Safety of Tofacitinib, an Oral Janus Kinase Inhibitor, in Systemic Lupus Erythematosus; a Phase Ib Clinical Trial and Associated Mechanistic Studies

BACKGROUND:

Systemic Lupus Erythematosus (SLE) is an autoimmune disease with variegated clinical presentation resulting from involvement of multiple biologic pathways. The pathways that lead to loss of tolerance in SLE include: multiple autoreactive cell types (B, T, dendritic, Th17 and regulatory T cells) and abnormal cytokine milieus, genetic factors, environmental and hormonal influences, all of which can influence cell differentiation patterns and reset tolerance checkpoints. In addition, recent studies indicate a putative role for neutrophils in lupus pathogenesis and associated end-organ damage. Currently available therapeutics are frequently inadequate to treat disease flares and simultaneously expose patients to potentially serious toxicities. Further, premature cardiovascular disease not explained by the Framingham risk equation has become one of the most important causes of morbidity and mortality in this patient population. To date, no treatment used in lupus appears to significantly decrease cardiovascular risk. Identifying a drug that has immunomodulatory effects and is also vasculoprotective is an unmet need in this disease.

Tofacitinib is an orally administered Janus kinase (JAK) inhibitor that has recently been approved by the Food and Drug Administration for the treatment of moderate to severe rheumatoid arthritis (RA).

The JAKs are a family of intracellular enzymes (JAK1, 2 and 3 and TYK2) that mediate signaling via a broad range of cytokine receptors. Targeting JAKs is an attractive therapeutic possibility for SLE for many reasons. Many of the inflammatory cytokines implicated in the pathogenesis of SLE signal via the JAK-STAT pathways. JAK inhibitors have been found to have efficacy in various murine models of lupus. Mice treated with a JAK2 inhibitor exhibited reduced serum levels of IL-6, and IL-17 along with reduced numbers of long-lived autoantibody producing plasma cells in the spleen and bone marrow. Furthermore, we have found that administration of tofacitinib reduced serum levels of ANA, IL-6, and IFN-gamma; and ameliorated glomerulonephritis (unpublished data).

This study therefore represents an innovative investigative measure of the safety and efficacy of JAK inhibition in SLE that is predicted by genetic predisposition. We will also investigate effects of tofacitinib on vascular function in SLE subjects and identify biomarkers that may be useful as endpoints in future studies.