Rigel Pharmaceuticals: First patient enrolled in Phase 1b study of R289

Rigel Pharmaceuticals (RIGL) announced the first patient has been enrolled in the dose expansion phase of the ongoing Phase 1b study of R2891 in patients with relapsed or refractory lower-risk myelodysplastic syndrome. R289 is Rigel’s potent and selective dual inhibitor of interleukin receptor-associated kinases 1 and 4. Enrollment in the dose escalation phase of the study was completed in July 2025, and the company expects to share updated data from the study later this year.