Although multiple treatment options are currently available for people suffering from rheumatoid arthritis (RA), there will always remain room for effective new therapies.

That is due to the high variability of response rates to the leading biologics that are now used for treatment of the disease. Janssen Biologics (Ireland), part of the Janssen Pharmaceutical Cos. of Johnson & Johnson, and GlaxoSmithKline plc are co-developing sirukumab, an investigational human monoclonal IgG1 kappa antibody, which they hope will become a future treatment option.

Sirukumab, a human anti-interleukin (IL)-6 monoclonal antibody has just been entered into a Phase III program for the treatment of adults with moderately to severely active RA. IL-6 is a promising target with research indicating that its overproduction plays a significant role in the pathology of RA.

The companies said two studies will be conducted. One trial, designated SIRROUND-T, will be a randomized, double-blind, placebo-controlled, parallel group study of sirukumab administered subcutaneously in subjects with active RA despite antitumor necrosis factor (TNF)-alpha therapy.

The primary objective will be to assess the efficacy of sirukumab as measured by the reduction of the signs and symptoms of RA in subjects with active RA who are refractory or intolerant to anti-TNF-alpha agents such as Humira (adalimumab, Abbott) and Enbrel (etanercept, Amgen Inc.),

In the second SIRROUND-D trial, sirukumab will be dosed in subjects with active RA despite disease modifying antirheumatic drug (DMARD) therapy.

According to information on clinicaltrials.gov, the current estimated completion dates for the study in active patients despite anti-TNF-alpha therapy is projected to be January 2016, and the study in active RA patients despite DMARD therapy is scheduled to be completed in November 2016.

The Phase III program follows successful Phase II results for sirukumab, reported at the American College of Rheumatology meeting in November 2011.

The antibody significantly improved rheumatoid arthritis signs and symptoms, as measured by the American College of Rheumatology 50 (ACR50) response at week 12, the primary endpoint. Treatment with sirukumab was generally well tolerated. (See BioWorld Today, Nov. 8, 2011 .)

Janssen and GSK entered into a co-development and co-commercialization license agreement for sirukumab in RA In December .

RA, an autoimmune disease that causes inflammation in the joints, affects an estimated 1.3 million people in the U.S., or 1 percent of the population, according to the Arthritis Foundation.

The overall market for disease sufferers worldwide is significant and has been estimated at more than $13 billion.