On a roll, Rigel flags a positive PhII for its lead, late-stage drug fostamatinib

Rigel has been having one of those weeks its investors have been dreaming of for years.

First the biotech $RIGL, which has had some mixed news to report on late-stage studies of their drug fostamatinib, helped inspire some confidence on Monday by announcing that the FDA doesn’t need to have a panel review ahead of its PDUFA date.

Score one for the optimists who read that as a tacit acceptance, although there are absolutely no guarantees.

The second bounce on Tuesday followed Rigel’s announcement that the first leg of a two-part, open-label Phase II for warm antibody AIHA achieved the first snapshot of efficacy it was was looking for: a hemoglobin level of greater than 10 g/dl and at least a 2 g/dl increase from baseline among 17 patients.

Score two for the optimists willing to buy into a small, mid-stage study without a control group. Shares, which gyrated up 32% yesterday, continued to rise Tuesday morning.

Warm antibody AIHA is the most common form of rare cases of autoimmune hemolytic anemia, a blood disorder where the immune system produces antibodies that destroy red blood cells.

A year ago the South San Francisco-based biotech’s share price went on a roller coaster ride with a positive but unimpressive 18% response rate for immune thrombocytopenia patients who achieved a stable platelet response. That was exactly the same rate seen in the second Phase III, except that one patient on a placebo also achieved a stable platelet response, and that scuttled any shot at hitting the primary endpoint. For analysts who had been looking for a response rate at least in the low 20s with clear signs of efficacy, the stumble did not play well.

Rigel has been pursuing studies for fostamatinib for years, with decidedly mixed results. But it’s all coming down to the wire now.

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Research Scientist - Immunology
Recursion Pharmaceuticals Salt Lake City, UT
Director of Operations
Atlas Venture Cambridge, MA

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