UBX-303-1

UBX-303-1 (UBX-303061, BTK Degrader UBX-303061) is an oral targeted protein degrader (chimeric degrader; company term 'Degraducer') from Ubix Therapeutics. Breaks down Bruton's tyrosine kinase rather than only blocking it: one end binds BTK and the other an E3 ubiquitin ligase, which tags BTK for destruction. The company reports activity in preclinical models with normal BTK and with the C481S resistance mutation. Its furthest stage is phase 1, for relapsed or refractory B-cell malignancies (CLL/SLL, DLBCL, follicular, mantle cell, marginal zone lymphoma, Waldenström macroglobulinaemia). ClinicalTrials.gov registers it in one study linked below. Phase 1a/1b NCT06590961 recruiting; started 20 February 2025. Whether it works in people has not been established unless a trial below reports it.