Nurix Therapeutics announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to NX-5948, an investigational, orally bioavailable, small molecule degrader of Bruton’s tyrosine kinase (BTK), for the treatment of adult patients with relapsed or refractory chronic lymphocytic leukemia or small lymphocytic lymphoma (r/r CLL/SLL) after at least two lines of therapy, including a BTK inhibitor (BTKi) and a B-cell lymphoma 2 (BCL2) inhibitor. The Fast Track designation is intended to facilitate the development and expedite the review of drugs to treat serious conditions and fill an unmet medical need.
Clinical Significance
The Fast Track designation highlights the potential of NX-5948 to address a critical unmet need in CLL/SLL patients who have exhausted existing treatment options. According to Arthur T. Sands, M.D., Ph.D., president and chief executive officer of Nurix, this recognition underscores the importance of developing new therapies for patients whose cancer has progressed following BTK and BCL2 inhibitor therapy. The designation is supported by encouraging safety and efficacy data from an ongoing Phase 1 clinical trial, suggesting the potential for durable clinical benefits.
Phase 1 Clinical Trial Data
Nurix recently presented positive clinical data from the dose escalation stage of its Phase 1a/1b clinical trial evaluating daily oral dosing of NX-5948 in patients with r/r B-cell malignancies at the American Society of Hematology (ASH) meeting in December 2023. The data showed that six of seven CLL patients receiving doses from 50 to 200 mg demonstrated clinical benefit, with three achieving partial responses (PRs) that were ongoing as of the October 17, 2023, data cut. NX-5948 was well-tolerated across all tested doses, with no dose-limiting toxicities (DLTs) or treatment-related serious adverse events (SAEs) and no treatment-emergent adverse events (TEAEs) leading to drug discontinuation. Notably, there were no incidences of atrial fibrillation or hypertension.
About NX-5948
NX-5948 is being evaluated in a Phase 1 clinical trial (NCT05131022) in patients with relapsed or refractory B-cell malignancies. Preclinical data suggest that NX-5948 is highly potent against tumor cell lines resistant to current BTK inhibitors, making it a promising candidate for heavily pretreated CLL/SLL patient populations. Dose escalation is ongoing across all indications, and the study is actively enrolling patients in the United States, the United Kingdom, and the Netherlands. Additional data with higher dose levels and longer treatment duration are expected in 2024.
Implications of Fast Track Designation
The FDA's Fast Track designation provides several potential benefits, including more frequent interactions with the FDA to discuss the drug's development plan and eligibility for Accelerated Approval and Priority Review if relevant criteria are met. This designation can significantly expedite the development and potential approval of NX-5948, offering a potential new treatment option for patients with relapsed or refractory CLL/SLL more quickly.
