On March 17, 2025 Nurix Therapeutics, Inc. (Nasdaq: NRIX), a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of targeted protein degradation medicines, reported that the U.S. Food and Drug Administration (FDA) has granted Orphan Drug Designation (ODD) to bexobrutideg (NX-5948) for the treatment of Waldenström macroglobulinemia (WM) (Press release, Nurix Therapeutics, MAR 17, 2025, View Source [SID1234651184]). Bexobrutideg is an orally bioavailable, brain penetrant degrader of BTK which is being evaluated in an ongoing Phase 1a/b clinical trial in adults with relapsed or refractory B-cell malignancies.
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The FDA’s Orphan Drug Designation program provides orphan status to therapies intended for the treatment, diagnosis, or prevention of rare diseases that affect fewer than 200,000 people in the United States. This designation provides certain benefits, including tax credits for qualified clinical testing, waiver or partial payment of FDA application fees and seven years of market exclusivity, if approved.
"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, M.D., Ph.D., president and chief executive officer of Nurix. "Granting of the designation highlights bexobrutideg’s potential to provide patients with WM a promising new therapeutic option. We are also pleased to announce that our investigational therapy bexobrutideg has been assigned a nonproprietary name reflecting its novel mechanism of action, designated with the unique suffix "deg" for degrader."
In collaboration with the national naming authority, United States Adopted Name (USAN) Council, Nurix’s lead BTK degrader, NX-5948, was assigned the nonproprietary name "bexobrutideg." The U.S. and international drug naming convention is designed to select a single name of worldwide acceptability for each active substance that is intended to be marketed as a pharmaceutical. Most notable with bexobrutideg is the designation of a new suffix, "deg," which references bexobrutideg’s novel degradation mode of action. Targeted protein degraders are characterized by their bifunctional nature, binding to both a target protein and a ligase to drive ubiquitination and catalytic degradation of the target through the proteasome. The new deg suffix is an important recognition that the mechanism of action, pharmacokinetics and pharmacodynamics of targeted protein degraders are fundamentally different than inhibitors, which all use the "ib" suffix. The central stem of the name, "bruti," references the target, Bruton’s tyrosine kinase (as used in ibrutinib, zanubrutinib and acalabrutinib). The prefix "bexo" is the unique identifier of a specific agent in the class and is often used for ease of reference to the agent.
"We are excited that bexobrutideg has been recognized by the USAN Council as a unique entity and member of a new class of small molecule drugs, targeted protein degraders," said Gwenn Hansen, Ph.D., chief scientific officer of Nurix. "The catalytic mechanism of action and event driven pharmacology triggering ubiquitination and proteasomal degradation of a target protein is highly differentiated from inhibitors and allows degraders to eliminate the totality of a protein’s function. In our BTK degrader clinical program, we have also established that degraders can eliminate mutant oncoproteins that have proven to be resistant to inhibitor therapy."
About Bexobrutideg (NX-5948)
Bexobrutideg is an investigational, orally bioavailable, brain penetrant, small molecule degrader of BTK that is currently being evaluated in a Phase 1 clinical trial in patients with relapsed or refractory B cell malignancies. Nurix has previously reported encouraging safety and efficacy data in patients with WM treated in the ongoing Phase 1a/b clinical trial of bexobrutideg demonstrating early promise of clinical benefit with potential for durable outcomes. Nurix continues to enroll patients with WM in an ongoing Phase 1b expansion cohort and anticipates sharing additional clinical data in 2025. Additional information on the ongoing clinical trial can be accessed at clinicaltrials.gov (NCT05131022). Nurix is also developing bexobrutideg for the potential treatment of inflammatory diseases.
About Waldenström Macroglobulinemia (WM)
WM is a rare, slow growing type of non-Hodgkin’s lymphoma that is characterized by the replacement of normal bone marrow cells by malignant lymphocytic cells that produce monoclonal IgM. This replacement leads to anemia, bleeding, and impaired immune function, while the elevated IgM levels may cause neurologic symptoms. The incidence of Waldenström macroglobulinemia ranges from 0.361,2 to 0.573 per 100,000 people in the United States or approximately 1,200 to 1,900 annually. With a median disease duration approaching 10 years, 4 approximately 12,000 to 19,000 patients are living with Waldenstrom’s macroglobulinemia in the United States. Recommended first-line treatments including chemoimmunotherapy and BTK inhibitor (BTKi) therapy. There are no therapies approved to treat WM patients after a BTKi.