New Essential Thrombocythemia Treatment Appears to Address Underlying Disease
Key claim: In an early-phase ET cohort of 49 patients, INCA033989 achieved 66% complete response in platelet normalization and reduced mutant CALR variant allele frequency in 89% of evaluable patients, suggesting disease-modifying potential.
Abstract
In an ET cohort of 49 patients, 66% achieved complete response in platelet count normalization, with 89% of evaluable patients showing reduction in mutCALR VAR from baseline, with 21% achieving 50% or more reduction. The myelofibrosis cohort study is still enrolling, with top-line results expected around the end of the year.
Why this matters
This is the first ET-specific clinical efficacy readout for INCA033989, moving CALR-directed therapy from MF proof-of-concept into the subtype where CALR mutations are most actionable as a disease-modifying target. The combination of hematologic normalization with deep mutant-allele reduction is unusual in ET, where current cytoreduction (HU, anagrelide, even pegIFNα in CALR-mutated patients) rarely achieves molecular response — positioning INCA033989 as a candidate genotype-stratified therapy that could reshape ET natural history for the ~25–30% CALR-mutated subset.