8-K: Nurix Initiates Pivotal DAYBreak Trial for Bexobrutideg

Nurix Therapeutics announced the initiation of its pivotal Phase 2 DAYBreak clinical trial for bexobrutideg in relapsed or refractory chronic lymphocytic leukemia, alongside positive updates for NX-1607 and other pipeline programs.

Summary

• Initiated the DAYBreak clinical trial, a pivotal single-arm Phase 2 study of bexobrutideg (NX-5948) for patients with relapsed or refractory chronic lymphocytic leukemia or small lymphocytic lymphoma (r/r CLL/SLL).
• The DAYBreak study will enroll approximately 100 patients with r/r CLL/SLL who have experienced disease progression following treatment with a covalent BTK inhibitor (cBTKi), a non-covalent BTK inhibitor (ncBTKi), and a BCL-2 inhibitor (BCL-2i).
• The 600 mg once daily (QD) dose of bexobrutideg has been selected for the DAYBreak study and the planned Phase 3 confirmatory study, following alignment with global regulators including the U.S. Food and Drug Administration, the U.K. Medicines and Healthcare products Regulatory Agency, and the European Medicines Agency.
• A randomized confirmatory Phase 3 trial for bexobrutideg in r/r CLL/SLL patients (whose disease progressed while receiving a cBTKi) is planned for initiation in the first half of 2026, enrolling approximately 400 patients.
• A Phase 1b/2 combination study of bexobrutideg in CLL/SLL, with an initial focus on combinations with current standards of care including BCL-2 inhibitors and anti-CD20 antibodies, is also planned for initiation in the first half of 2026.
• New clinical data from the Phase 1a study of NX-1607, a first-in-class oral CBL-B inhibitor, in 82 patients with relapsed/refractory solid tumors showed dose-dependent exposure, evidence of peripheral immune activation, and clinical activity, including a confirmed partial response in a patient with micro-satellite stable colorectal cancer (MSS CRC) and 50% PSA reductions in 6 out of 13 prostate cancer patients.
• NX-1607 demonstrated a disease control rate of 49.3% as of July 26, 2025, with 7 patients achieving stable disease or partial response for 5 months on treatment and one MSS CRC patient for 27 months.
• Nurix's pro forma cash is anticipated to be $678.8 million, providing an expected runway into 2028, upon completion of its registered direct offering.

Sentiment

Score: 8

Explanation: The filing presents significant positive clinical and regulatory milestones for bexobrutideg, including the initiation of a pivotal trial and global dose alignment, supported by strong preclinical data. Positive early clinical signals for NX-1607 and a robust financial position further contribute to a highly positive outlook, despite inherent drug development risks.

Positives

• Initiation of the pivotal Phase 2 DAYBreak trial for bexobrutideg marks a significant advancement towards potential Accelerated Approval in a high unmet need patient population (r/r CLL/SLL, triple-exposed).
• Global regulatory alignment (FDA, MHRA, EMA) on the 600 mg once daily dose for pivotal monotherapy trials provides clear guidance and reduces regulatory uncertainty.
• Bexobrutideg has consistently demonstrated strong clinical activity with an objective response rate (ORR) of 80.9% (95% CI: 66.7-90.9) in 47 CLL response-evaluable patients.
• Bexobrutideg shows durable responses, with a median duration of response not reached (NR) and 18 patients having duration of treatment exceeding 12 months.
• The safety profile of bexobrutideg is well-tolerated, with no dose-limiting toxicities, no new atrial fibrillation or ventricular arrhythmias, and no systemic fungal infections observed.
• Preclinical data support bexobrutideg as a potential best-in-class BTK degrader, demonstrating superior degradation potency (20x more potent than BGB-16673, 5x more potent than AbbVie cmpd. 1), broad coverage of clinically relevant BTK mutations, and exquisite selectivity over off-target proteins like TEC, LCK, CSK, and ADK.
• NX-1607, a first-in-class CBL-B inhibitor, demonstrated evidence of clinical activity in heavily pre-treated relapsed/refractory solid tumors, including a confirmed partial response in micro-satellite stable colorectal cancer (MSS CRC) and significant PSA reductions in prostate cancer.
• NX-1607 showed a disease control rate of 49.3% and a tolerable safety profile comparable to approved immuno-oncology agents.
• The company's pro forma cash position of $678.8 million provides an expected financial runway into 2028.
• Advancement of partnered programs (NX-0479/GS-6791 with Gilead, NX-3911 with Sanofi) towards significant regulatory and clinical milestones, with potential for substantial value creation through profit-sharing options.

Risks

• Whether the company will be able to advance, obtain regulatory approval of, and ultimately commercialize bexobrutideg.
• The timing and results of clinical trials.
• The company's ability to fund development activities and achieve development goals.
• Risks and uncertainties related to the company's ability to advance its drug candidates, obtain regulatory approval of, and ultimately commercialize its drug candidates.
• Risks and uncertainties relating to collaboration partners, including the speed of development of partnered programs and the timing and receipt of payments from collaboration partners.
• The impact of macroeconomic events and conditions, including increasing financial market volatility and uncertainty, inflation, interest rate fluctuations, instability in the global banking system, uncertainty with respect to the federal budget and debt ceiling, the impact of war, military or regional conflicts, and global health pandemics, on clinical trials and operations.
• The company's ability to protect intellectual property.
• Other risks and uncertainties described under the heading "Risk Factors" in the company's Quarterly Report on Form 10-Q for the fiscal quarter ended August 31, 2025, and other SEC filings.

Future Outlook

The company plans to initiate a randomized confirmatory Phase 3 trial for bexobrutideg in relapsed or refractory CLL/SLL patients in the first half of 2026, aiming for full regulatory approval. Additionally, a Phase 1b/2 combination study of bexobrutideg is planned for the first half of 2026 to explore expanded clinical opportunities across lines of therapy in CLL/SLL, initially focusing on combinations with BCL-2 inhibitors and anti-CD20 antibodies. Further clinical updates for bexobrutideg are expected at the American Society of Hematology (ASH) Annual Meeting in December 2025. The company anticipates its pro forma cash will provide an operational runway into 2028.

Management Comments

• "The initiation of the DAYBreak study marks Nurix's transition to a pivotal-stage company and a major milestone for bexobrutideg, which our data demonstrate has a potential best-in-class profile. With the DAYBreak study underway, we are advancing the development of bexobrutideg and are one step closer to registration and commercialization." Arthur T. Sands, M.D., Ph.D., president and chief executive officer of Nurix.
• "The favorable safety profile observed at the 600 mg bexobrutideg dose allows us to optimize its therapeutic effect, providing patients the opportunity to regain control of CLL that has progressed or has failed to respond to other therapies. With regulatory alignment, we are advancing a global registrational program intended to address a large unmet need for patients with relapsed or refractory CLL. We look forward to completing this pivotal Phase 2 study and our confirmatory Phase 3 trial as part of our comprehensive development plan designed to provide patients with a much-needed therapeutic alternative." Paula OConnor, M.D., chief medical officer of Nurix.
• "As an innovator in the field of targeted protein degradation, Nurix has generated significant data to support bexobrutideg's potential best-in-class BTK degrader profile. During our upcoming conference call, we will share highlights from our latest, unpublished preclinical data demonstrating superior degradation potency, broad coverage of clinically relevant BTK mutations, and exquisite selectivity, which together set a high bar for this class of medicines. These superior attributes strengthen our conviction that bexobrutideg may prove to be a clinically superior medicine for the treatment of patients with CLL and other B-cell driven diseases." Gwenn Hansen, Ph.D., chief scientific officer of Nurix.

Industry Context

The biopharmaceutical industry is increasingly focusing on targeted protein degradation (TPD) as a novel therapeutic modality, with Nurix positioning itself as a leader in this field. Bexobrutideg, a BTK degrader, aims to address unmet medical needs in relapsed/refractory CLL/SLL, a space where existing BTK inhibitors (covalent and non-covalent) and BCL-2 inhibitors have limitations, particularly in triple-exposed patients. The development of NX-1607, a CBL-B inhibitor, represents an innovative approach in immuno-oncology, targeting a novel immune checkpoint distinct from established PD-1/PD-L1 pathways. The company's collaborations with major pharmaceutical companies like Gilead Sciences, Sanofi S.A., and Pfizer Inc. for other degrader programs (IRAK4, STAT6) underscore the growing industry interest and validation of TPD technology for a broad range of diseases, including oncology and autoimmune conditions. The emphasis on "best-in-class" profiles for its drug candidates reflects the competitive landscape where differentiation through superior potency, mutational coverage, and selectivity is crucial for market success.

Comparison to Industry Standards

• Bexobrutideg demonstrates superior BTK degradation potency, being 20 times more potent than BGB-16673 and 5 times more potent than AbbVie cmpd. 1 in human B cells.
• Bexobrutideg shows superior mutational coverage and cell killing across key resistance mutations (e.g., C481S, C481R, V416L, T474I, L528W) compared to both covalent (ibrutinib, acalabrutinib, zanubrutinib) and non-covalent (pirtobrutinib, vecabrutinib, fenebrutinib) BTK inhibitors, as well as other BTK degraders like BGB-16673 and AbbVie cmpd. 1.
• Bexobrutideg exhibits exquisite selectivity, degrading BTK without significant off-target degradation of proteins like TEC, LCK, CSK, and ADK, which are associated with potential cardiovascular or immune-related side effects observed with some other BTK inhibitors or degraders (e.g., BGB-16673 and AbbVie cmpd. 1 showed off-target liabilities including TEC and ADK degradation). This superior selectivity (64x over TEC) is anticipated to provide a safety advantage.
• NX-1607's safety profile is comparable to approved immuno-oncology agents in early development, with most adverse events being Grade 2 or less. Its mechanism of inhibiting CBL-B offers a novel immune checkpoint approach distinct from established PD-1/PD-L1 therapies, potentially addressing patient populations unresponsive to current immune checkpoint inhibitors, such as MSS CRC.
• NX-3911 (STAT6 Degrader) aims to provide biologic-like efficacy in an oral pill format, offering complete STAT6 pathway blockade. This compares favorably to existing anti-IL4Ra and anti-IL13 monoclonal antibodies and JAK inhibitors by potentially offering a more convenient and accessible treatment for Th2-mediated inflammatory disorders.
• NX-0479/GS-6791 (IRAK4 Degrader) achieves more complete blockade of TLR/IL-1R signaling pathways and broader anti-inflammatory effects than IRAK4 inhibition alone, addressing both kinase and scaffolding functions of IRAK4.

Stakeholder Impact

• Shareholders: Potential for increased shareholder value due to significant clinical advancements, regulatory alignment, and a strong financial runway. The "best-in-class" profile claims for bexobrutideg and positive early data for NX-1607 could drive future growth.
• Patients (CLL/SLL): Bexobrutideg offers a new therapeutic alternative for patients with relapsed or refractory CLL/SLL, especially those who have progressed on multiple prior therapies, addressing a high unmet medical need.
• Patients (Solid Tumors): NX-1607 provides a novel immuno-oncology approach for patients with advanced solid tumors, particularly those unresponsive to existing immune checkpoint therapies.
• Employees: Continued progress in the pipeline and strong financial health provide stability and potential for growth opportunities.
• Regulatory Authorities: Ongoing collaboration and alignment with global regulators (FDA, MHRA, EMA) on trial design and dosing.

Next Steps

• Enroll approximately 100 patients in the DAYBreak pivotal single-arm Phase 2 study of bexobrutideg.
• Initiate a randomized confirmatory Phase 3 trial of bexobrutideg in r/r CLL/SLL patients in the first half of 2026.
• Initiate a Phase 1b/2 combination study of bexobrutideg in CLL/SLL in the first half of 2026, focusing on combinations with BCL-2 inhibitors and anti-CD20 antibodies.
• Present multiple bexobrutideg abstracts at the American Society of Hematology (ASH) Annual Meeting in December 2025.
• Continue development of NX-1607 as monotherapy or in combination for advanced solid tumors.
• Advance partnered programs, including NX-0479/GS-6791 (IRAK4 degrader) with Gilead and NX-3911 (STAT6 degrader) with Sanofi.

Key Dates

Recommendation

The initiation of a pivotal Phase 2 trial for bexobrutideg, coupled with global regulatory alignment on its 600 mg dose, significantly de-risks the program and accelerates its path to potential accelerated approval. The preclinical data strongly suggest a 'best-in-class' profile for bexobrutideg, offering superior potency, mutational coverage, and selectivity compared to competitors, which could translate into a significant market advantage. Additionally, the positive early clinical signals for NX-1607 in solid tumors and a robust financial runway into 2028 further strengthen the company's position. These combined factors indicate strong potential for future value creation and make Nurix Therapeutics an attractive investment.

Keywords

Nurix Therapeutics, Bexobrutideg, NX-5948, CLL, SLL, BTK degrader, DAYBreak trial, NX-1607, CBL-B inhibitor, Oncology, Autoimmune disease, Clinical trial, Phase 2, Phase 3, Targeted protein degradation, Biopharmaceutical, Leukemia, Lymphoma, Solid tumors, Immunotherapy, Drug development, FDA, EMA, MHRA, Project Optimus, IRAK4 degrader, STAT6 degrader