etanercept-treated patients and 5% of placebo-treated patients achieved an improvement of 75% or greater in PASI (P < 0.001).

A phase 3, placebo-controlled, double-blind, parallel-group study assessed the safety and efficacy of a 24-week course of etanercept in SC dosages of 25 mg once weekly (low dose), 25 mg twice weekly (medium dose), 50 mg twice weekly (high dose), or placebo in 672 patients with moderate to severe plaque-type psoriasis [304]. At week 12, 14%, 34%, 49%, and 4% of the patients in the low, medium, high, and placebo groups, respectively, achieved a PASI improvement of at least 75% (P < 0.001 for all three comparisons with the placebo group). As early as week 2 of the study, the mean percentages of PASI improvements were statistically significant for all three etanercept-treatment groups compared with baseline. At week 12, mean levels of improvement were 40.9%, 52.6%, 64.2%, and 14% in the low-dose, medium-dose, high-dose, and placebo groups, respectively. Results at week 24 showed an improvement of 75% or greater in 25%, 44%, and 59% of the patients in the low-, medium-, and high-dose groups, respectively. There was no placebo comparison group at this point in the study.



CLINICAL USE IN DERMATOLOGY
Etanercept has more than 130,000 patient-years of treatment experience (mostly in the RA population) in both controlled clinical trials and postmarketing experience [299]. Etanercept was FDA-approved in April 2004 for the treatment of adult patients with chronic moderate to severe plaque-type psoriasis. Etanercept was previously granted FDA approval for the treatment of psoriatic arthritis. It is also indicated for reducing signs and symptoms of moderate to severe active polyarticular-course juvenile RA. Because between 5% and 42% of patients with psoriasis also have concomitant psoriatic arthritis [314], etanercept represents an ideal biologic agent in physicians' current armamentarium for the treatment of both of these disorders. In addition, similar to efalizumab, etanercept can be administered with methotrexate, a benefit that has numerous favorable clinical implications when treating patients with psoriasis or psoriatic arthritis. Like other SC self-administered biologics, etanercept can be administered by the patient at home, a feature that offers tremendous patient independence. Unlike many biologics, etanercept requires no laboratory monitoring during treatment. Data extrapolated from RA studies suggest that etanercept therapy may (similar to efalizumab) have a role as a therapeutic agent in chronic conditions administered on a long-term continuous basis.

Etanercept has been reported to be clinically effective in several other cutaneous disorders, including the following: scleroderma [315]; cicatricial pemphigoid [316]; in a patient with common variable immunodeficiency who presented with scarring alopecia, arthritis, diarrhea, and recurrent infections [317]; and for recurrent apthous stomatitis [318].



USAGE GUIDELINES
Etanercept is contraindicated in patients with a known hypersensitivity to the drug or any of its components and should not be administered to patients with sepsis. Treatment with etanercept should not be initiated in patients with active or chronic localized infections. The manufacturer of etanercept cautions that the drug should not be administered to patients who develop serious infections or sepsis and caution should be taken when considering treating patients with conditions that may predispose to infections, such as poorly controlled or advanced diabetes. Caution should also be exercised when considering using etanercept in patients with pre-existing or recent-onset CNS demyelinating disorders [302].

Developmental toxicity studies of etanercept performed in rats and rabbits in doses between 60- to 100-fold higher than the human dose have not resulted in harm to the fetus [303]. Whether etanercept can impair fertility in humans is unknown. The drug should not be used during pregnancy unless the clinical benefits clearly outweigh the risks. Etanercept has been labeled as pregnancy category B. It is not known whether etanercept is excreted in human milk. Caution should be used when treating elderly individuals because of the higher incidence of infections and malignancies in this population. Etanercept is indicated for the treatment of polyarticular-course juvenile RA, but it has not been studied in children younger than 4 years [302].



DRUG INTERACTIONS
No formal interaction studies have been performed. In a study of patients with RA who were treated with etanercept and anakinra therapy for up to 24 weeks, however, the rate of serious infections was 7% in the dual-treatment group compared with 0% in those with etanercept alone [302].



DOSAGE AND MONITORING
Etanercept is indicated for adult patients with moderate to severe plaque-type psoriasis as a step-down dosing regimen of 50 mg administered twice weekly for 3 months, followed by a 50-mg weekly maintenance dose. Etanercept is also indicated for adults with psoriatic arthritis or RA as a 25-mg twice-weekly SC injection administered 72 to 96 hours apart [302]. The drug is supplied as a sterile, preservative-free, lyophilized powder to be reconstituted with 1 mL of bacteriostatic water before injection. Monitoring guidelines are presented in Table 4.



INFLIXIMAB


PHARMACOLOGY/MECHANISM OF ACTION
Pharmacokinetic study data from 17 patients with moderate to severe psoriasis treated with either 5 mg/kg or 10 mg/kg doses of infliximab showed maximum infliximab concentrations at day 14 [319]. For the 5- and 10-mg/kg–dose groups, the concentrations were 158.14 mg/mL and 298.89 mg/mL, respectively—concentrations that were directly proportional to the administered doses. The median elimination half-life for infliximab was 7.62 (interquartile range, 6.62–10.15) and 9.97(interquartile range, 6.17–10.1432) days for the 5 mg/kg and 10 mg/kg doses, respectively. The half-life and maximum infliximab concentrations in the 10-mg/kg psoriasis group were similar to those seen in patients with Crohn's disease who were treated with 5 mg/kg of infliximab.

Infliximab is a monoclonal antibody that targets TNF-α. It is composed of a human constant region and a murine variable region, factors that make infliximab chimeric in nature. By binding to both soluble and transmembrane forms of TNF-α, infliximab can trigger complement-mediated lysis of cells expressing TNF- α [320]. As previously described, TNF-α is an important inflammatory cytokine to target because it is central to the pathogenesis of psoriasis. TNF-α fuels the synthesis of many key cytokines involved in the inflammatory cascade, such as IL-1, IL-6, and IL-8, and stimulates Langerhans' cell maturation and migration from the skin to lymph nodes [321]. TNF-α activates nuclear factor κB, a transcription factor that is central to the inflammatory process leading to psoriasis [322]. TNF-α also has been shown to increase keratinocyte proliferation in vitro [319]. In addition, both psoriatic lesional skin and the plasma of patients with psoriasis have shown increased levels of TNF-α [323].



ADVERSE EFFECTS


ONCOGENIC POTENTIAL
The long-term risks of development of infliximab-associated malignancies remain unknown. Nahar et al's [324] review of the use of infliximab for the treatment of Crohn's disease and RA reported that 18 of 1372 infliximab-treated patients developed 19 new or recurrent malignancies over 1430 patient-years of follow-up [324]. The authors concluded that it could not be determined whether these malignancies were induced by infliximab treatment. There are several factors that complicate the ability to determine whether the reported occurrences of lymphoma and other malignancies are related to infliximab treatment. Although controversial, rates of lymphoproliferative disease have been shown to be higher among RA, Crohn's disease, and psoriasis populations [325], [326], [327], [328], [329], [330], [331], [332], [333]. In addition, lymphoproliferative disorders tend to occur at an increased rate in patients who are immunosuppressed [332], [333]. Many patients who have chronic inflammatory diseases, such as RA, Crohn's disease, or psoriasis, have long exposure histories to immunosuppressive agents, complicating the ability to analyze the potential causal relationship even further. Last, because Epstein-Barr virus is a well-known cause of lymphoma in organ transplant patients [334], [335], the virus may also have an integral role in the development of malignancies in patient populations where immunosuppressive agents are commonly used.



INFECTIONS
Infections, and especially reactivation of TB, have been a major issue of concern associated with the use of infliximab. Keane et al [336] performed an analysis of all reports as of May 29, 2001, of TB cases that occurred after infliximab therapy through the FDA's MedWatch system. Details of this system are available at http://www.fda.gov/cder/aers/. At the time of the analysis, approximately 147,000 patients worldwide had received infliximab. The analysis showed 70 reported cases of TB that occurred after treatment with infliximab for a median of 12 weeks. TB developed in 48 of the patients after three or fewer infusions of infliximab. Of the 70 cases, 40 were extrapulmonary disease. Most cases (64) occurred in countries with a low incidence of TB. The reported frequency of TB associated with infliximab therapy was much higher than the reported frequency of other opportunistic infections. Several cases of histoplasmosis also have been reported, however. Although the authors were not able to completely assess the TB status of the patients pretreated with infliximab, they concluded that the TB was likely reactivation TB.

As mentioned previously, histoplasmosis is another potentially life-threatening infection that has been reported to the FDA as a possible complication associated with infliximab therapy. In a review of the FDA's passive surveillance database for monitoring postlicensure adverse events, Lee et al [337] identified all cases of histoplasmosis received through July 2001 in patients who had been treated with either infliximab or etanercept, the two licensed anti–TNF-α biologic agents. Ten cases of Histoplasma capsulatum (HC) infection were reported. Nine of these cases were associated with infliximab therapy, and one case was associated with etanercept therapy. Clinical manifestations of histoplasmosis, including fever, malaise, cough, dyspnea, and interstitial pneumonitis, occurred within 1 week to 6 months of the first dose. It is important to note that all of the patients had been treated with concomitant immunosuppressive agents during infliximab therapy, and all of the patients resided in HC-endemic areas. A detailed discussion of the clinical implications of the association of infliximab with reactivation TB and histoplasmosis will be addressed in the “Usage guidelines” section.

In a review of the published literature and presentations at scientific meetings from a search of Medline and pre-Medline English-language articles published from 1966 to June 2002 of infliximab for the treatment of RA and Crohn's disease, Nahar et al [324] found that treated infections were reported in 36% of patients receiving infliximab compared with 26% of placebo-treated patients. Respiratory and urinary tract infections were the most frequently reported type of infection. In addition, several serious infections were reported, including pneumonia, abscess, cellulites, skin ulceration, pyelonephritis, sepsis, two cases of TB, and one case of disseminated coccidioidomycosis. The authors pointed out that most of the patients were on concomitant immunosuppressive therapies in two of the large clinical trials in the review, A Crohn's Disease Clinical Trial Evaluating Infliximab in a New Long-Term Treatment Regimen (ACCENT) [338] and Anti-TNF Trial in Rheumatoid Arthritis with Concomitant Therapy (ATTRACT) [339].

Chaudhari et al [340] assessed the clinical benefit and safety of infliximab for the treatment of moderate to severe plaque psoriasis in a double-blind randomized trial of 33 patients. In contrast to the aforementioned data from the literature, the investigators did not observe any serious adverse events during the 10-week study period where patients were randomized to receive 5 mg/kg, 10 mg/kg, or placebo in a 1:1:1 ratio. Patients enrolled in the study did not use any other treatments for their psoriasis during the study and had stopped taking systemic therapy (including cyclosporine, methotrexate, acitretin, and UVB and PUVA) at least 4 weeks before the first dose of study medication. Therefore, unlike many of the patients in previous clinical trials who were receiving concomitant immunosuppressive agents, the patients in this trial were not, a factor that may explain the lack of serious adverse event occurrences. In addition, all patients had a clear chest radiograph within 1 month of receiving the first dose of the study medication.



EFFECTS ON THE IMMUNE SYSTEM
In the review of the literature of patients with RA and Crohn's disease treated with infliximab, Nahar et al [324] found that approximately 10% of all patients in clinical trials developed antibodies to infliximab. The development of antibodies to the drug was associated with an increased likelihood of developing infusion reactions. Approximately 44% of patients with Crohn's disease treated with infliximab developed ANAs between screening and the last clinical evaluation [324].

In the ATTRACT study [339], a multicenter, randomized, double-blind, placebo-controlled phase 3 trial, 428 patients with active RA were treated with continuous methotrexate and randomized to one of four infliximab treatment regimens. Of 342 exposed patients, 16% (54) developed anti-dsDNA antibodies using the Farr assay of 10 units/mL compared with 0% of placebo-treated patients. Of the 54 patients, 15 (4%) had titers greater than 25 units/mL.



INFUSION REACTIONS
Infusion reactions, defined as any adverse event occurring during an infusion or within 1 to 2 hours after an infusion, occurred in approximately 20% of infliximab-treated patients compared with 10% of placebo-treated patients in clinical trials [341]. Less than 1% were considered serious reactions characterized by clinical symptoms of anaphylaxis, convulsions, erythematous rash, or hypotension. Of the patients who experienced infusion reactions, approximately 3% discontinued infliximab therapy because of the reactions. Infusion reactions can be avoided by slowing down the infusion, premedicating with antihistamines, and, in some cases, administering systemic corticosteroids [310]. It is therefore recommended that medications such as antihistamines, corticosteroids, and epinephrine be available at the infusion site.

There have been reports of patients experiencing delayed infusion reactions in instances where infliximab was restarted [324]. In a study in which 37 of 41 patients with Crohn's disease were retreated after a 2- to 4-year lapse between treatments, 10 of the patients experienced adverse events that occurred 3 to 12 days following the infusion. Clinical signs and symptoms included myalgia or arthralgia, with fever or rash, pruritus, edema of the face, hand, or lip, dysphagia, urticaria, sore throat, and headache. None of the patients had experienced an infusion-related adverse event previously. Approximately 39% (9 of 23) of the patients had received a liquid formulation, which is no longer available, and 7% (1 of 14) had received the lyophilized formulation. The makers of the drug do not know if occurrences of these reactions were caused by differences in formulation [341].



CONGESTIVE HEART FAILURE
Infliximab has been associated with adverse outcomes in patients with congestive heart failure. In a randomized study of 150 patients with stable New York Heart Association class 3 or 4 heart failure and left ventricular ejection fraction of 35% or less, patients were randomized to receive either placebo (n = 49), infliximab doses of 5 mg/kg (n = 50), or infliximab doses of 10 mg/kg (n = 51) [342]. The results suggested that infliximab therapy over a 6-week period was associated with an increased risk of worsening heart failure in patients in the high-dose (10 mg/kg) group. The authors concluded that although a similar risk was not observed in the low-dose (5 mg/kg) group, longer term treatment with infliximab at this dose could result in more severe adverse events.

Postmarketing reports of worsening heart failure in patients being treated with infliximab have been reported. These reports have occurred in patients with and without precipitating factors. In addition, there have been rare postmarketing reports of new-onset heart failure in patients without diagnosed cardiac disease. There is a detailed discussion of the clinical implications of treating patients who have heart failure with infliximab in the “Usage guidelines” section.



DEMYELINATING DISEASE
As mentioned previously, neurologic symptoms associated with demyelination of the CNS have been reported to be associated with the anti–TNF-α therapies.



SUMMARY OF EFFICACY DATA FROM IMPORTANT CLINICAL TRIALS
The first case documenting the efficacy of infliximab for the treatment of psoriasis was described in a case report of a patient with Crohn's disease and severe psoriasis who was treated with a single 5-mg/kg infusion of infliximab and achieved an improvement in PASI of 22 points within 4 weeks [343]. Subsequent to that case, several reports have attested to the efficacy of infliximab for the treatment of moderate to severe psoriasis [344], [345].

A small-scale study was conducted to garner information about the efficacy of infliximab for the treatment of psoriasis in patients with concomitant psoriatic arthritis [346]. Six patients with psoriasis and psoriatic arthritis unresponsive to methotrexate therapy were treated with 5-mg/kg doses of infliximab at weeks 0, 2, and 6, and PASI evaluations were performed at baseline and 10 weeks after therapy started. At week 10, all six patients achieved improvement in psoriasis as measured by PASI score.

In a randomized, double-blind, placebo-controlled clinical trial designed to assess the clinical benefit and safety of infliximab as monotherapy for patients with moderate to severe psoriasis, 33 patients were assigned to receive placebo (n = 11), infliximab doses of 5 mg/kg (n = 11), or infliximab doses of 10 mg/kg (n = 11) at weeks 0, 2, and 6 [340]. Assessments were performed at week 10 using the PGA as the primary endpoint and the PASI score as the secondary endpoint. Nine of 11 (82%) of patients in the 5-mg/kg treatment group and 10 of 11 (91%) of patients in the 10-mg/kg group achieved the primary endpoint on the PGA at week 10 of good, excellent, or clear. This finding was in comparison to 11 (18%) of patients in the placebo group. The difference between infliximab doses of 5 mg/kg and placebo was 64% (95% confidence interval [CI], 20–89; P = 0.0089). The difference between infliximab doses of 10 mg/kg and placebo was 73% (CI, 30–94; P = 0.0019). Data regarding the secondary endpoint of the study, change in PASI score, were also significant. Nine of 11 (82%) of patients in the 5-mg/kg group and 8 of 11 (73%) of patients in the 10-mg/kg group showed an improvement of 75% or more in PASI score compared with 11 (18%) patients in the placebo group. The difference between infliximab doses of 5 mg/kg and placebo was 64% (CI, 20–90; P = 0.0089); and the difference between infliximab doses of 10 mg/kg and placebo was 55% (CI, 9–85; P = 0.03). The mean percentage improvements in PASI scores were significantly higher among the infliximab-treated patients as early as week 2 of therapy (P < 0.0003). The median time to response in both treatment arms was 4 weeks.



CLINICAL USE IN DERMATOLOGY
Infliximab is currently approved for treatment of RA and Crohn's disease and has been reported to have clinical efficacy in several cutaneous disorders, including the following: psoriasis [340], [344], [345], [346]; psoriatic arthritis [346]; pustular psoriasis [347]; hidradenitis suppurativa [348]; pyoderma gangrenosum [344], [349], [350], [351], [352]; Behçet's syndrome [353], [354], [355]; synovitis, acne, pustulosis, hyperostosis, and osteitis, or SAPHO, syndrome [356]; subcorneal pustular dermatosis [357]; and toxic epidermal necrolysis [358]. Similar to the clinical response to cyclosporine, high percentages of patients respond to infliximab, and response rates tend to be rapid. Unlike cyclosporine therapy, however, infliximab is not associated with the concerning cumulative dose-related side effects of decreased renal function and hypertension. Another advantage of infliximab is that, similar to efalizumab and etanercept, infliximab has shown clinical efficacy for both psoriasis and psoriatic arthritis, although it is not yet FDA-approved for either indication. In addition, psoriasis is more prevalent in patients who have inflammatory bowel disease [359]. Infliximab therapy could be beneficial therefore for patients with concomitant inflammatory bowel disease and psoriasis. Although both etanercept and infliximab inhibit TNF-α, infliximab has shown superior clinical efficacy for the treatment of psoriasis. Chaudhari et al [340] offered some explanations for this discrepancy. They asserted that differences may be from the route of administration (IV for infliximab versus SC for etanercept), differences in the patient populations in clinical trials, or differences in the mechanism by which the drugs work. The different mechanisms have been shown by in vitro data, which have shown that, unlike etanercept, infliximab is able to trigger complement-mediated lysis of TNF-α–expressing cells [320]. If this mechanism is accurate, then the implications are that inflximab is able to abolish activated T cells and antigen-presenting cells, a potential explanation for the rapidity and thoroughness of the clinical responses observed in trials.



USAGE GUIDELINES
A black box warning has been issued by the manufacturer of infliximab cautioning that the drug should not be given to patients with clinically important active infections. Caution should also be taken when considering the use of infliximab for patients with chronic or recurrent infections. If a patient develops a serious infection while being treated with infliximab, the treatment should be discontinued. TB (frequently disseminated or extrapulmonary at clinical presentation), invasive fungal infections, and other opportunistic infections have been observed in patients being treated with infliximab [341]. Some infections have been fatal. Patients should be evaluated for latent TB infection with a tuberculin skin test, and treatment of latent TB infections should be started before infliximab therapy. For patients who have resided in regions where histoplasmosis or coccidioidomycosis is endemic, the benefits and risks of infliximab therapy should be carefully considered before initiation of therapy.

Infliximab should only be used in patients with heart failure after other treatment options have been considered. If a decision is made to administer infliximab to these patients, the patients should be closely monitored during therapy and treatment should be discontinued if new or worsening symptoms of heart failure appear [341].

Physicians should exercise caution when considering the use of infliximab for the treatment of patients with pre-existing or recent-onset CNS demyelinating or seizure disorders [341].

Infliximab should not be administered to patients with known hypersensitivity to any murine proteins or other component of the drug. To date, no animal reproduction studies have been performed. It is therefore advised that infliximab only be used in pregnancy when clearly clinically necessary [341].

Infliximab only cross-reacts with TNF-α in humans and chimpanzees. In a developmental toxicity study using cV1q antimouse TNF-α, an analogous antibody that inhibits mouse TNF-α, no evidence of carcinogenesis, mutagenesis, or impairment of fertility was observed [341]. Doses of up to 40 mg/kg did not produce any adverse effects in animal reproduction studies. It is not known whether infliximab can cause harm to the fetus, if it can affect reproductive capacity, or if it is excreted in human milk or absorbed systemically post ingestion. Infliximab has been labeled pregnancy category B.

Because of the higher incidence of infections in the elderly population, caution should be used when treating elderly patients. Infliximab is currently not indicated for pediatric use.



DRUG INTERACTIONS
Drug interaction studies with infliximab have not been conducted. In RA and Crohn's disease clinical trials, most patients were treated with one or more concomitant medications. Patients with RA were treated with concomitant methotrexate, NSAIDs, folic acid, corticosteroids, or narcotics. Patients with Crohn's disease in clinical trials were treated with concomitant antibiotics, antiviral medications, corticosteroids, 6-MP/azathioprine, and aminosalicylates. Patients with Crohn's disease who received immunosuppresants tended to have fewer infusion reactions. As previously mentioned, Nahar et al [324] reported that concomitant treatment with immunosuppresants may have predisposed patients in the ACCENT [338] and ATTRACT [339] clinical trials to increased rates of serious infections.



DOSAGE AND MONITORING
Infliximab is indicated for the treatment of RA and Crohn's disease. Infliximab is administered as an IV drip over the course of several hours. The mode of administration of infliximab is a potential drawback for both patients and physicians because of the time commitment involved, increased need for skilled health care workers in the office at the time of administration, and potential physical burden for arthritic patients who may have difficulty sitting in one position for the length of the infusion. For the treatment of RA, infliximab is given as a 3-mg/kg IV infusion followed by infusions at weeks 2 and 6, and then every 8 weeks thereafter. Infliximab should be administered in combination with methotrexate for the treatment of RA. Doses of up to 10 mg/kg may be used for patients with RA who have incomplete clinical responses to lower doses. For treatment of patients with Crohn's disease, the recommended dose of infliximab is 5 mg/kg as an induction dose at baseline and weeks 2 and 6. Maintenance doses of 5 mg/kg every 8 weeks after induction can be used to treat moderate to severe active Crohn's disease or fistulizing disease. Doses of up to 10 mg/kg may be used for the treatment of Crohn's disease. For treatment of psoriasis and Crohn's disease, the lower 5-mg/kg dose of infliximab has shown greater efficacy than the 10-mg/kg dose [340], [360].

The drug is supplied as a sterile, white, lyophilized powder for IV infusion. Infliximab vials do not contain preservatives and must therefore be used immediately after reconstitution. Monitoring guidelines are presented in Table 4.



SUMMARY
Azathioprine, cyclophosphamide, methotrexate, cyclosporine, and MMF are the nonsteroidal immunosuppressive agents most commonly used by dermatologists. Azathioprine has a relatively good safety profile and is therefore often preferred for the treatment of chronic eczematous dermatitides and bullous disorders. Awareness of the role of genetic polymorphisms in its metabolism can increase the efficacy and safety of this drug. Cyclophosphamide is an antimetabolite that has a more rapid onset of immunosuppressive effect than azathioprine but has significant short- and long-term toxicity. It is of use in fulminant, life-threatening cutaneous disease. Methotrexate is an antimetabolite that has significant anti-inflammatory activity. Despite its hepatotoxicity, its role in inflammatory dermatoses is broadening. Cyclosporine has potent T-cell inhibitory effects secondary to interference with intracellular signal transduction, and its use in dermatology is rapidly expanding. Given the evidence for cumulative renal toxicity, it currently has a role in the short-term treatment of refractory psoriasis and atopic dermatitis, and in select inflammatory dermatoses. MMF is an immune suppressant with wide potential dermatologic applications, especially for bullous disorders, pyoderma gangrenosum, and psoriasis. It has a mechanism of action similar to azathioprine, and it is generally well tolerated. Although some studies found a slightly higher incidence of lymphoproliferative malignancies, MMF has a better overall safety profile than azathioprine. It is more expensive, however. Both mycophenolate and azathioprine should be used in conjunction with oral corticosteroids because they are “steroid sparing” but not “steroid replacing.” They are usually required when it is impossible to reduce steroids to an acceptably low level. When they are added, as they become effective, the corticosteroid taper is resumed toward the target maintenance dose.

Alefacept, efalizumab, etanercept, and infliximab are the immunobiologic agents currently most commonly used by dermatologists. Alefacept, the first immunobiologic agent to be approved for the treatment of adult patients with moderate to severe plaque-type psoriasis, is a fusion protein that blocks T-cell activation and selectively reduces memory T cells. Because of its unique mechanism of action, alefacept is considered to be the only remittive biologic agent. Therefore, patients who respond effectively to alefacept can enjoy long-lasting therapy-free reprieves for more than 7 months. Alefacept is also safe; safety and tolerability profiles were shown to be similar to placebo in phase 3 clinical trials. Similar to all of the immunobiologic agents, data on the potential for the development of malignancies require longer follow-up periods before a possible role of these agents in the development of malignancy can be excluded. The intramuscular route of administration, and the need for weekly CD4+ T-cell counts, also distinguishes alefacept, because it requires the patient to make weekly visits to a physician's office. Efalizumab, a humanized monoclonal antibody directed against CD11a, is indicated for the treatment of chronic moderate to severe plaque-type psoriasis. Unlike alefacept, efalizumab is administered as a weekly SC injection. Thrombocytopenia was reported in a small percentage of clinical trial patients; therefore, platelet counts must be monitored throughout treatment. Efalizumab is generally well tolerated but, similar to many of the systemic immunomodulators previously discussed, on cessation of therapy, some patients have experienced clinically significant relapse or exacerbation of psoriasis. Although long-term safety data have not been established for any of the immunobiologic agents, efalizumab has been shown to have a favorable side-effect profile and potential as a long-term therapeutic agent for chronic psoriasis. Etanercept is a dimeric fusion protein that inhibits TNF-α. Etanercept is FDA-approved for the treatment of psoriasis, psoriatic arthritis, and RA, and for reducing signs and symptoms of moderate to severe active polyarticular-course juvenile RA. Etanercept has a favorable safety profile. It is the only immunobiologic agent of the four discussed that does not require laboratory monitoring. Infliximab is a chimeric monoclonal antibody that targets TNF-α. It is currently indicated for the treatment of RA and Crohn's disease but has shown efficacy for a wide array of dermatologic conditions, especially psoriasis and psoriatic arthritis, pyoderma gangrenosum, and the cutaneous manifestations of Behçet's syndrome. High percentages of patients with psoriasis respond to infliximab, and response rates tend to be rapid and long-lasting. Infliximab has several potential drawbacks, however, including its route of administration, which is by means of an IV drip over the course of several hours. Infusion reactions also have been a concern, although less than 1% of infusion reactions in clinical trials were considered serious. Other issues have been postmarketing reports of worsening heart failure, reactivation TB, and other opportunistic infections. In addition, some patients have developed neutralizing antibodies. Unlike methotrexate and cyclosporine, for example, infliximab is neither hepatotoxic nor nephrotoxic; it therefore represents a useful therapeutic agent for patients with severe psoriasis who have contraindications to other immunosuppressive agents or who are recalcitrant to other therapies.


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