Rigel sees clear forward path for fostamatinib but will drop R333

Clinical-stage US drug developer Rigel Pharmaceuticals (Nasdaq: RIGL) has announced mixed updates on two of its pipeline products: R333, a topical dermatological JAK/SYK inhibitor, and fostamatinib, an oral SYK inhibitor, both of which were seen as promising for the company’s future.

This news follows recent disappointing clinical results with the company’s asthma drug candidate R343 (The Pharma Letter August 27), and caused the firm’s shares to fall 2.3% to $3.46 in mid-afternoon trading yesterday (October 24).

R333 update

Rigel that R333, which was being evaluated as a potential therapeutic for active skin lesions in patients with discoid lupus erythematosus (DLE), did not meet the primary endpoint in a recently completed Phase II clinical study. The primary endpoint was the proportion of patients who achieved at least a 50% decrease from baseline in the total combined Erythema and Scaling score of all treated lesions at Week 4. R333 was shown to be relatively safe and well tolerated. However, in light of these overall findings, Rigel has decided not to pursue this indication further with R333.