EHA 2026 | Updates with bezuclastinib in non-advanced and advanced systemic mastocytosis: SUMMIT & APEX trials

So it’s an exciting EHA because you’ve got data that’s mature from the use of bezuclastinib in both non-advanced and advanced SM as you’ve stated. So the SUMMIT trial is sharing data on those patients with non-advanced disease, so indolent and some smouldering SSM patients. The data using bezuclastinib at a dose of 100 milligrams once daily versus placebo, 2 to 1 randomization, about 119 patients in the treatment arm and 60 patients in the non-treatment arm, met its primary objective, which is literally based on a symptom assessment score improvement. So a symptom assessment called MSD2 was used. The patients who were on the drug had a significant improvement in their symptom assessment score of an improvement of 24% versus 15% with placebo, which is great. Also additional data showed that looking at the pathology of those patients who had bone marrow samples, that there’s a correlation between the decrease in disease burden measured by the tryptase, bone marrow mast cell burden, as well as the CKIT-VAF, correlates with an improvement in symptom burden. So it’s quite nice to have that correlation to say that there’s an improvement. So really great outcomes for the non-advanced disease for SM bezuclastinib at 100 milligrams once daily. 

Shifting to the advanced, the APEX trial, which is going to be presented as an oral presentation by Dan Deangelo on Saturday, sharing the data. 68 patients total, bezuclastinib part two at a dose of 150 milligrams once daily. For those patients with advanced disease, who had poor prognosis. Again, has shown that the overall response rate on those patients is up to 66%, and that’s achieving a clinical remission, partial remission, and a clinical improvement. And if we just use, and that’s by the MIWG criteria, complex criteria, if we just use pure pathological response, that’s tryptase levels, mast cell disease burden, and CKIT-VAF improvement, it’s up to 81%. So we’re showing deep responses with the potent drug, bezuclastinib at 150 milligrams once daily, reasonably well tolerated, no intracranial bleeds seen, degree of myelosuppression does not cause significant thrombocytopenia, and slightly milder derangements of liver function tests which improve over time. So very good that there’s possibly another potent CKIT inhibitor for those patients with advanced and non-advanced diseases in the horizon.

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