Potential biologic agents for treating rheumatoid arthritis

Making smart investment decisions in clinical research

A recent trial in rheumatoid arthritis found an inexpensive, but infrequently used, combination of therapies is neither inferior nor less safe than an expensive biologic drug. If the trial had been conducted over 10 years ago, arguably 100’s of millions of dollars since spent on biologics could have been released to other, more effective treatments. Given the ever increasing number of trials proposed, this commentary uses the trial as an example to challenge payers and research funders to make smarter investments in clinical research to save potential future costs.

Trial registration: NCT00405275, registered 29 November 2006

Anakinra: an inhibitor of IL-1 for the treatment of rheumatoid arthritis

Anakinra (Amgen, Inc.) is a specific receptor antagonist of IL-1 that differs from naturally occurring IL-1 receptor antagonist by the presence of a methionine group. Anakinra has been shown to be of benefit in patients with active rheumatoid arthritis, either when given alone or in combination with methotrexate, as assessed by improvement in clinical signs and symptoms, decreased radiographic progression and improvement in patient function, pain and fatigue, although it appears to be effective in fewer patients than anti-TNF agents. It has a favourable safety profile as demonstrated in clinical trials. The physician and patient must be cognizant of serious infectious episodes. Many of the rare side effects seen with TNF blockers, such as tuberculosis, other opportunistic infections, worsening of congestive heart failure and the development of demyelinating disease, have not been seen in patients treated with anakinra. Anakinra should not be given in combination with anti-TNF agents.

Regulation of c-Jun phosphorylation by the I kappa B kinase-epsilon complex in fibroblast-like synoviocytes

Rheumatoid arthritis (RA) causes a symmetric, inflammatory polyarthritis that results in joint destruction and significant disability. Signaling pathways that regulate the production of cytokines and destructive enzymes have been implicated in its pathogenesis and represent potential therapeutic targets. The IkappaB kinase (IKK)-related kinase, IKKepsilon/IKKi, which plays a pivotal role in regulating antiviral gene transcription, is constitutively expressed by cultured fibroblast-like synoviocytes (FLS) and could participate in the pathogenesis of RA. In the current studies we demonstrate that IKKepsilon protein is expressed in RA and osteoarthritis synovium and that the protein is found primarily in the synovial intimal lining. Functional studies in cultured FLS showed that IKKepsilon kinase activity is rapidly induced by cytokines, although IkappaB phosphorylation is significantly less compared with IKK2. Because NF-kappaB activation is similar in wild-type and IKKepsilon knockout murine FLS, studies were performed to identify an alternative substrate for IKKepsilon. Interestingly, c-Jun is a more efficient substrate for IKKepsilon immunocomplexes in human FLS and this activity appears to be independent of JNK. The functional relevance of IKKepsilon was examined using murine IKKepsilon(-/-) cultured FLS. IL-1-, TNF-alpha-, and LPS-mediated induction of matrix metalloproteinases, MMP3 and MMP13, is significantly decreased in the IKKepsilon(-/-) cells. These data suggest a novel role for the IKKepsilon complex in synovial inflammation, extracellular matrix destruction, and activation of the viral program and innate immune response in RA.

Rheumatoid arthritis: regulation of synovial inflammation

Rheumatoid arthritis (RA) is a systemic, inflammatory autoimmune disorder that presents as a symmetric polyarthritis associated with swelling and pain in multiple joints, often initially occurring in the joints of the hands and feet. Articular inflammation causes activation and proliferation of the synovial lining, expression of inflammatory cytokines, chemokine-mediated recruitment of additional inflammatory cells, as well as B cell activation with autoantibody production. A vicious cycle of altered cytokine and signal transduction pathways and inhibition of programmed cell death contribute to synoviocyte and osteoclast mediated cartilage and bone destruction. A combination of targeted interventions at various stages in the pathogenesis of RA will likely be required to control symptoms in certain patients with this complex and potentially disabling disease. The regulation of rheumatoid synovial inflammation will be reviewed, followed by a brief summary of the therapeutic implications of these advances, including strategies targeting key cytokines, signal transduction molecules, co-stimulatory molecules, B cells, chemokines, and adhesion molecules.

Splenectomy attenuates streptococcal cell wall-induced arthritis and alters leukocyte activation

OBJECTIVE

To investigate the role of the spleen in the pathogenesis of streptococcal cell wall (SCW)-induced arthritis and determine the impact of splenectomy on monocytes and T cells involved in the arthritis.

METHODS

Female Lewis rats were separated into 4 groups: 1) saline-injected, sham-operated; 2) saline-injected, splenectomized; 3) peptidoglycan-polysaccharide (PG-PS)-injected, sham-operated; and 4) PG-PS-injected, splenectomized. After a 10-day recovery period, rats received a single intraperitoneal injection of saline or PG-PS (25 microg rhamnose/gm body weight). We evaluated the effect of splenectomy on joint inflammation, histopathology, leukocyte subtypes in blood and lymph nodes, cytokines, and cell surface expression of CD44 and CD45RC in the chronic phase of the disease (day 28).

RESULTS

Splenectomy dramatically decreased chronic joint inflammation and histopathologic damage as well as altered cell types in lymph nodes and peripheral blood, as analyzed by flow cytometry. Nitric oxide (NO) production, levels of interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha, and a biomarker of Th1 cell predominance correlated with the level of joint inflammation. Surprisingly, in splenectomized animals, increased expression of adhesion molecules thought to track T cells to inflamed tissue were observed in lymph nodes.

CONCLUSION

The result of splenectomy was attenuation of SCW-induced arthritis and changes in mediators of inflammation, including T cell subsets, proinflammatory cytokines, and NO production. Splenectomy may remove an important antigen reservoir and alter immune cell activation in the SCW-induced arthritis model.

Abandoned therapies and unpublished trials in rheumatoid arthritis

The capability of selectively targeting pathogenic elements of disease with biologic therapies has created a new therapeutic repertoire. Although a substantial number of biologic agents have been developed for treatment of rheumatoid arthritis, few have been approved for use. Most of the agents have failed to reach the approval stage because of inadequate clinical benefit. Despite this, studies of these agents have provided extremely valuable lessons in study design, immunobiology, pharmacodynamic evaluation, and the utility of animal models in the development of biologic agents. These insights have laid the groundwork for future development of other novel therapeutic agents in the treatment of rheumatoid arthritis.

New therapies: plasmapheresis, intravenous immunoglobulin, and monoclonal antibodies

Rheumatologic emergencies may pose a serious threat to life, and the treatment of patients with these illnesses continues to be challenging. In the last decade extensive animal and human research has led to development of new therapies. Considerable progress has been made in the therapy for RA. Newly developed biologic therapies have shown promising results in clinical studies, and two agents have already been approved by the FDA. These drugs are currently available for therapy and are under close postmarketing scrutiny to assess long-term efficacy and safety. Similar therapies are under investigation for SLE. Plasmapheresis, once used for many diseases, is now restricted mostly to conditions for which its use has been shown to be beneficial in randomized, controlled studies. Immunoadsorption is used to target specific disease-producing pathogens for removal during extracorporeal therapy. Evidence is accumulating for the use of IVIGs in several immune-mediated conditions. The outlook for some emergencies continues be grim, however, and various therapies are used based on evidence from anecdotal case reports and case series. The new therapies are relatively safe, but careful monitoring is needed, because there is potential for serious adverse events.

Biological modifier therapy for the treatment of rheumatoid arthritis

The recent elucidation of pathogenic processes involving tumor necrosis factor alpha and interleukin-1beta in the pathogenesis and persistence of rheumatoid arthritis led to the development of biological modifier agents that have had significant impact on disease severity and progression. These agents--etanercept, infliximab, and anakinra--produce a dramatic reduction in RA disease activity with relatively low toxicity compared with currently available disease-modifying antirheumatic drugs. The main prohibition to their broader utilization is cost. The success of these agents underscores the investigative approaches to the pathogenesis of RA and the appropriate design of pharmaceutical agents to target specific proinflammatory molecules.

The pathogenesis of rheumatoid arthritis: a guide to therapy

The cause of rheumatoid arthritis (RA) is unknown; however, extensive research has yielded great insight into its pathogenesis. Lymphocytes play a significant role, but a lesser role in the perpetuation of late disease. The rheumatoid synovium is composed primarily of fibroblasts and monocytes that produce inflammatory cytokines, of which interleukin-1 and tumor necrosis factor are of key importance. Potential regulatory mechanisms balancing the effects of these cytokines are inadequate to prevent joint damage and subsequent disability. These cytokines seem responsible for stimulating destructive processes in the joint via induction of prostaglandins, angiogenesis, chemokines, adhesion molecules, osteoclastogenesis, and matrix metalloproteinases. This review discusses recent research findings in the immunopathogenesis of RA with respect to potential targets for therapy.