Plexxikon has initiated dosing in the first of two Phase I clinical trials to evaluate PLX5622, an oral and highly selective FMS inhibitor targeted for the treatment of rheumatoid arthritis.

The first Phase I clinical trial is a single-ascending dose study in 32 healthy volunteers, while the second is a multiple-ascending dose study in 32 rheumatoid arthritis patients.

Dosing in the rheumatoid arthritis will begin once the first cohort of healthy volunteers has been cleared for safety.

Preclinical studies have demonstrated that PLX5622 reduces inflammation and cartilage damage, and prevents bone resorption.

PLX5622 also significantly improved grip strength and clinical scores, as well as improved knee joint range-of-motion scores.

Rheumatoid arthritis is a chronic disease characterised by pain, stiffness and swelling, primarily in the joints. It is thought to affect more than 1.3 million people in the US.