Mast Therapeutics in stormy waters after PhIII flop; program, job cuts expected

Mast was down by more than 80% premarket this morning on the news that its late-stage sickle cell disease candidate vepoloxamer (MST-188) failed to beat placebo, as the biotech looks to cut the program, and its staff.

In the so-called Epic Phase III trial, top-line results showed vepoloxamer missed its primary endpoint after not hitting a statistically significant reduction in the mean duration vaso-occlusive crisis (VOC) in sickle cell patients (82 hours in the vepoloxamer group compared to 78 hours in the placebo group).

In another setback, Epic also failed to show statistically significant differences between treatment groups across the San Diego biotech’s two secondary efficacy endpoints: rate of re-hospitalization for VOC and the occurrence of acute chest syndrome.


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 “We are exceedingly disappointed with these top-line results. While clearly not the outcome we wanted, we believe the insights and data from the largest placebo-controlled clinical trial ever completed in sickle cell disease will substantially advance the understanding of vaso-occlusive crisis and the still maturing clinical science necessary to support the development of new therapeutics for this debilitating disease,” said Brian Culley, Mast’s CEO.

He also said the company will likely can the program, adding: “Based on the data we've seen to date, we expect we will terminate all clinical development of vepoloxamer.”

He said the biotech would now “evaluate our options,” but warned that cuts would be coming. “We intend to significantly and immediately reduce our operating expenses and continue our efforts with AIR001, our lead asset in heart failure with preserved ejection fraction, which currently is the subject of a 100-patient Phase II study expected to complete enrollment by the end of 2017.”

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