Efalizumab: continuous therapy for chronic psoriasis

Efalizumab in the Treatment of Psoriasis

Background:

Efalizumab (anti-CD11a), a targeted, reversible T-cell modulator, is a humanized monoclonal antibody that provides a rapid onset of action of clinical benefit and has been studied up to 36 months, showing continuous control of plaque-type psoriasis. Efalizumab has recently been approved in Canada for this indication.

Objective:

To examine the efficacy and safety of efalizumab by presenting the latest data in the treatment of psoriasis.

Methods:

We searched MEDLINE (1966–2005) for randomized, double-blind studies of efalizumab (1 mg/kg for 12 weeks) using the following key words: psoriasis, efalizumab, biologics, and treatment.

Results:

It was found that the proportion of patients who achieved Psoriasis Area and Severity Index (PASI) 75 and PASI 50 ranged from 22 to 39% and 52 to 61%, respectively. PASI 75 improvement was achieved in 44% of patients, who continued to receive efalizumab by week 24. Following 36 months of continuous treatment, a PASI 75 response was achieved by 45% (intent-to-treat [ITT] analysis), 59% (maintenance group analysis), and 73% (as-treated analysis). Its safety profile was similar during the 12-week and 36-month treatment periods.

Conclusions:

Currently, more than 3,500 patients have received efalizumab in clinical trials. Efalizumab may be an important treatment option for dermatologists seeking to provide a well-tolerated and effective treatment modality for patients with moderate to severe chronic plaque psoriasis.

Effective management of psoriasis symptom worsening during efalizumab therapy without discontinuing treatment: A case study

Efalizumab is an effective therapy for the long-term treatment of chronic plaque psoriasis. However, regardless of the type of antipsoriatic treatment a patient is receiving, natural fluctuations in symptom severity occur throughout the course of the disease, and need to be managed appropriately. Here, we report the case of a patient with moderate chronic plaque psoriasis resistant to conventional treatments, who initially showed an excellent response to efalizumab (1 mg/kg per week, subcutaneous injection), but then experienced symptom exacerbation after 8 weeks of treatment. This worsening of symptoms was successfully controlled using a short course of concomitant methotrexate treatment (15 mg/week, intramuscular injection). After 1 month, the clinical signs had cleared, methotrexate treatment was stopped and efalizumab therapy was continued. These results show the effective use of a short course of concomitant methotrexate to control fluctuations in psoriasis severity in a patient receiving efalizumab therapy in general clinical practice.

[Efficacy of short- and long-term efalizumab]

T cells play an important role in the immune system and in the inflammatory response that determines the development and maintenance of psoriasis plaques. Better understanding of the pathophysiology of this disease has led to the development of specific biological treatments aimed at patients with extensive psoriasis. Traditionally, psoriasis has been treated with drugs which, in spite of their efficacy, have a toxicity associated to their long-term use. Thus, they cannot be used safely, comfortably or efficiently in many patients. Efalizumab, a biological agent specifically and selectively directed towards blocking the key steps in the pathogenesis of psoriasis, has been shown to be effective and safe in the short and long term in the treatment of psoriasis in more than 15 phase I, II and III clinical trials. In this article, the results of efficacy at 12 weeks, 6 months and three years are reviewed. Efalizumab arises as an important addition to the dermatological pharmacopoeia for the long-term treatment of psoriasis.

The CD11a Binding Site of Efalizumab in Psoriatic Skin Tissue as Analyzed by Multi-Epitope Ligand Cartography Robot Technology

Efalizumab (Raptiva) is an immunomodulating recombinant humanized IgG1 monoclonal antibody that binds to CD11a, the alpha-subunit of leukocyte function antigen-1 (LFA-1). By blocking the binding of LFA-1 to ICAM-1, efalizumab inhibits the adhesion of leukocytes to other cell types and interferes with the migration of T lymphocytes to sites of inflammation (including psoriatic skin plaques). Analysis of the response in patients treated with efalizumab to date shows that distinct groups of responders and nonresponders to the drug exist. It would therefore be of great practical value to be able to predict which patients are most likely to respond to treatment, by identifying key parameters in the mechanism of action of efalizumab. Detailed investigation and detection of multiple epitopes in microcompartments of skin tissue has until recently been restricted by the available technology. However, the newly developed technique of Multi-Epitope Ligand Cartography (MELC) robot technology combines proteomics and biomathematical tools to visualize protein networks at the cellular and subcellular levels in situ, and to decipher cell functions. The MELC technique, which is outlined in this paper, was used to help characterize the binding of efalizumab to affected and unaffected psoriatic skin as compared to normal control skin under ex vivomodel conditions. Efalizumab was labeled with fluorescein isothiocyanate and integrated into a MELC library of more than 40 antibodies. These antibodies were selected for their potential to detect epitopes which may be indicative of (a) various cell types, (b) structural components of the extracellular matrix, or (c) the processes of cell proliferation, activation and adhesion. Efalizumab bound to CD11a in affected psoriatic skin by a factor 15x and 32x higher than in unaffected psoriatic skin and normal control skin, respectively. CD11a and the efalizumab binding site were primarily expressed in the extravascular dermis, whereas CD54 (ICAM-1) as its ligand was most prevalent in the dermal vessels. T lymphocytes (for which the markers were CD3, CD8, CD4, and CD45R0) were the major cellular targets of efalizumab. In contrast, NK cells were only a minor target of efalizumab. Our study demonstrated that efalizumab represents a treatment for psoriasis that primarily targets memory CD4+ and CD8+ T cells and has a high specificity for psoriatic disease activity. Moreover, we hereby introduce the novel principle of a biological drug-binding biochip assay being especially useful for the future monitoring of psoriatic skin lesions under efalizumab treatment conditions.

Identification and characterization of a human monoclonal antagonistic antibody AL-57 that preferentially binds the high-affinity form of lymphocyte function-associated antigen-1

LFA-1 (alpha(L)beta(2)) mediates cell-cell and cell-extracellular matrix adhesions essential for immune and inflammatory responses. One critical mechanism regulating LFA-1 activity is the conformational change of the ligand-binding alpha(L) I domain from low-affinity (LA), closed form, to the high-affinity (HA), open form. Most known integrin antagonists bind both forms. Antagonists specific for the HA alpha(L) I domain have not been described. Here, we report the identification and characterization of a human antibody AL-57, which binds to the alpha(L) I domain in a HA but not LA conformation. AL-57 was discovered by selection from a human Fab-displaying library using a locked-open HA I domain as target. AL-57 Fab-phage bound HA I domain-expressing K562 cells (HA cells) in a Mg(2+)-dependent manner. AL-57 IgG also bound HA cells and PBMCs, activated by Mg(2+)/EGTA, PMA, or DTT. The binding profile of AL-57 IgG on PBMCs was the same as that of ICAM-1, the main ligand of LFA-1. In contrast, an anti-alpha(L) murine mAb MHM24 did not distinguish between the HA and LA forms. Moreover, AL-57 IgG blocked ICAM-1 binding to HA cells with a potency greater than MHM24. It also inhibited ICAM-1 binding to PBMCs, blocked adhesion of HA cells to keratinocytes, and inhibited PHA-induced lymphocyte proliferation with potencies comparable with MHM24. These results indicate that specifically targeting the HA I domain is sufficient to inhibit LFA-1-mediated, adhesive functions. AL-57 represents a therapeutic candidate for treatment of inflammatory and autoimmune diseases.

Efalizumab-induced autoimmune pancytopenia

Efalizumab is a recombinant, humanized monoclonal anti-CD11a antibody used for the treatment of moderate to severe plaque psoriasis. Immune-mediated thrombocytopenia and anaemia have previously been reported with this therapy. We describe the first case of immune-mediated pancytopenia in a patient treated with efalizumab. Close monitoring of all blood cell counts is warranted in light of this case.

A favourable benefit/risk ratio with efalizumab: a review of the clinical evidence

Moderate to severe plaque psoriasis has traditionally been treated with agents that have toxicities associated with long-term use. Many patients therefore cannot be treated safely, conveniently or effectively with traditional therapies. Recent phase 3 clinical trials for efalizumab, a biological agent targeted specifically at the T-cell-based pathology of psoriasis, have demonstrated its short- and long-term efficacy and safety for the treatment of psoriasis. This article reviews results from 12-week, six-month, and three-year trials, focusing on the drug's safety, efficacy, and therapeutic response time, as well as the phenomenon of rebound in non-responding patients. Efalizumab emerges as an important addition to the dermatological pharmacopeia for the long-term treatment of psoriasis.

Regulation of dextran sodium sulfate induced colitis by leukocyte beta 2 integrins

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders whose etiology remains unknown. Reports have shown that infiltration of leukocytes into intestinal tissue is a pathognomonic hallmark for this disease. Leukocyte beta(2) integrins are heterodimeric adhesion membrane proteins that are exclusively expressed on leukocytes and participate in immune cell adhesion and activation. In this study, we examined the pathophysiological role of the beta(2) integrins CD18, CD11a, and CD11b in the pathogenesis of dextran sodium sulfte (DSS)-induced experimental colitis. Disease activity was measured by daily assessment of clinical parameters including stool consistency, weight loss, occult blood, and gross rectal bleeding. Histopathological changes including severity of inflammation, surface epithelial/crypt damage, and depth of injury were also determined. The CD18 null and CD11a null mice had significantly lower disease activity and cumulative histopathological scores compared to wild-type mice. Interestingly, CD11b null mice did not show protection against DSS colitis and displayed increased disease activity compared to wild-type mice. Examination of specific leukocyte populations in the distal colon from various mice revealed significant attenuation of neutrophil and macrophage infiltrates in CD18, CD11a, and CD11b null mice. Surprisingly, the CD11b null mice showed a significant increase in plasma cell infiltration in response to DSS suggesting that this molecule may influence plasma cell function during colitis. This study demonstrates that genetic loss of CD18 or CD11a is protective during experimental colitis and that CD11b may serve a regulatory role during development of disease.