Immunological effects of high dose administration of anti-CD4 antibody in rheumatoid arthritis patients

Biological Assessment and Mri Monitoring of the Therapeutic Efficacy of a Monoclonal Anti-T Cd4 Antibody in Multiple Sclerosis Patients

An initial group of 21 patients plus a second group of 14 patients with active multiple sclerosis (MS) (18 progressive and 17 relapsing-remitting forms) were treated with a murine monoclonal anti-T CD4/BF5 antibody as part of a phase 1 open trial. Tolerance was relatively good: minor general side-effects occurred in 22 patients only upon the first mAb infusion. One year later, functional disability was stabilised in only six of the 35 patients and after 2 years in two patients only (among 21). One year after treatment, nine of the 17 relapsing-remitting patients were relapse-free. CD4 counts decreased dramatically 2 h after treatment These counts were back to baseline counts at 3 months. A transient increase was found in IL-6 and TNFα levels 2 h after treatment, which probably accounts for the observed side effects. Cell adhesion molecule levels were not modified. Serial MRI scans were performed in the second group of 14 patients. In all of these patients, lesion modifications were observed in the three scans performed prior to treatment Yet, no changes in the lesions were noted on the MRI scans performed over the following 3 months. These findings demonstrate the feasibility of this treatment insofar as it induced a marked CD4 lymphocyte depletion. However, it did not seem to stabilise the evolution of the disease – although one must be careful in drawing such conclusions in a phase 1 trial – or to curb the evolution of MRI-documented lesions.

Cytapheresis with a filter for selective removal of CD4+ T cells in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a major animal model of human multiple sclerosis (MS). CD4+ T cells are thought to play a pivotal role in the patho genesis of EAE and MS. In order to investigate the depletio n of CD4+ T cells from the systemic circulation as an effective strategy for the treatment of MS, we performed extracorporeal CD4+ T cell adsorption, using a filter to which anti-CD4+ antibody is immobilized as a ligand, in adoptively transferred EAE. Rats treated with CD4+ T cell removal filter (C D4RF) exhibited milder clinical signs of EAE and earlier recovery than those receiving sham treatment. Moreover, the thymic cells from EAE rats treated with C D4RF exhibited a suppressed proliferative response and IFN-g production to myelin basic protein. These results suggest that depletion of CD4+ T cells from the systemic circulation by extracorporeal treatment is a potentially useful strategy for treatment of acute phase and relapsing MS.

Biologic therapies in rheumatology: lessons learned, future directions

During the past decade biologic therapies such as monoclonal antibodies and fusion proteins have revolutionized the management of rheumatic disease. By targeting key cytokines and immune cells biologics have provided more specific therapeutic interventions with less immunosuppression. Clinical use, however, has revealed that their theoretical simplicity hides a more complex reality. Efficacy, toxicity and even pharmacodynamic effects can deviate from those predicted, as poignantly illustrated by the catastrophic effects witnessed during the first-into-human administration of TGN1412. This review summarizes lessons gleaned from practical experience and discusses how these can inform future discovery and development of new biologic therapies for rheumatology.

Selective Adsorption of Human CD4+ T Cells

The pathogenesis of most autoimmune diseases directly involves CD4(+) helper T cells. To remove CD4(+) T cells selectively from the circulation, we designed a new column in which an anti-CD4 monoclonal antibody was immobilized on the activated substance. Nearly 90% of CD4(+) T cells were selectively adsorbed from whole blood with a single passage through the column in vitro, resulting in depletion of the antigen-specific T cell responses. We conclude that this new column would be potentially useful for treatment of T cell-mediated autoimmune diseases.

The therapeutic potential of costimulatory blockade with CTLA4Ig in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory disorder characterised by joint inflammation and destruction. Controversy exists regarding the significance and exact role of activated T cells in RA. CTLA4Ig is a soluble fusion protein (cytotoxic T lymphocyte-associated antigen 4 fused to the heavy chain constant region of human IgG1), which represents the first in a new class of agents called costimulation blockers. By blocking the second signal required for optimal T-cell activation, CTLA4Ig has demonstrated efficacy in a variety of spontaneous and induced animal models of autoimmunity. A Phase II clinical study in RA showed CTLA4Ig was efficacious with an acceptable safety profile. These results suggest that activated T cells may be important in RA pathogenesis and that costimulation blockade may be a novel therapeutic approach for this disorder.

The use of monoclonal antibodies to restore self-tolerance in established autoimmunity

The author hopes to convince the reader that the data presented argue for a stage during the development of IDDM when beta-cell destruction can be counteracted and tolerance to beta cells restored, provided the immune aggression is arrested. This argument constitutes a solid rationale for immunointervention in established IDDM, especially by using potent agents such as CD3. The future for the application of monoclonal antibodies not only in autoimmunity but also in transplantation is exiting. With the development of humanized monoclonal antibodies, therapeutic uses for them are likely to expand. Enormous progress has been made in the last 15 years, and it is likely that before a similar time period has elapsed, monoclonal antibodies will have become standard tools that will dispense the need for long-term immunosuppression and its inherent dangers in various clinical arenas.

Investigational treatments in rheumatoid arthritis

The active search for new treatment modalities of established rheumatoid arthritis have created a dynamic period for rheumatology. Both promising pharmaceutical products and targeted interventions with products of the biotechnology industry are being developed. Leflunomide and the selective blockade of the cytokine tumour necrosis factor (TNF) have recently been registered in several countries and others will follow. Like all new therapeutic strategies much remains to be learned about the optimal use of these therapies and their possible limitations. The success of these interventions have shown that a complex disease such as rheumatoid arthritis that is refractory to conventional treatment can be modulated by new therapeutic strategies. This experience has also resulted in further searches for new drugs that influence those pathogenetic pathways affected by the interventions found to be effective.

Intra-articular primatised anti-CD4: efficacy in resistant rheumatoid knees. A study of combined arthroscopy, magnetic resonance imaging, and histology

OBJECTIVES

CD4+ T cells sustain the chronic synovial inflammatory response in rheumatoid arthritis (RA). SB-210396/CE 9.1 is an anti-CD4 monoclonal antibody that has documented efficacy in RA when given intravenously. This study aimed to establish the safety and efficacy of the intra-articular administration of SB-210396/CE 9.1 compared with placebo, examining its mode of action using a combined imaging approach of arthroscopy, magnetic resonance imaging (MRI), and histology.

METHODS

Thirteen RA patients with active, resistant knee synovitis, were randomised to intra-articular injection of placebo (n=3), 0.4 mg (n=3) or 40 mg (n=7) of anti-CD4 after sequential dynamic gadolinium enhanced MRI, followed by same day arthroscopy and synovial membrane biopsy. Imaging and arthroscopic synovial membrane sampling were repeated at six weeks. This study used a unique region of interest (ROI) analysis mapping the MRI area analysed to the specific biopsy site identified arthroscopically, thus providing data for all three modalities at the same synovial membrane site.

RESULTS

12 patients completed the study (one placebo treated patient refused further MRI). Arthroscopic improvement was observed in 0 of 2 placebo patients but in 10 of 10 patients receiving active drug (>20% in 6 of 10). Improvement in MRI was consistently observed in all patients of the 40 mg group but not in the other two groups. A reduction in SM CD4+ score was noted in the 40 mg group and in the 0.4 mg group. Strong correlations both before and after treatment, were identified between the three imaging modalities. Intra-articular delivery of SB-210396/CE 9.1 was well tolerated.

CONCLUSIONS

SB-210396/CE 9.1 is safe when administered by intra-articular injection. A trend toward efficacy was found by coordinated MRI, arthroscopic, and histological imaging, not seen in the placebo group. The value of ROI analysis was demonstrated.

Anti-ICAM-1 Monoclonal Antibody R6.5 (Enlimomab) Promotes Activation of Neutrophils in Whole Blood

R6.5 (BIRR-1, Enlimomab), a murine IgG2a mAb to the human ICAM-1, inhibits leukocyte adhesion to the vascular endothelium, thereby decreasing leukocyte extravasation and inflammatory tissue injury. In initial clinical trials, R6.5 proved to be beneficial in reducing both disease activity in refractory rheumatoid arthritis and the incidence of acute rejection after kidney and liver allograft transplantations. However, adverse effects such as fever, leukopenia, or cutaneous reactions were not infrequent. We studied the effects of R6.5 on neutrophil function in whole blood samples ex vivo. Surprisingly, at the concentrations achieved in clinical trials, R6.5 activated neutrophilic granulocytes, as indicated by a significant increase in expression of the adhesion molecule β2-integrin CD11b, a concurrent decrease in L-selectin expression, and an enhancement of the oxidative burst activity. Neutrophil activation was not exerted by an anti-ICAM-1 mAb of the IgG1 isotype, by isotype-matched, irrelevant anti-2-phenyloxazolone mAb, or by F(ab′)2 fragments of R6.5. Neutrophil activation was completely inhibited by soluble complement receptor type 1. We conclude that in whole blood, R6.5 activates resting neutrophils in a complement-dependent manner. This finding can explain, at least in part, the side effects associated with R6.5 therapy.

Cyclosporin A and FK-506 inhibit development of superantigen-potentiated collagen-induced arthritis in mice

1. Staphylococcal enterotoxine B (SEB; superantigen) accelerated the onset of arthritis in mice preimmunized with type II collagen (SEB-potentiated collagen-induced arthritis). Cyclosporin A and FK-506 inhibited the induction and development of clinical signs and histopathological changes of SEB-potentiated collagen-induced arthritis in mice. 2. Simultaneously, both cyclosporin A and FK-506 inhibited the development of humoral and cellular immunity to type II collagen. 3. The expression of IL-2 receptor (CD25) by SEB on splenocyte T cells from collagen-preimmunized mice was inhibited by both agents in ex vivo experimentation.

Humanized anti-CD4 monoclonal antibody therapy of autoimmune and inflammatory disease

We have investigated the biological and therapeutic properties of a humanized anti-CD4 MoAb, hIgG1-CD4, in patients with refractory psoriasis and rheumatoid arthritis (RA). hIgG1-CD4 is a modulating, non-depleting MoAb, which induced a first-dose reaction in most patients treated. It provided brief symptomatic relief in both conditions, and psoriasis appeared easier to control with conventional agents after MoAb therapy. At the doses used, hIgG1-CD4 did not synergize therapeutically with the panlymphocyte MoAb CAMPATH-1H (C1H) in patients with RA treated sequentially with both agents. There were no serious adverse effects definitely attributable to therapy. Our results are compared with those of other CD4 MoAb studies, and factors influencing the outcome of therapy are discussed.

Anti-CD4 monoclonal antibody-induced allograft tolerance in rats despite persistence of donor-reactive T cells

Although CD4-targeted therapy abrogates acute rejection and may induce permanent graft acceptance in rodents, little is known about the mechanisms of long-term graft survival in these models. Recently, we have shown that treatment with a nondepleting anti-CD4 monoclonal antibody (mAb) (RIB-5/2) induces long-term survival of renal, heart, and skin allografts in strong major histocompatibility complex I/II incompatible rat strains. Here, we demonstrate that the development of major histocompatibility complex-specific and tissue-nonspecific tolerance rather than graft adaptation is responsible for long-term anti-CD4 mAb-induced transplant survival. Donor-specific but not third-party heart and pancreatic islet grafts were accepted permanently without adjunctive therapy in long-term kidney allograft recipients, and infusion of naive or alloimmune splenocytes failed to break the tolerant state. Interestingly, alloreactive T cells were not depleted in these long-term survivors, as ex vivo donor-specific mixed lymphocyte reaction was largely unaffected. The reverse transcriptase-polymerase chain reaction analyses of long-term renal allografts before and after donor-specific antigen challenge revealed no changes in CD3 mRNA level, but showed up-regulation of CD25, interleukin (IL) 2, interferon (IFN) gamma, IL-4, and IL-10 mRNA in the early phase, suggesting the presence of alloreactive T cells in tolerant rats. At later time points, the expression of IFN-gamma declined rapidly, whereas IL-4 persisted, resulting in a reversal of IFN-gamma/IL-4 ratio. Our data demonstrate the stability of anti-CD4 mAb-induced tolerance despite persistence of alloreactive T cells, suggesting the role of active tolerance-maintaining mechanisms. The T helper (Th) 1/Th2 shift may be involved in this regulatory process, as anti-CD4 mAb prevents acute graft-deteriorating rejection by effectively blocking Th1 responses, and well-functioning grafts may tolerize themselves by inducing regulatory cells.

A primatized MAb to human CD4 causes receptor modulation, without marked reduction in CD4+ T cells in chimpanzees: in vitro and in vivo characterization of a MAb (IDEC-CE9.1) to human CD4

A Primatized anti-CD4 monoclonal antibody (MAb), CE9.1, with V-domain from cynomolgus macaque (showing 92% homology with human consensus sequence V-domains), and a human IgG1 constant region, was characterized in vitro and in vivo in chimpanzees. This MAb binds human CD4 with Kd of 1.0 nM and was also able to bind to human IgG Fc receptors (Fc gamma R). However, despite being of the IgG1 subclass, CE9.1 did not bind to complement component C1q, nor did it mediate complement-dependent cytotoxicity. Examination of T cells from a number of species showed restricted reactivity for CE9.1, recognizing only human and chimpanzee CD4. In both human and chimpanzee MLRs, it had an IC50 of about 10.0 ng/mL. Therefore, a chimpanzee in vivo model was used to characterize CE9.1, CE9.1 caused transient decrease in the number of lymphocytes bearing the CD4 receptor starting at doses of 0.3 mg/kg in an in vivo dose ranging study in one chimpanzee. This effect was reversed within approximately 7 days. In a multiple high-dose study in which 10.0 mg/kg of CE9.1 was administered at intervals of 1-3 months, there was a dramatic loss of CD4 marker with a reciprocal increase in the number of CD3+ CD8- CD4- cells. The CD4 receptor was totally undetectable on these lymphocytes for 1-2 weeks, with a gradual, but complete, reversal within 4 weeks. We interpret these observations as receptor modulation because, although there was apparent loss of CD4+ lymphocytes, an equivalent number of CD3+CD8- T lymphocytes were present in circulation in all four chimpanzees treated with 10.0 mg/kg CE9.1. Even at this high dose, only limited reduction of CD4+ T lymphocytes was observed in these animals. These observations are in sharp contrast to what has been reported in rodents or in human clinical studies using other IgG1 mAbs to human CD4. CD8 counts, although variable, remained unaffected by CE9.1 treatment. No adverse events were observed following administration of CE9.1 to chimpanzees, and there was no detectable host immune responses to the Primatized MAb.

Treatment of experimental allergic encephalomyelitis by selective removal of CD4+ T cells

Experimental allergic encephalomyelitis (EAE) is a major animal model of human multiple sclerosis (MS). The pathogenesis of both MS and EAE directly involves CD4+ helper T cells. To remove CD4+ T cells selectively from the circulation, we designed a new column in which anti-CD4 monoclonal antibody was immobilized on the activated substance. Most of the CD4+ T cells, including pathogenic T cells, were selectively adsorbed from whole blood with a direct perfusion through the column in vitro, resulting in depletion of the antigen-specific T cell responses. A preliminary trial of ex vivo treatment with the column in EAE rats lowered the percentages of CD4+ populations but failed to alter the course of the disease, suggesting repeated treatment would be necessary to suppress the development of the disease. We conclude that this new column is potentially useful, and repeated treatment would be beneficial in MS and other CD4+ T cell dependent autoimmune diseases.

Treatment with a chimeric CD4 monoclonal antibody is associated with a relative loss of CD4+/CD45RA+ cells in patients with rheumatoid arthritis

This study investigates immunogenicity and in vivo effects on T-cells of long-term CD4 monoclonal antibody treatment of patients with rheumatoid arthritis. Patients were treated with several dosage regimens of a chimeric CD4 monoclonal antibody entitled cM-T412 over the course of 1 year. The circulating CD4+ T-cell count sharply decreased after the first cM-T412 injection and slowly recovered after the last injection. Within the CD4+ subset there was a selective depletion of CD45RA+ T cells, HLA-DR+, and CD25+ cells, providing evidence that activated/memory CD4+ cells resist the effect of CD4 monoclonal antibodies. Studies on cytokine production by peripheral blood mononuclear cells cultures in vitro revealed no differential effect on the production of interleukin-4 compared to interferon-gamma, indicating that a shift from a Th1 to a Th2 lymphokine production profile was not achieved. Human anti-monoclonal antibodies (HAMA) were induced in a minority of the patients predominantly after the first treatment course. All the sera containing HAMA specifically inhibited the binding of cM-T412 to T-cells. However, HAMA formation does not interfere with the biological effect of repeated cM-T412 administration since the degree of CD4 depletion following repeated administration of cM-T412 to patients with and without blocking antibodies was similar. We conclude that the currently available data are of critical importance in the interpretation of the obtained clinical experience and for further development of this therapeutic strategy.

CD4 mAbs prevent progression of alloactivated CD4+ T cells into the S phase of the cell cycle without interfering with early activation signals

Knowing that several CD4 mAbs may delay allograft rejection in the absence of circulating CD4+ lymphocyte depletion in vivo, we investigated the mechanisms whereby CD4 mAbs can interfere with the development of alloreactive T cells in the mixed lymphocyte reaction (MLR). In agreement with previous reports, CD4 mAbs of different species (mouse, rat, humanized), isotypes (IgG1, IgG2a, and IgG2b) and different epitope specificities decreased 3H-TdR incorporation in MLR, using monocyte-depleted or CD4+ T lymphocyte-enriched blood mononuclear cells as responders. Those effects were achieved at nonsaturating mAb concentration and were still demonstrable upon delayed addition of CD4 mAbs. However, CD4 mAbs decreased neither the number of blast cells nor the expression of CD25 (the alpha chain of IL-2 receptor), indicating that initial activation events leading to blast transformation were not affected. Determination of cytokine gene expression by non competitive quantitative RT-PCR and measurement of protein concentration in supernatants demonstrated that CD4 mAbs did not decrease IFN-gamma induced by alloactivation. However IL-2 concentration was decreased in all supernatants whereas IL-2 mRNA expression, only slightly decreased at 24 hr, and dropped after 72 hr. IL-5 and IL-10 mRNAs, equally expressed by stimulated or nonstimulated responder cells, were not affected by CD4 mAbs. IL-4 mRNA was not detectable. Furthermore, addition of rIL-2, rIFN-gamma or rIL-4 did not overcome proliferation inhibition. The data provide a novel insight into the mechanisms of CD4 mAbs immunosuppresssion that associates a decrease of IL-2 expression with an IL-2 resistant blockade of the progression of activated CD4+ T cells from the G1 to the S phases of the cell cycle.

High-avidity human IgG kappa monoclonal antibodies from a novel strain of minilocus transgenic mice

Human immunoglobulin transgenic mice provide a method of obtaining human monoclonal antibodies (Mabs) using conventional hybridoma technology. We describe a novel strain of human immunoglobulin transgenic mice and the use of this strain to generate multiple high-avidity human sequence IgG kappa Mabs directed against a human antigen. The light chain transgene is derived in part from a yeast artificial chromosome clone that includes nearly half of the germline human V kappa region. In addition, the heavy-chain transgene encodes both human mu and human gamma 1 constant regions, the latter of which is expressed via intratransgene class switching. We have used these animals to isolate human IgG kappa Mabs that are specific for the human T-cell marker CD4, have high binding avidities, and are immunosuppressive in vitro. The human Mab-secreting hybridomas display properties similar to those of wild-type mice including stability, growth, and secretion levels. Mabs with four distinct specificities were derived from a single transgenic mouse, consistent with an extensive diversity in the primary repertoire encoded by the transgenes.

The effects of mesoporphyrin on experimental arthritis in mice

The effects of mesoporphyrin, a novel porphyrin derivative, on type II collagen-induced arthritis in mice were studied. Mesoporphyrin (10-30 mg/kg) and prednisolone (5 mg/kg; reference drug) reduced the incidence and severity of type II collagen-induced arthritis in mice, as assayed by clinical observation and histopathological studies. Although both agents inhibited type II collagen-induced delayed type hypersensitivity in arthritic mice, only prednisolone inhibited humoral immunity to type II collagen. The effects of mesoporphyrin on T cell dependent allergic inflammation were examined, in order to study the mechanism by which it inhibits arthritis. Staphylococcal enterotoxin B (SEB; superantigen)-potentiated collagen-induced arthritis and sheep red blood cell-induced delayed type hypersensitivity reaction were clearly inhibited by mesoporphyrin. Moreover, the superantigen-induced CD-25 expression on T cells was inhibited by mesoporphyrin. These results indicate that mesoporphyrin inhibits type II collagen-induced arthritis by inhibiting the activation of T cells.

Biologic agents for the treatment of rheumatoid arthritis

Substantial progress has been made in our understanding of the immune system and immunopathogenesis of rheumatoid arthritis. This knowledge, combined with advances in biotechnology, has resulted in the development of biologic agents to selectively target elements of the immune system participating in the inflammatory response. This article reviews the available data from clinical trials of biologic agents for the treatment of rheumatoid arthritis. Randomized controlled trials comparing administration of a biologic agent to placebo are emphasized. Despite concerns raised by initial trials with these agents, they still offer the most promise as treatments for autoimmune diseases ++such as rheumatoid arthritis.

Prospects of immunotherapy for rheumatoid arthritis

The main challenge in the development of new modalities for the treatment of rheumatoid arthritis is to enhance the specificity while reducing the adverse side-effects of therapeutics. Biotechnology provides a variety of reagents, such as monoclonal antibodies, recombinant cytokines, cytokine antagonists, and small peptides, with the potential to interfere with selected stages of the disease process in a highly specific manner. In addition, several new therapeutic approaches have emerged as a result of extensive research with animal models of disease, including T-cell vaccination and bone marrow transplantation. This article discusses current insights into the pathogenesis of rheumatic diseases, focusing on rheumatoid arthritis. A number of new therapeutic modalities for rheumatoid arthritis, in particular those acting on the immune system, are discussed. Because it is not possible to provide a complete overview of all the developments in the field in limited space, a selection of strategies and modalities which are representative of the broad variety of immunotherapeutic approaches currently used are highlighted.

Double-blind, placebo-controlled multicenter trial using chimeric monoclonal anti-CD4 antibody, cM-T412, in rheumatoid arthritis patients receiving concomitant methotrexate

OBJECTIVE

To evaluate the clinical response to and safety of single and repeat doses of a chimeric anti-CD4 monoclonal antibody, cM-T412, in patients with rheumatoid arthritis (RA) concomitantly treated with a stable regimen of low-dose methotrexate.

METHODS

Sixty-four patients with refractory RA, who were already receiving stable doses of methotrexate, were randomized into a multicenter, double-blind, placebo-controlled trial to receive 3 monthly treatments with either a placebo, or 5, 10, or 50 mg cM-T412, given intravenously.

RESULTS

Using > or = 50% improvement in swollen joint counts as a criterion for clinical response, 13%, 13%, 18%, and 13% of patients receiving 50, 10, or 5 mg cM-T412, or the placebo, respectively, exhibited a clinical response at 3 months of therapy. Using > or = 50% improvement in tender joint counts as a measure of clinical efficacy at 3 months, 19%, 13%, 12%, and 6% of patients receiving 50, 10, or 5 mg cM-T412, or the placebo, respectively, exhibited a clinical response. "Flu-like" symptoms (fever, chills, rigor) within 24 hours of the infusion occurred more frequently in the groups receiving 50-mg (29%) and 10-mg (31%) doses of cM-T412 than those receiving 5 mg cM-T412 (12%) or the placebo (13%). Significant CD4+ T cell depletion occurred in the 50-mg group (mean of 353 CD4+ T cells/mm3 at 6 months versus 856 CD4+ T cells/mm3 at baseline). All patients were followed up for 12 months after the final treatment; no opportunistic infectious complications occurred.

CONCLUSION

Treatment with cM-T412 in this cohort of RA patients who were also taking methotrexate was not associated with clinical efficacy or enhanced toxicity from infectious complications, despite significant peripheral CD4+ T cell depletion.

Reduction of synovial inflammation after anti-CD4 monoclonal antibody treatment in early rheumatoid arthritis

OBJECTIVE

To study the effect of chimeric anti-CD4 monoclonal antibody (MAb) therapy on synovial inflammation, in order to interpret the clinical experience with anti-CD4 treatment.

METHODS

The immunohistologic features of synovial biopsy specimens before and 4 weeks after anti-CD4 MAb (cM-T412) therapy were studied in patients with rheumatoid arthritis. The patients received intravenous doses of either placebo (n = 1) or 10 mg (n = 4), 25 mg (n = 2), or 50 mg (n = 1) of cM-T412 daily for 5 consecutive days.

RESULTS

Although the patients did not experience clinical improvement, significant decreases in the number of circulating CD4+ cells, the degree of synovial inflammatory infiltration, and the mean scores for expression of adhesion molecules were found in the 7 patients 4 weeks after receiving cM-T412. The scores for infiltration with CD4+ and other inflammatory cells were particularly reduced following treatment with either 25 mg or 50 mg cM-T412. Cytokines, such as interleukin-1 beta and tumor necrosis factor alpha, could still be detected in the synovial tissue after treatment.

CONCLUSION

The decline in the numbers of inflammatory cells and adhesion molecules in synovial tissue after CD4+ cell depletion supports the view that CD4+ T cells orchestrate local cellular infiltration. The lack of clinical effect of anti-CD4 therapy might be explained by an insufficient decrease in the number of synovial CD4+ cells and by the persistence of cytokines. Determination of whether more adequate dosing would lead to a clinical improvement must await further study.

The role of T cells in rheumatoid arthritis

The most striking arguments in favor of a T cell dependent nature of RA are the strong association of the disease with selected class II HLA haplotypes (the "shared epitope" hypothesis) and the fact that, in experimental animal models such as adjuvant arthritis, the disease can be transferred by isolated T cell lines. It is true that T cell activation at the site of inflammation is not excessive. However, there is now unequivocal evidence for focal synthesis of IL-2 and IFN-gamma in the RA synovial membrane and one may realise that a limited but specific T cell activation may be sufficient to induce or perpetuate the immune process. This same argument may explain the lack of clear TCR restriction at the sites of inflammation. Until now, no antigen has been demonstrated to initiate and/or perpetuate RA. Different antigens though have been incriminated in the pathogenesis of RA, including cartilage antigens (collagen, proteoglycans, chondrocyte antigens), heat shock proteins or exogenous (viral/bacterial) antigens. Unless one can pick up the right antigen and clone the relevant T cells, it will be very hard to directly prove a T cell-dependent nature of the disease.

A randomized, double-blind, placebo-controlled study of CD4 monoclonal antibody therapy in early rheumatoid arthritis

OBJECTIVE

To assess the efficacy of the CD4 monoclonal antibody (MAb) cM-T412 in the treatment of early rheumatoid arthritis (RA).

METHODS

Sixty patients were enrolled in a 6-week randomized, double-blind, placebo-controlled study investigating multiple dose regimens of cM-T412. Thirty patients subsequently were enrolled in a 9-month randomized, double-blind, placebo-controlled study investigating monthly single-dose administrations of cM-T412.

RESULTS

Analysis of clinical parameters revealed no changes in arthritis activity in the groups that received CD4 MAb or the placebo group, and no difference between the groups, in either in the first or the second part of the study. The number of circulating CD4+ cells decreased substantially in the patients treated with CD4 MAb.

CONCLUSION

CD4 MAb treatment of patients with early RA induced no therapeutic effect.

Pharmacokinetics of anti-ganglioside GD2 mAb 14G2a in a phase I trial in pediatric cancer patients

A phase I trial of a murine anti-ganglioside (GD2) monoclonal antibody (mAb) 14G2a was conducted in 14 neuroblastoma patients and 1 osteosarcoma patient to assess its safety, toxicity and pharmacokinetics in pediatric patients. The pharmacokinetics of mAb 14G2a were biphasic with a t alpha 1/2 of 2.8 +/- 2.8 h and a t beta 1/2 of 18.3 +/- 11.8 h. In general, t beta 1/2 was dose-dependent with a level of significance of P = 0.036, and it reached a plateau at doses of 250 mg/m2 or more. Overall the peak serum levels were dose-dependent at P < 0.001. However, they demonstrated an abrupt increase between doses of 100 mg/m2 and 250 mg/m2. The latter two suggest a saturable mechanism for mAb elimination. In addition, peak serum concentrations were observed earlier at higher mAb doses, which indicates the achievement of a steady state. The t beta 1/2 of mAb 14G2a in children appears to be shorter than in adults. Furthermore, 2 patients demonstrated a considerable decrease in t beta 1/2 following retreatment with 14G2a. This was paralleled by high human anti-(mouse Ig) antibody levels. This study represents the first comprehensive analysis of murine mAb pharmacokinetics in children and will be useful in the future design of mAb therapy.

Specific hyporesponsiveness of alloreactive peripheral T cells induced by CD4 antibodies

We investigated whether exposure of naive and in vitro pre-activated T cells to CD4 monoclonal antibodies (mAb) could induce specific hyporesponsiveness to a subsequent challenge in the absence of CD4 mAb. Unfractionated peripheral blood mononuclear cells were cultured with mitomycin-treated B cell lines as stimulator cells, in the presence or absence of CD4 mAb, then challenged with the same or unrelated stimulator cells. The kinetics of [3H] thymidine incorporation, blast transformation and CD25 expression were determined. Cells activated in primary or secondary culture in the presence of CD4 mAb demonstrated a markedly decreased response to subsequent challenge in the absence of antibody. This effect was reproduced with three different CD4 mAb of the IgG1 and IgG2a subclasses, which recognize two distinct epitopes of the CD4 molecule. Addition of recombinant interleukin-2 (rIL-2) during exposure to CD4 mAb failed to prevent the induction of specific hyporesponsiveness. Similarly, exogenous rIL-2, added together with stimulating cells, failed to restore the specific proliferative response, indicating that the mechanisms were different from those of classical anergy. The hyporesponsiveness was clonally restricted since CD4 mAb-pretreated cells developed a normal primary response to third-party stimulator cells. No increase in the percentage of apoptotic cells was observed in hyporesponsive cell populations, but selective clonal deletion cannot be excluded. The data demonstrate a delayed effect of CD4 ligation on T cell responses to a subsequent challenge.

Repeated treatment with chimeric anti-CD4 antibody in multiple sclerosis

We treated 21 multiple sclerosis patients with two to four doses of cM-T412, a chimeric monoclonal antibody against the CD4 antigen found on helper/inducer T lymphocytes. The mean number (+/- standard error) of circulating CD4 lymphocytes decreased from 888 (+/- 81) cells/mm3 at baseline to 246 (+/- 18) after treatment. At 1 year after the last treatment, the CD4 count had recovered to only 335 (+/- 32). The antibody had no effect on CD8 lymphocytes, B lymphocytes, or other leukocytes. Side effects were minimal. Despite the prolonged depletion of CD4 lymphocytes, no opportunistic infections occurred. Only 1 patient had a possible allergic reaction. Most patients were clinically stable, but a few progressed. We conclude that repeated treatment with cM-T412 is effective in reducing the number of circulating CD4 lymphocytes and has no limiting side effects.

Production of erythrocyte autoantibodies in NZB mice is inhibited by CD4 antibodies

NZB mice spontaneously develop haemolytic anaemia as the result of production of erythrocyte autoantibodies. The mechanisms leading to breakdown in tolerance to erythrocyte autoantigens are unknown. Antibodies to CD4 have been successfully used to treat several murine models of autoimmune disease. In this study we injected NZB mice with non-depleting CD4 antibodies and were able to prevent and abrogate erythrocyte autoantibody production in young (Coombs' negative) and old (Coombs' positive) mice, respectively. Our data indicate the dependency of autoantibody production on CD4+ T cells. However, withdrawal of anti-CD4 antibodies resulted in the appearance of erythrocyte autoantibodies, showing that under these conditions we were unable to re-establish tolerance to autoantigens on erythrocytes using anti-CD4 treatment.

Treatment of rheumatoid arthritis with a chimeric CD4 monoclonal antibody (cM-T412): immunopharmacological aspects and mechanisms of action

To investigate the mechanisms of action underlying the therapeutic effect of CD4 monoclonal antibody therapy in rheumatoid arthritis (RA), clinical responses were compared with several laboratory parameters. Twenty-nine RA patients received either 10 mg, 50 mg or 100 mg of cM-T412, a chimeric CD4 MoAb, for 7 days. The CD4 binding sites on circulating lymphocytes were saturated directly with cM-T412 and serum levels of unbound cM-T412 accumulated towards day 7 of treatment only in the patients treated with 50 and 100 mg. The treatment induced an instant and prolonged depression of the number of circulating CD4+ cells, similar for all dosages. Clinical improvement was observed predominantly in the patients treated with 50 or 100 mg cM-T412 daily and did not correlate with changes in counts of circulating leucocyte subsets nor with changes in serum cytokine levels. An antiglobulin response against cM-T412 developed in a majority of the patients. Side effects on the first day of treatment were correlated with an increase of serum IL-6 levels. This study indicates that a favourable clinical effect of cM-T412 administration was associated with the presence of unbound cM-T412 in the circulation of RA patients. Therefore penetration of unbound cM-T412 into the site of inflammation might determine the therapeutic effect in RA.

Treatment of rheumatoid arthritis with chimeric monoclonal antibodies to tumor necrosis factor alpha

OBJECTIVE

To evaluate the safety and efficacy of a chimeric monoclonal antibody to tumor necrosis factor alpha (TNF alpha) in the treatment of patients with rheumatoid arthritis (RA).

METHODS

Twenty patients with active RA were treated with 20 mg/kg of anti-TNF alpha in an open phase I/II trial lasting 8 weeks.

RESULTS

The treatment was well tolerated, with no serious adverse events. Significant improvements were seen in the Ritchie Articular Index, which fell from a median of 28 at study entry to a median of 6 by week 6 (P < 0.001), the swollen joint count, which fell from 18 to 5 (P < 0.001) over the same period, and in the other major clinical assessments. Serum C-reactive protein levels fell from a median of 39.5 mg/liter at study entry to 8 mg/liter at week 6 (P < 0.001), and significant decreases were also seen in serum amyloid A and interleukin-6 levels.

CONCLUSION

Treatment with anti-TNF alpha was safe and well tolerated and resulted in significant clinical and laboratory improvements. These preliminary results support the hypothesis that TNF alpha is an important regulator in RA, and suggest that it may be a useful new therapeutic target in this disease.

T cell epitopes of the major fraction of rye grass Lolium perenne (Lol p I) defined using overlapping peptides in vitro and in vivo. I. Isoallergen clone1A

One hundred and fifteen overlapping synthetic peptides spanning the entire sequence of the iso-allergen clone1A of Lol p I from rye grass Lolium perenne were synthesized by the multi-pin technique. The peptides were overlapping 12mers, offset by two residues and overlapping by 10 residues. Sets of six adjacent overlapping peptides (except pool-1, 15, 20) were pooled and were used in vitro and in vivo to map the T cell epitopes on Lol p I. Six atopics who were skin test and RAST positive to rye grass showed T cell responses to L. perenne extract (LPE) and its major fraction (Lol p I). Five out of six showed T cell responses in vitro to peptide pool-17, while five non-atopics did not respond to any of the peptide pools. By testing the individual peptides of pool-17, we have located the T cell epitope on Lol p I. Interestingly, when we tested pool-17 and its single peptides in vivo by intradermal skin testing we found in one patient a typical DTH after 24-48 h to pool-17 and its peptides (peptides 3 and 4) which exactly matched the in vitro responses. By defining the T cell epitopes in this way a greater understanding of the allergic response to pollen will be obtained, and a more effective and less dangerous vaccine may be possible for treating patients with hay fever.

In vivo treatment with a monoclonal chimeric anti-CD4 antibody results in prolonged depletion of circulating CD4+ cells in chimpanzees

Chimeric M-T412 (cM-T412), an anti-CD4 antibody, was tolerated in chimpanzees at a dosage of 5 mg/kg per day for up to 7 consecutive days, or 5 mg/kg per dose, twice weekly for 4 weeks. All cM-T412-treated chimpanzees showed a prolonged CD4-cell depression. Weak chimpanzee antibody responses to chimeric M-T412 were observed. One of the chimpanzees on the biweekly dosage regimen exhibited a hypersensitivity reaction immediately after receiving its seventh dose. Following supportive treatment, the animal recovered and remained asymptomatic during the non-treatment observation period. The hypersensitivity reaction was not an unexpected response considering the animal received repeated intermittent i.v. administration of a foreign protein. This animal also showed a chimpanzee antibody response to chimeric M-T412 after the seventh dose. Chimeric M-T412 also induced an anti-cM-T412 response in some of the other animals. The level of this response was lower than the anti-mouse responses observed in animals treated with murine anti-CD4. Moreover, the anti-cM-T412 response was mainly directed to idiotypic determinants. The decrease in CD4+ cells observed for all chimeric M-T412-treated chimpanzees is an expected effect of the anti-CD4 antibody. The duration of this CD4+ cell decrease is, however, much longer than observed for other CD4-specific MoAbs described. No selective loss of either memory or naive CD4+ cells was observed after either the single, 7-day or twice-weekly treatments. The CD4+ cell depression was reversible, although individual variation in time to recovery was observed. Therefore, cM-T412 could be a good candidate for clinical use in autoimmune conditions.

Immunosuppressive therapy of autoimmune diseases

Cyclosporin A, corticosteroids and cyclophosphamide show a remarkable efficacy in a large number of autoimmune diseases. However, their effect is dependent on continuous drug administration with potential risks of drug toxicity and over immunosuppression. Results recently obtained in animal models, particularly with anti-CD3 and anti-CD4 monoclonal antibodies, indicate that reestablishment of tolerance to self antigens is a feasible goal.

Control of immune-mediated disease of the central nervous system with monoclonal (CD4-specific) antibodies

Chronic relapsing experimental allergic encephalomyelitis (CREAE) was induced in Biozzi AB/H (H-2dq1) mice by active sensitization with spinal cord antigens. A single i.p. injection of CD8-depleting (YTS169.4) monoclonal antibody (mAb) failed to affect the clinical course of CREAE when administered prior to and during the onset of both the initial clinical and subsequent relapse phase of the disease. By contrast similar treatment with both CD4-depleting (YTS191.1) or CD4-blocking/non-depleting (YTS177.9) mAb significantly inhibited disease progression. Treatment shortly before the anticipated onset of clinical EAE prevented the subsequent development of disease, although disease could be provoked following antigen-rechallenge. In contrast, treatment with these antibodies during post-acute remission phase mainly served to delay the incidence of relapse. This suggests that, unless tolerance can be re-induced, treatment of ongoing neuroimmunological disease will require 'pulse' therapy and thus potentiate the problems of long-term immunosuppresion. Despite the findings that CD4-specific antibodies can rapidly reverse overt clinical disease shortly after the onset of disease exacerbation, once neurological dysfunction becomes established anti-CD4 treatment fails to improve the animals clinically, possibly due to the inability to rapidly reverse established demyelination. Although this study does not exclude the potential central action of the injected mAb, the failure to significantly dissociate therapeutic benefit between mAb administered directly into the CNS and that given systemically suggests that a major action of these agents is probably by selectively removing T cells in the peripheral T cell pool.

Selective immunosuppression

Experimental models of autoimmune diseases have demonstrated that such disease can be prevented or treated by selectively interfering with activation of any of these cell types: antigen-presenting cells, autoreactive T cells and regulatory T cells. Luciano Adorini and colleagues discuss these approaches to selective immunosuppression and examine how similar strategies may become applicable to the treatment of human autoimmune diseases.

Selective immunosuppression

Experimental models of autoimmune diseases have demonstrated that such disease can be prevented or treated by selectively interfering with activation of any of these cell types: antigen-presenting cells, autoreactive T cells and regulatory T cells. Luciano Adorini and colleagues discuss these approaches to selective immunosuppression and examine how similar strategies may become applicable to the treatment of human autoimmune diseases.

Effects of administration of an anti-CD5 plus immunoconjugate in rheumatoid arthritis. Results of two phase II studies. The CD5 Plus Rheumatoid Arthritis Investigators Group

OBJECTIVE

To evaluate the safety and activity of an immunoconjugate of ricin A chain and anti-CD5 monoclonal antibody (anti-CD5 IC), with and without concomitant methotrexate and/or azathioprine, in the treatment of rheumatoid arthritis (RA).

METHODS

Seventy-nine patients with active RA were enrolled in 2 prospective open-label protocols.

RESULTS

Using composite criteria, response rates were 50-68% at 1 month and 22-25% at 6 months. Transient depletion of CD3/CD5 T cells was observed on days 2 and 5 of treatment, with reconstitution on day 15 or day 29. Treatment-associated adverse effects were common but resolved rapidly without sequelae.

CONCLUSION

These findings suggest activity of anti-CD5 IC in active RA and warrant confirmation in a multicenter randomized study (currently underway).

Immunosuppressive therapy of autoimmune diseases

Ciclosporin and cyclophosphamide show a remarkable efficacy in most autoimmune diseases. However, their effect is dependent on continuous drug administration with risks of drug toxicity and over immunosuppression. Results recently obtained in animal models, discussed here by Jean François Bach particularly with anti-CD3 and anti-CD4 monoclonal antibodies, indicate that reestablishment of tolerance to self antigens is a feasible goal.

Internalization and degradation of anti-CD4 monoclonal antibodies bound to human peripheral blood lymphocytes

Treatment of patients with anti-CD4 mAbs induces both functional alterations of CD4+ cells and depletion of circulating CD4+ lymphocytes. Some of these effects depend on the amount of mAb molecules bound per CD4+ cell and on the properties of the Fc part of the mAb (isotype specificity). We have investigated the fate of anti-CD4 monoclonal antibodies (mAbs) after their interaction with CD4 protein on the surface of peripheral blood lymphocytes (PBL). We used seven anti-CD4 mAbs whose epitope specificity, equilibrium constant and kinetics of binding are reported. Lymphocytes were saturated with anti-CD4 mAbs either at +4 degrees C or 37 degrees C then washed and incubated in antibody-free medium. At different time intervals cells were processed for analysis. By indirect immunofluorescence, it was shown that the amount of surface-bound mAb decreased rapidly when cells were incubated at 37 degrees C, but not at 4 degrees C. With 125I-mAbs, we demonstrate that there was a rapid internalization of the molecules followed by the re-expression on the cell surface of a part of initially bound mAbs and by the release of partially degraded antibody in the cell supernatant. In the presence of sodium azide (10 mM) only a slow dissociation of intact antibody occurred, without internalization. The radioactive material eluted in the 100-200 kDa zone from supernatants was only partly adsorbed on protein A and hardly on CD4+ cells, indicating that alterations of the Fc region and loss of antigen binding activity, possibly by formation of CD4-anti-CD4 complexes, had occurred during the process of internalization and release into the extracellular medium. These data may be important to consider for adjusting the dosage of anti-CD4 mAbs to be administered.

Use of a chimeric monoclonal anti-CD4 antibody in patients with refractory rheumatoid arthritis

OBJECTIVES

To evaluate the safety, immunogenicity, and biologic effects of chimeric monoclonal anti-CD4 (cM-T412) in patients with refractory rheumatoid arthritis (RA), and to obtain preliminary data on the clinical response to this treatment.

METHODS

Twenty-five patients with active refractory RA were treated with incremental doses (10 to 700 mg) of cM-T412 in an open-label, escalating-dose phase I trial.

RESULTS

Infusion with cM-T412 was followed by an immediate, rapid decline in CD4+ T cells. The level of circulating CD4+ T cells remained depressed in most patients even at 6 months posttreatment. Following antibody infusion, proliferative responses of peripheral blood lymphocytes to mitogens and antigens were determined; mitogen and antigen responses were decreased compared with pretreatment responses. Mitogen responses tended to return to baseline values more rapidly than did responses to antigen. Adverse events included fever (19 patients), which was associated with myalgias, malaise, and asymptomatic hypotension; these symptoms were self-limited and appeared to correlate with transient elevations in interleukin-6. No significant human antibody response to the cM-T412 variable region was detected; only 2 patients developed transiently low levels of antibodies reactive with cM-T412. Significant clinical improvement, defined as > or = 50% decrease in tender joint counts compared with baseline, was noted in 43% of patients at 5 weeks and 33% at 6 months following cM-T412 infusion.

CONCLUSIONS

Treatment of refractory RA with cM-T412 appears to be safe and is associated with sustained decreases in circulating CD4+ T cell counts and depressed in vitro T cell responses. No significant human antichimeric antibody response was detected. Nonblinded assessment of clinical end points suggests that treatment with cM-T412 may have beneficial effects in these patients with refractory RA. A double-blind clinical trial is warranted to determine its clinical efficacy in treating RA.