Analyst Sees Deteriorated Treatment Effect Of Blueprint's Much Awaited Mastocytosis Data

Earlier today, Blueprint Medicines Corporation BPMC released the long-awaited pivotal PIONEER dataset in Indolent Systemic Mastocytosis (ISM).
The topline data indicates that the trial met all primary and key secondary endpoints with statistical significance and that there were no intracranial bleeds.
SVB Leerink thinks that though these data are approvable, they represent a deterioration in the absolute improvement in the symptom score (TSS), which was 15.6 points in this trial versus 19.7 in Phase 1.
Conversely, the control arm of best supportive care (BSC) showed a larger reduction in TSS from a baseline of 9.2 points versus 3.2 in Phase 1.
This represents a meaningful deterioration in the treatment effect for Ayvakit over BSC, now 6.4 from 16.5, a key metric that clinicians and payors are likely to weigh, given the anticipated cost.
The analyst believes that the data will further magnify the commercial debate, as investors question the size of the addressable ISM population for a chronically used therapy with a limited treatment effect that could cost over $350,000 per year.
Price Action: BPMC shares are down 7.19% at $63.67 on the last check Wednesday.

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