Blueprint’s BLU-285 mastocytosis ASH data promising, but KIT mutation-targeting knife may cut both ways – experts

19 Dec 2017

Blueprint Medicines' (NASDAQ:BPMC) Phase I data for avapritinib in advanced systemic mastocytosis (SM) is praiseworthy but its advantageous target specificity could also engender resistance mutations down the line, experts said on the sidelines of the 2017 ASH meeting.

While the drug is seen as competitive to Novartis’ (VTX:NOVN) approved Rydapt (midostaurin), avapritinib’s greater specificity to KIT mutations – the driver mutation in SM – could also be a disadvantage with the resistance mutations having the potential to render the drug ineffective, experts said.

One expert said that feature could give Rydapt a competitive edge, being less likely to create resistance mutations, though others were less convinced about Rydapt’s “dirty” or multikinase inhibitor approach being a solid advantage. Rydapt, approved on 28 April for SM as well as frontline FLT3-positive acute myeloid leukemia (AML), is expected to have YE27 sales of USD 565m, according to analysts.

Analysts heralded the drug’s 72% overall response rate (ORR) and 100% disease control rate (DCR), noting that the Phase I data shows reductions in mast cell burden that appear comparatively better than Rydapt, according to reports. Blueprint’s stock rose 26% in premarket trading following the data release.

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