Fostamatinib produces responses in ITP

Role of concomitant therapy

The researchers noted that 2 of the 18 patients with a stable platelet response were on concomitant treatment. Both were on steroids, one of them for 62 days before the first dose of fostamatinib and the other for 14 years.

Four of the 43 patients with an overall platelet response were on concomitant therapy. Three were on steroids—for 62 days, 67 days, and 14 years prior to first dose of fostamatinib—and 1 was on azathioprine—for 197 days prior to the first dose of fostamatinib.

The researchers said the effects of these therapies probably would have been evident prior to study entry, so they aren’t likely to have influenced the results.

Safety

In both trials, the rate of AEs was 83% in the fostamatinib recipients (32% mild, 35% moderate, and 16% severe AEs) and 75% in the placebo recipients (42% mild, 19% moderate, and 15% severe AEs.).

AEs occurring in at least 5% of patients (in the fostamatinib and placebo arms, respectively) included diarrhea (31% vs 15%), hypertension (28% vs 13%), nausea (19% vs 8%), dizziness (11% vs 8%), ALT increase (11% vs 0%), AST increase (9% vs 0%), respiratory infection (11% vs 6%), rash (9% vs 2%), abdominal pain (6% vs 2%), fatigue (6% vs 2%), chest pain (6% vs 2%), and neutropenia (6% vs 0%).

Moderate or severe bleeding-related AEs occurred in 9% of patients who had an overall response to fostamatinib and 16% of patients on placebo.

Serious AEs considered related to study drug occurred in 4 patients on fostamatinib and 1 patient on placebo. The placebo recipient experienced a bleeding event, and the fostamatinib-related events were consistent with the AE profile of the drug (hypertension, diarrhea, etc.), according to Rigel Pharmaceuticals.

There were 2 deaths. One placebo recipient died of probable sepsis 19 days after withdrawing from the study due to epistaxis. One fostamatinib recipient developed plasma cell myeloma, stopped treatment on day 19, and died 71 days later.