Low affinity binding of an LFA-3/IgG1 fusion protein to CD2+ T cells is independent of cell activation

The Remittive Effects of Alefacept

The duration of response to treatment with alefacept has been assessed in patients with moderate to severe chronic plaque psoriasis who responded to alefacept therapy in phase 2 and phase 3 clinical studies. In a phase 2 trial, duration of response was based on time to retreatment with alefacept. In two phase 3 studies, the more objective measure of maintenance of a ≥50% reduction from baseline Psoriasis Area and Severity Index (PASI 50) was used. Two patient subsets were analyzed: (1) those who achieved a PASI 75 at any time during the trials and (2) those who achieved a Physician Global Assessment of “clear” or “almost clear” at any time during the trials. Regardless of the criterion used or the route of alefacept administration (intravenous or intramuscular), the median duration of response to alefacept therapy ranged from 7 to 10 months across the three studies. Alefacept is a remittive therapy for psoriasis.

Can We Repurpose FDA-Approved Alefacept to Diminish the HIV Reservoir?

Current anti-retroviral treatment (ART) for HIV is effective in maintaining HIV at undetectable levels. However, cessation of ART results in immediate and brisk rebound of viremia to high levels. This rebound is driven by an HIV reservoir mainly enriched in memory CD4+ T cells. In order to provide any form of functional HIV Cure, elimination of this viral reservoir has become the focus of current HIV cure strategies. Alefacept was initially developed for the treatment of chronic plaque psoriasis. Alefacept is a chimeric fusion protein consisting of the CD2-binding portion of human leukocyte function antigen-3 (LFA3) linked to the Fc region of human IgG1 (LFA3-Fc). Alefacept was designed to inhibit memory T cell activation that contributes to the chronic autoimmune disease psoriasis by blocking the CD2 coreceptor. However, it was found to deplete memory T cells that express high levels of CD2 via NK cell-mediated antibody dependent cell cytotoxicity (ADCC) in vivo. Phase II and phase III clinical trials of alefacept with psoriasis patients demonstrated promising results and an excellent safety profile. Subsequently, alefacept has been successfully repurposed for other memory T cell-mediated autoimmune diseases including skin diseases other than psoriasis, organ transplantation and type I diabetes (T1D). Herein, we review our specific strategy to repurpose the FDA approved biologic alefacept to decrease and hopefully someday eliminate the HIV reservoir, for which CD2hi memory CD4+ T cells are a significant contributor.

Alefacept combined with tacrolimus, mycophenolate mofetil and steroids in de novo kidney transplantation: a randomized controlled trial

Memory T cells play a central role in mediating allograft rejection and are a rational target for immunosuppressive therapy. Alefacept is a recombinant LFA3/IgG1 fusion protein that reduces the number of memory T cells in both psoriatic lesions and the peripheral circulation of psoriasis patients. This study evaluated the efficacy and safety of alefacept compared with placebo when combined with tacrolimus, mycophenolate mofetil and corticosteroids in de novo renal transplant recipients. Between December 2007 and March 2009 patients were randomized in a double-blind fashion to receive alefacept (n = 105) or placebo (n = 107) for 3 months and were then followed for a further 3 months. The primary efficacy endpoint was the incidence of biopsy-confirmed acute T cell mediated rejection (Banff grade ≥ 1) through Month 6. Memory T cell counts were significantly reduced in the alefacept group from Week 3 to study end compared with placebo. However, there was no significant difference between the alefacept and placebo groups for the primary efficacy endpoint (alefacept, 11.0% vs. placebo, 7.0%, p = 0.3). Patient and graft survival as well as renal function was similar between treatment groups. Safety and tolerability were generally similar between the treatment arms. Malignancy was higher in the alefacept treatment arm.

Selective targeting of human alloresponsive CD8+ effector memory T cells based on CD2 expression

Costimulation blockade (CoB), specifically CD28/B7 inhibition with belatacept, is an emerging clinical replacement for calcineurin inhibitor-based immunosuppression in allotransplantation. However, there is accumulating evidence that belatacept incompletely controls alloreactive T cells that lose CD28 expression during terminal differentiation. We have recently shown that the CD2-specific fusion protein alefacept controls costimulation blockade-resistant allograft rejection in nonhuman primates. Here, we have investigated the relationship between human alloreactive T cells, costimulation blockade sensitivity and CD2 expression to determine whether these findings warrant potential clinical translation. Using polychromatic flow cytometry, we found that CD8(+) effector memory T cells are distinctly high CD2 and low CD28 expressors. Alloresponsive CD8(+) CD2(hi) CD28(-) T cells contained the highest proportion of cells with polyfunctional cytokine (IFNγ, TNF and IL-2) and cytotoxic effector molecule (CD107a and granzyme B) expression capability. Treatment with belatacept in vitro incompletely attenuated allospecific proliferation, but alefacept inhibited belatacept-resistant proliferation. These results suggest that highly alloreactive effector T cells exert their late stage functions without reliance on ongoing CD28/B7 costimulation. Their high CD2 expression increases their susceptibility to alefacept. These studies combined with in vivo nonhuman primate data provide a rationale for translation of an immunosuppression regimen pairing alefacept and belatacept to human renal transplantation.

Quantification and modeling of tripartite CD2-, CD58FC chimera (alefacept)-, and CD16-mediated cell adhesion

Alefacept is a chimeric protein combining CD58 immunoglobulin-like domain 1 with human IgG1 Fc. Alefacept mediates adhesion by bridging CD2 on T cells to activating Fc receptors on effector cells, but the equilibrium binding parameters have not been determined. Alefacept mediated T cell killing by NK cells and adhesion between CD2- and CD16-expressing cells at an optimum concentration of 100 nM. We introduce novel measurements with supported planer bilayers, from which key two-dimensional and three-dimensional parameters can be determined by data fitting. Alefacept competitively inhibited cell bilayer adhesion mediated by the CD2-CD58 interaction. Alefacept mediated maximal adhesion of CD2(+) T cells to CD16B, an Fc receptor, in planar bilayers at 500 nM. A mechanistic model for alefacept-mediated cell-bilayer adhesion allowed fitting of the data and determination of two-dimensional binding parameters. These included the density of bonds in the adhesion area, which grew to maintain a consistent average bond density of 200 molecules/microm(2) and two-dimensional association constants of 3.1 and 630 microm(2) for bivalently and monovalently bound forms of alefacept, respectively. The maximum number of CD16 bound and the fit value of 4,350 CD2 per cell are much lower than the 40,000 CD2 per cell measured with anti-CD2 Fab. These results suggest that additional information is needed to correctly predict Alefacept-mediated bridge formation.

Biologic agents in psoriasis

This paper reviews the new biologic agents that selectively block the immunologic steps implicated in the pathogenesis of psoriasis. Four strategies have been targeted: reduction of the number of pathogenic T cells; inhibition of T-cell activation and migration; modulation of the immune system; and blockage of the activity of inflammatory cytokines. There are three classes: monoclonal antibodies, fusion proteins and recombinant cytokines or growth factors. The actions, efficacy and side-effect profile of the biologic agents, alefacept, efalizumab, etanercept and infliximab, are reviewed.

An open-label study of alefacept plus ultraviolet B light as combination therapy for chronic plaque psoriasis

BACKGROUND

Alefacept, a fully human LFA-3/IgG(1) fusion protein, is a selective biological agent approved in the United States for the treatment of chronic plaque psoriasis. In phase 3 trials, clinical improvement and prolonged off-treatment remission of psoriasis correlated with reductions in circulating memory T cells. Reductions in pathogenic epidermal T cells in psoriatic lesions also have been noted following phototherapy with ultraviolet B (UVB) light. Because alefacept and UVB target T cells in different ways, combination therapy with these two agents may lead to greater efficacy.

OBJECTIVES

To determine the safety, tolerability, and efficacy trends of combination therapy with alefacept plus UVB light in patients with chronic plaque psoriasis.

METHODS

In an open-label, parallel-group study conducted at two sites, one in France and one in the United States, patients with chronic plaque psoriasis who were candidates for phototherapy received 12-weekly intramuscular injections of alefacept, 15 mg. In addition, patients were randomized to one of three treatment arms: no UVB treatment, 6-week UVB treatment, and 12-week UVB treatment. UVB treatment consisted of narrowband (NB) UVB at the site in France and broadband (BB) UVB at the site in the United States. The 12-week treatment period was followed by a 12-week follow-up period. Clinic visits occurred weekly during treatment and every 2-4 weeks during follow-up.

RESULTS

A total of 60 patients (n = 30/site) were enrolled in the study. Alefacept was well tolerated when administered in combination with UVB treatment and as monotherapy. There was no evidence of increased phototoxicity or photosensitivity with the combination. At each study site, alefacept/UVB provided a higher overall response rate and led to a more rapid onset of response compared with alefacept monotherapy. Of patients who achieved > or = 50% reduction from baseline Psoriasis Area Severity Index (PASI 50) at 2 weeks after the last dose of alefacept, 75-100% in the combination therapy groups maintained this response throughout follow-up in the absence of further psoriasis therapy.

CONCLUSIONS

In patients with chronic plaque psoriasis, combination therapy with alefacept plus short-term (6-12 weeks) UVB treatment is well tolerated with a trend toward greater and more rapid efficacy than alefacept alone.

The remittive effects of alefacept

The duration of response to treatment with alefacept has been assessed in patients with moderate to severe chronic plaque psoriasis who responded to alefacept therapy in phase 2 and phase 3 clinical studies. In a phase 2 trial, duration of response was based on time to retreatment with alefacept. In two phase 3 studies, the more objective measure of maintenance of a > or =50% reduction from baseline Psoriasis Area and Severity Index (PASI 50) was used. Two patient subsets were analyzed: (1) those who achieved a PASI 75 at any time during the trials and (2) those who achieved a Physician Global Assessment of "clear" or "almost clear" at any time during the trials. Regardless of the criterion used or the route of alefacept administration (intravenous or intramuscular), the median duration of response to alefacept therapy ranged from 7 to 10 months across the three studies. Alefacept is a remittive therapy for psoriasis.

The Use of Systemic Immune Moderators in Dermatology: An Update

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.

Mechanism of Action and Emerging Role of Immune Response Modifier Therapy in Dermatologic Conditions

Immune response modifiers (IRMs) are agents that target the body's immune system (i.e., cytokines, receptors, and inflammatory cells) to combat disease. Topical IRM therapies, which encompass both proinflammatory and immunosuppressive therapeutics, have been used to successfully treat a number of dermatologic conditions. Proinflammatory treatments include Toll-like receptor agonists (e.g., imiquimod 5% cream) and interferon (e.g., interferon-alpha) therapies, which have been used in the treatment of external genital warts, basal cell carcinoma, and other dermatologic diseases. Immunosuppressive therapies include topical and intralesional corticosteroids, anti-tumor necrosis factor agents (e.g., infliximab and etanercept), and anti-CD4+ T-cell agents, including calcineurin inhibitors and mycophenolate. These agents have been used to treat a number of conditions, including atopic and seborrheic dermatitis and psoriasis. This article reviews the mechanism of action of IRMs and the application of IRMs in several dermatologic diseases.

Current concepts and review of alefacept in the treatment of psoriasis

Alefacept is a novel biologic agent that selectively targets the memory T-cell population involved in the pathogenesis of psoriasis. Alefacept, administered by intramuscular (IM)or intravenous (IV) bolus injection, is safe and efficacious and improves quality of life ina broad spectrum of psoriasis patients. Disease remissions last approximately 7 months in responders following either IM or IV administration without further treatment. In clinical studies, treatment of patients with psoriasis with up to six courses of alefacept demonstrates the following: no evidence of an increased risk for infection or malignancy;no correlation between rates of infection, malignancy, and circulating CD4+ /CD8+ T-cell counts; and low immunogenicity. A preliminary study evaluating the use of alefacept for the treatment of active psoriatic arthritis parallels the psoriasis experience and supports the premise of targeting T cells as an intervention for this disease. Research continues to examine the use of alefacept in combination with other systemic psoriasis therapies and phototherapy and its potential as a treatment for other T-cell-mediated diseases, such as psoriatic arthritis, alopecia areata, and rheumatoid arthritis.

Improved health-related quality of life following a randomized controlled trial of alefacept treatment in patients with chronic plaque psoriasis

BACKGROUND

Psoriasis has a negative impact on patients' quality of life. Treatment strategies should address both the cutaneous manifestations of the disease and their impact on quality of life.

OBJECTIVES

To evaluate the effect of alefacept on quality of life in 553 patients with chronic plaque psoriasis.

METHODS

In this multicentre, double-blind, parallel-groups study, patients were randomized to receive alefacept for two courses, alefacept in course 1 and placebo in course 2, or placebo in course 1 and alefacept in course 2. In each course, alefacept 7.5 mg or placebo was administered once weekly by 30-s intravenous injection for 12 weeks followed by 12 weeks of observation. The Dermatology Life Quality Index (DLQI), Dermatology Quality of Life Scales (DQOLS) and Short Form-36 Health Survey (SF-36) were administered at baseline, 2 weeks after the last dose in both courses, at the beginning of course 2, and at the end of the observation period in both courses.

RESULTS

In course 1, alefacept significantly reduced (improved) mean DLQI scores compared with placebo: 4.4 vs. 1.8 at 2 weeks after the last dose (P<0.0001) and 3.4 vs. 1.4 at 12 weeks after the last dose (P<0.001). Patients who received two courses of alefacept experienced additional enhancement of quality of life measures during the second course. Similar results were observed for the DQOLS. The SF-36 survey confirmed that alefacept had no negative impact on general quality of life.

CONCLUSIONS

Alefacept improved quality of life in patients with chronic plaque psoriasis and maintained this benefit for at least 12 weeks following cessation of treatment. A second course of alefacept provided additional quality of life benefit.

CD4+ T-cell–directed antibody responses are maintained in patients with psoriasis receiving alefacept: results of a randomized study

BACKGROUND

Alefacept, human LFA-3/IgG(1) fusion protein, selectively reduces memory-effector (CD45RO(+)) T cells, a source of the pathogenic mediators of psoriasis.

OBJECTIVE

To evaluate the effect of alefacept on immune function, T-cell-dependent humoral responses to a neoantigen (PhiX174) and recall antigen (tetanus toxoid) were assessed.

METHODS

Patients with psoriasis were randomized to the control group or to receive alefacept (7.5 mg intravenously weekly for 12 weeks). The alefacept group received PhiX174 immunizations at weeks 6, 12, 20, and 26 and tetanus toxoid at week 21; control subjects received PhiX174 at weeks 6 and 12 and tetanus at week 10.

RESULTS

Mean anti-PhiX174 titers were comparable in both groups. There was no difference in the percentage of responders (anti-PhiX174 IgG >/=30% of the total anti-PhiX174) between the alefacept group and the control group (86% and 82%, respectively; P =.73). The percentage of patients with anti-tetanus toxoid titer increases >/=2 times baseline also was similar (alefacept, 89%; control 91%).

CONCLUSION

A single 12-week course of alefacept did not impair primary or secondary antibody responses to a neoantigen or memory responses to a recall antigen. The selective immunomodulatory effect of alefacept against a potentially pathogenic T-cell subset is associated with maintenance of a significant aspect of immune function (antibody response) to fight infection and respond to vaccinations.

Evolution of biologic therapies for the treatment of psoriasis

Over the past three decades, laboratory and clinical research findings have shown that T cells are the primary mediators of psoriasis pathogenesis and that psoriasis can be treated by eliminating these T cells or interfering with their activation or activity. Based on these observations, many new biologic therapies to treat psoriasis are now in development. These agents, developed primarily through recombinant DNA techniques, are designed to target T cells and the immunologic cascade associated with their activation. Four basic strategic approaches that focus on the steps involved in the immunopathology of psoriasis are: 1) elimination of the pathogenic T cells; 2) inhibition of T-cell activation, proliferation, and migration; 3) immune deviation to down-regulate the type 1 (TH1) response predominant in psoriasis; and 4) blockade of cytokine production. The goal of these new therapies is to improve the treatment of psoriasis, particularly moderate to severe disease, with agents that are well tolerated and safe for long-term use.

Development and use of alefacept to treat psoriasis

Activated memory T cells, expressing CD2, are key components in the pathogenesis of psoriasis. Alefacept binds to CD2, blocks co-stimulatory signaling, and selectively induces apoptosis of pathogenic T cells. Our objective is to present safety and efficacy results which lead to the new drug application (NDA) of alefacept for the treatment of psoriasis. We reviewed the key phase II and III trials in over 1300 patients and found that during treatment and follow-up of patients receiving 12 weekly intramuscular or intravenous injections of alefacept, about 1/3 will achieve a reduction in psoriasis area and severity index (PASI) of > or =75% and nearly 2/3 a reduction in PASI of > or =50%. Patients who achieved a > or =75% reduction from baseline PASI during or after a single course maintained a > or =50% reduction in PASI for a median duration of >7 months. Among patients who received 2 courses of alefacept, 40% and 71% of patients achieved a > or =75% and > or =50% reduction in PASI, respectively and duration of effect was prolonged. Adverse events in the placebo and active treatment arms did not differ. We conclude that alefacept significantly improves psoriasis and produces durable clinical improvement with a very favorable safety profile.

The role of T cells in psoriasis

Evidence for a key role of T cells in the pathogenesis of psoriasis has come from both experimental and clinical data. Initially, generalized immunosuppressants, intended for use in transplant settings, were found to improve clinical signs and symptoms of psoriasis. Their efficacy attracted attention to the activated T cells that are a major component of the inflammatory infiltrate of psoriatic lesions. Further research determined that T cells from patients with psoriasis could transmit disease in animal models. These findings laid the groundwork for characterizing the pathogenesis of psoriasis as immune mediated with skin-directed T cells playing a central role. Once these pathogenic T cells have entered the skin, they become activated and release cytokines and chemokines to attract other immune cells to perpetuate the inflammatory cascade. As the role of the T cell in psoriasis has evolved and understanding of immunopathology has increased, a multitude of biologic targets have been revealed. Newer strategies for the treatment of psoriasis have therefore focused on modifying T cells in this disease through direct elimination of activated T cells, inhibition of T-cell activation, or inhibition of cytokine secretion or activity. The mechanisms by which these new biologic agents act on psoriasis will affect their profile of efficacy and safety. Important selection criteria for optimal antipsoriatic therapies include long-term safety and tolerability, ability to produce long-lasting remissions, and convenient dosing regimens.

Alefacept therapy produces remission for patients with chronic plaque psoriasis

BACKGROUND

Alefacept, human LFA-3/IgG1 fusion protein, is a novel biological agent currently being developed for the treatment of chronic plaque psoriasis. Alefacept selectively reduces the memory-effector T cells that have been implicated in the pathogenesis of the disease; as a result, alefacept is classified as a therapy that induces remission (so-called 'remittive' therapy). In a previously published randomized, placebo-controlled phase II study of intravenous alefacept in 229 patients with chronic plaque psoriasis, clinical improvement was observed during dosing as well as in the postdosing follow-up period.

OBJECTIVES

To assess the remission period following alefacept therapy.

METHODS

The time before re-treatment was required was measured in patients who were 'clear' or 'almost clear' of disease according to a physician global assessment at the end of the follow-up phase.

RESULTS

In these patients, responses were sustained for a median of 10 months, and for up to 18 months. No patient reported disease rebound after cessation of alefacept.

CONCLUSIONS

Alefacept is a biological agent for the treatment of chronic plaque psoriasis that provides disease-free intervals and time off drug therapy.

Repeat courses of intravenous alefacept in patients with chronic plaque psoriasis provide consistent safety and efficacy

BACKGROUND

Psoriasis is a chronic, relapsing skin disease that may require multiple treatment courses. Alefacept targets the memory T cells implicated in psoriasis pathogenesis. This open-label study evaluated the safety and tolerability, efficacy, and pharmacodynamics of repeat courses of alefacept in men and women with chronic plaque psoriasis. This article reports the interim results of this ongoing study.

METHODS

Patients (n = 174) who participated in previous phase II studies of alefacept were included in this retreatment study. Intravenous alefacept (7.5 mg) was administered once weekly for 12 weeks followed by 12 weeks of observation. Initial and subsequent retreatment courses were only given when, in the opinion of the investigators, disease had returned and necessitated treatment; CD4+ T-cell counts had to be at or above the lower limit of normal.

RESULTS

Adverse events were similar regardless of the retreatment course. No opportunistic infections, rebound of disease, or flares were reported. Low titers of anti-alefacept antibodies occurred in a few patients without related safety issues. Sixty-six per cent of patients achieved a >/= 50% reduction in the Psoriasis Area and Severity Index (PASI) at any time after the first dose of retreatment course 1. Patients who received two retreatment courses (n = 50) had consistent or improved responses after the second course; 64% and 68% of these patients achieved a >/= 50% PASI improvement at any time after the first dose of retreatment courses 1 and 2, respectively. Alefacept selectively reduced memory T cells without cumulative effects.

CONCLUSIONS

Repeat courses of alefacept were well tolerated, and subsequent retreatment courses were at least as effective as the initial course of therapy.

Pharmacokinetics, biologic activity, and tolerability of alefacept by intravenous and intramuscular administration

Alefacept, human LFA-3/IgG1 fusion protein, is currently under clinical development for the treatment of chronic plaque psoriasis and other T cell mediated disorders. This recombinant protein binds CD2 on T cells and Fc gamma RIII on accessory cells (e.g., natural killer cells, macrophages), inhibiting T cell activation/proliferation and inducing selective T cell apoptosis. These effects are associated with selective reductions in memory-effector (CD4+ CD45RO+ and CD8+ CD45RO+) T cells. Two open-label studies were conducted in healthy male volunteers to evaluate the pharmacokinetics, biologic activity, and tolerability of a single dose of alefacept when administered as a 0.15 mg/kg 30-sec i.v. bolus (n = 12), 0.04 mg/kg intramuscular (i.m.) injection (n = 8), or 0.04 mg/kg 30-min intravenous (i.v.) infusion (n = 8). i.v. infusion produced a higher Cmax (0.96 +/- 0.26 mcg/ml vs. 0.36 +/- 0.19 mcg/ml) and a shorter Tmax (2.8 +/- 1.9 hr vs. 86 +/- 60 hr) when compared to i.m. injection. Based on AUC0-last and AUC0-infenity values, the relative bioavailability of i.m. to i.v. infusion was approximately 60%. After absorption from the i.m. injection was complete, the rate of alefacept elimination from the serum appeared consistent with the i.v. infusion half-life (approximately 12 days). Biologic activity was demonstrated by transient reductions in absolute number of CD2+ lymphocytes, with notable specificity for memory T-cell subsets. Alefacept was well tolerated; the most common adverse effects were headache, pharyngitis, rash, and myalgia. IM administration was not associated with significant local reactions. Results of these studies support i.v. bolus or i.m. administration of alefacept. An i.m. dose of approximately 150 to 200% of the i.v. dose is an appropriate and convenient alternative to i.v. administration.

Alefacept, an immunomodulatory recombinant LFA-3/IgG1 fusion protein, induces CD16 signaling and CD2/CD16-dependent apoptosis of CD2(+) cells

Alefacept, an immunomodulatory recombinant fusion protein composed of the first extracellular domain of LFA-3 fused to the human IgG1 hinge, C(H)2, and C(H)3 domains, has recently been shown in phase II and III clinical trials to safely reduce disease expression in patients with chronic plaque psoriasis. Alefacept modulates the function of and selectively induces apoptosis of CD2(+) human memory-effector T cells in vivo. We have sought to gain further understanding of the mechanisms of action that influence the biological activity of alefacept and may contribute to its efficacy and patient responsiveness. Specifically evaluated is the ability of alefacept to activate intracellular signals mediated via CD2 and/or Fc gamma RIII (CD16). Experimentation using isoforms of alefacept engineered to have amino acid substitutions in the IgG1 C(H)2 domain that impact Fc gamma R binding indicate that alefacept mediates cognate interactions between cells expressing human CD2 and CD16 to activate cells, e.g., increase extracellular signal-regulated kinase phosphorylation, up-regulate cell surface expression of the activation marker CD25, and induce release of granzyme B. In the systems used, this signaling is shown to require binding to CD2 and CD16 and be mediated through CD16, but not CD2. Experimentation using human CD2-transgenic mice and isoforms of alefacept confirmed the requirement for Fc gamma R binding for detection of the pharmacological effects of alefacept in vivo. Thus alefacept acts as an effector molecule, mediating cognate interactions to activate Fc gamma R(+) cells (e.g., NK cells) to induce apoptosis of sensitive CD2(+) target cells.

Selective targeting of T cell subsets: focus on alefacept - a remittive therapy for psoriasis

Psoriasis is an immune-mediated disease in which memory-effector (CD45RO+), skin-homing T cells play a key role in driving the disease process. Available therapies are often poorly tolerated, none are curative and most only suppress disease symptoms without attacking the underlying cause of the illness. Alefacept (Ameviv, Biogen, Inc.) is a fully human lymphocyte function associated antigen-3/immunoglobulin G1 fusion protein that targets memory-effector T cells by binding CD2 on the T cell and Fc phi receptor III IgG receptors on accessory cells, thereby preventing T cell activation and proliferation and causing selective T cell apoptosis. To date, alefacept has been studied in moderate-to-severe chronic plaque psoriasis and in a pilot study of psoriatic arthritis. In chronic plaque psoriasis, alefacept produced significant and sustained improvements in psoriasis symptoms. There was no evidence of disease rebound or worsening of psoriasis following treatment cessation. Multiple courses provided consistent efficacy, with a trend for more rapid and greater clinical improvement in subsequent courses. Alefacept reduced circulating CD4+ and CD8+ memory-effector T cells, with relatively no change in naive (CD45RA+) T cells or B cells. Alefacept also reduced IFN-phi-secreting Tcells in lesional biopsies of psoriatic skin. These reductions all correlated with the observed clinical effect. Alefacept was well-tolerated throughout these studies, with a side effect profile similar to placebo. There was no evidence of generalised immunosuppression or increased risk of infection or malignancy. Alefacept did not alter the primary or acquired immune response in psoriatic patients. Clinical data obtained to date support the use of alefacept as a safe and remittive therapy for psoriasis.

Analysis of mono- and oligosaccharides by multiwavelength surface plasmon resonance (SPR) spectroscopy

Surface plasmon resonance (SPR) spectra of different saccharides were collected using a home-made multiwavelength SPR apparatus. Pentoses, hexoses, disaccharides and a trisaccharide were distinguished from one another according to their SPR spectra collected at the same concentration. The spectra were also used for the quantitation of sugars by exploring the linear relationship between resonance wavelength and solute concentration. The dynamic linear ranges for the determination of glucose, sucrose and raffinose are 0.01-0.2, 0.005-0.1 and 0.0025-0.1 mol/L, respectively. The SPR spectrum of a mixture of two components was investigated. While the experiments have not been carried out, the implications from this work are that the technique would be applicable to mixtures containing more than two components.

Survey of the 1999 surface plasmon resonance biosensor literature

The application of surface plasmon resonance biosensors in life sciences and pharmaceutical research continues to increase. This review provides a comprehensive list of the commercial 1999 SPR biosensor literature and highlights emerging applications that are of general interest to users of the technology. Given the variability in the quality of published biosensor data, we present some general guidelines to help increase confidence in the results reported from biosensor analyses.