Nurix and Roche enrol first patient in Phase 3 bexobrutideg CLL trial
Nurix Therapeutics has announced the enrolment of the first patient in its registrational Phase 3 DAYBreak CLL-306 trial, evaluating bexobrutideg against pirtobrutinib in patients with relapsed or refractory chronic lymphocytic leukaemia and small lymphocytic lymphoma who have previously received a covalent BTK inhibitor. The study is being conducted under Nurix's co-development collaboration with Roche.
The trial, listed under NCT07516093, is designed to enrol approximately 620 patients randomised 1:1 to receive either bexobrutideg 600 mg orally once daily or pirtobrutinib. It carries dual primary endpoints of objective response rate and progression-free survival, both assessed by an independent review committee. Nurix says the design is intended to support global regulatory submissions if the data are positive.
The science behind the comparison
Bexobrutideg is described by Nurix as an orally bioavailable, brain-penetrant, highly selective small-molecule degrader of Bruton's tyrosine kinase. The core hypothesis driving DAYBreak CLL-306 is that eliminating BTK protein entirely through targeted degradation will produce meaningfully different outcomes than the non-covalent inhibition mechanism used by pirtobrutinib, which blocks the protein's function without destroying it.
Arthur Sands, president and chief executive of Nurix, said the head-to-head design was intended "to test whether that differentiation translates into superior outcomes for patients," adding that the company and Roche aim to realise the potential of BTK degradation across oncology, immunology, and neurology.
Chief medical officer Paula O'Connor noted that bexobrutideg had already shown "robust clinical activity" with a favourable tolerability profile in relapsed/refractory CLL in earlier studies, though detailed data from the pivotal single-arm Phase 2 DAYBreak CLL-201 study have not yet been presented.
Market and competitive context
The relapsed/refractory CLL market has undergone substantial change over the past decade. Covalent BTK inhibitors ibrutinib and acalabrutinib became standard of care but are limited by resistance mutations that emerge at the BTK binding site. Pirtobrutinib, a non-covalent inhibitor approved by the FDA in 2023, was specifically designed to overcome those resistance patterns, and its selection as the comparator arm is a deliberate statement of intent: Nurix is not merely benchmarking against an older generation of therapy but against the current standard of care in the post-covalent-BTK setting.
The targeted protein degradation space is attracting increasing pharmaceutical interest. Several companies, including some academic spin-outs, are pursuing PROTAC and molecular-glue degrader platforms across oncology and beyond. Nurix's partnership network is notably broad, with Roche co-developing bexobrutideg in oncology and immunology, Gilead collaborating on an IRAK4 degrader and other assets, and Sanofi engaged on a STAT6 degrader programme. That partnership density gives the company both financial resilience and a commercial read-across from partners' commercial infrastructure.
The brain-penetrant property of bexobrutideg may also prove relevant beyond CLL. Nurix is evaluating the drug in neurological indications, and a new tablet formulation is being studied in healthy volunteers to support that expansion. A head-to-head Phase 3 win in CLL would substantially strengthen the overall platform narrative.
Near-term milestones to watch include interim data from the Phase 2 DAYBreak CLL-201 study, the pace of CLL-306 enrolment across global sites, and any update on combination studies pairing bexobrutideg with venetoclax, which are planned under the NX-5948-203 protocol.