"New, effective therapeutic options in RA are greatly needed since current treatments have potentially significant limitations," said Elliott Grossbard, senior vice president of medical development at Rigel.
"We are pursuing R788 in autoimmune diseases such as RA and ITP because it has been shown to be a potent and selective inhibitor of syk kinase, which may play a key role in autoimmune diseases," he added.
Preliminary data from a Phase I double-blind, placebo controlled trial to investigate the safety and pharmacokinetics of R788, an oral syk kinase inhibitor, in combination with methotrexate in rheumatoid arthritis (RA) patients, proved encouraging as scientists determined the exact role of the drug compound.
R788 is a novel, oral syk kinase inhibitor that blocks the activation of mast cells, macrophages and B cells that promote swelling and an inflammatory response. It is being developed initially to treat RA.
Phase I trial results have demonstrated that R788 is well tolerated and showed good pharmaceutical properties. Earlier Phase I studies generated pharmacokinetic/pharmacodynamic data establishing a strong correlation between drug plasma levels and the inhibition of the drug target.
In preclinical studies, Rigel's compound diminished the swelling and tissue destruction associated with RA. In addition, in a murine model of ITP, the drug increased platelet counts.
The company also announced plans to initiate separate clinical efficacy studies with R788, in RA and in Immune Thrombocytopenic Purpura (ITP), in the second half of 2006.
Approximately 2.1 million people in the US suffer from RA and the worldwide market for innovative RA drugs is projected to reach $10 billion (€8.4bn) by 2008.
RA is a chronic inflammatory disease that affects multiple tissues, but typically produces its most pronounced symptoms in the joints.
It is a progressive and debilitating disease and ultimately the chronic inflammation of joints leads to the destruction of the soft tissue and erosion of the articular surfaces of the bone.
Some RA patients currently receive multiple drugs depending on the extent and aggressiveness of the disease.
Most RA patients require some form of DMARD - including methotrexate, an anti-cancer agent, or TNF-blocking agents such as Enbrel.
The TNF-blocking agents only inhibit the inflammatory mediator TNF, and are all delivered via injection. Rigel believes that there is a significant opportunity for an oral DMARD that can be used earlier in the course of the disease, preventing its progression prior to major bone and cartilage destruction.