FDA Grants Orphan Drug Designation to Bexobrutideg for Waldenström Macroglobulinemia

Bexobrutideg (NX-5948) has received Orphan Drug Designation  from the FDA for the treatment of Waldenström macroglobulinemia (WM), according to a press release from Nurix Therapeutics, the developer of the drug.

Bexobrutideg, an orally bioavailable, brain-penetrant Bruton tyrosine kinase (BTK) degrader, is being evaluated in an ongoing dose-escalation (phase 1a) and cohort-expansion (phase 1b) study in adult patients with relapsed or refractory B-cell malignancies.

Efficacy and safety data of bexobrutideg in patients with previously treated WM was presented at the 12th International Workshop on Waldenström’s Macroglobulinemia on October 19, 2024. Of 9 patients for whom efficacy could be evaluated, 7 (77.8%) achieved an overall response rate, and 8 had a steady decrease in immunoglobulin M (IgM) levels beginning at 8 weeks of treatment. One patient achieved a more than 90% reduction in IgM level.

The safety profile of bexobrutideg for patients with WM was consistent with that of the overall population. The most common adverse events were purpura/contusion, neutropenia, and thrombocytopenia, and were mostly low-grade.

“The FDA’s Orphan Drug Designation for bexobrutideg, also known as NX-5948, represents an important milestone in our regulatory strategy and underscores the significant unmet medical need for improved treatments for Waldenström macroglobulinemia,” said Arthur T. Sands, MD, PhD, president and chief executive officer of Nurix, in the press release. “Granting of the designation highlights bexobrutideg’s potential to provide patients with WM a promising new therapeutic option.”

References

Nurix announces U.S. FDA Orphan Drug Designation granted to bexobrutideg (NX-5948) for the Treatment of Waldenström Macroglobulinemia. News release. Nurix Therapeutics, Inc. https://ir.nurixtx.com/news-releases/news-release-details/nurix-announces-us-fda-orphan-drug-designation-granted

ClinicalTrials.gov. A study of NX-5948 in adults with relapsed/​refractory B-cell malignancies. ClinicalTrials.gov identifier: NCT05131022. Updated March 25, 2025. Accessed April 2, 2025

O’Conner P. NX-5948: BTK degrader with activity in lymphoid malignancies. Presented at: 12th International Workshop on Waldenström’s Macroglobulinemia. October 19, 2024; Prague, Czech Republic. https://www.nurixtx.com/wp-content/uploads/2025/01/2024-10-19-IWWM-Presentation.pdf