Zavabresib Earns FDA Orphan Drug Designation in Myelofibrosis
Key claim: Zavabresib (OPN-2853), a selective BET inhibitor, received FDA orphan drug designation for myelofibrosis and demonstrated durable spleen reduction when combined with ruxolitinib in patients with inadequate ruxolitinib response.
Abstract
Regulatory milestone: Opna Bio’s zavabresib (OPN-2853), a selective BET inhibitor, received FDA orphan drug designation for myelofibrosis. An investigator-sponsored trial combining zavabresib with ruxolitinib showed durable spleen reduction in advanced myelofibrosis patients with inadequate ruxolitinib response.
Why this matters
Splenomegaly remains a dominant driver of symptom burden in myelofibrosis, and patients with inadequate response to ruxolitinib monotherapy have limited options for further spleen reduction without dose-limiting cytopenias. Zavabresib’s orphan designation and reported durable spleen response in this population expand the growing portfolio of ruxolitinib add-on strategies (alongside navitoclax, selinexor, elritercept) targeting refractory splenomegaly through distinct mechanisms — here, epigenetic modulation via selective BET inhibition.