Inhibrx's Ozekibart Shows Promise in Rare Bone Cancers, Eyes FDA Submission

Inhibrx Biosciences has announced promising results for its antibody therapy ozekibart in treating rare bone cancers, setting the stage for a potential FDA submission in 2026. The San Diego-based biotech reported significant progress in both chondrosarcoma and Ewing sarcoma trials, marking a potential breakthrough in areas with limited treatment options.

Chondrosarcoma Phase 2 Success

Ozekibart demonstrated impressive efficacy in a phase 2 trial for advanced or metastatic chondrosarcoma, a rare bone cancer affecting approximately one in 200,000 people in the U.S. The ChonDRAgon trial, involving 206 patients, showed that ozekibart reduced the risk of disease progression or death by 52% compared to placebo. Notably, the median progression-free survival more than doubled from 2.66 months in the placebo arm to 5.52 months with ozekibart treatment.

Dr. Robin Jones, head of the sarcoma unit at The Royal Marsden Hospital in London, expressed enthusiasm about the results, stating, "With no approved treatments available, we have observed that ozekibart helps to keep the cancer from growing, improves how patients feel and restores a sense of hope."

The treatment, administered via intravenous infusion every three weeks, was generally well-tolerated. Common side effects included fatigue, constipation, and nausea. However, the study did reveal a higher incidence of liver-related adverse events in the treatment arm (11.8%) compared to the placebo arm (4.5%), prompting stricter monitoring protocols.

Promising Results in Ewing Sarcoma and Colorectal Cancer

In addition to the chondrosarcoma data, Inhibrx reported encouraging results from expanded phase 1 cohorts. In Ewing sarcoma, another rare bone cancer, ozekibart achieved a 64% overall response rate in 25 patients when combined with irinotecan and temozolomide. The drug also showed promise in colorectal cancer, with a 23% overall response rate in combination with the FOLFIRI chemotherapy regimen.

Mark Lappe, Inhibrx's co-founder and CEO, commented on the broader potential of ozekibart, saying, "We are excited by these results which suggest the potential of ozekibart to expand not only in sarcomas but also in high unmet need solid tumor indications."

Path Forward and Company Background

Based on these positive outcomes, Inhibrx plans to submit ozekibart for FDA approval in the second quarter of 2026. This development comes in the wake of significant corporate changes for Inhibrx. In January 2024, Sanofi acquired Inhibrx in a $1.7 billion deal primarily aimed at obtaining INBRX-101, a rare disease drug candidate for alpha-1 antitrypsin deficiency. As part of this transaction, Sanofi spun out Inhibrx's cancer assets, including ozekibart, into a new entity.

Inhibrx's current pipeline also includes INBRX-106, a hexavalent OX40 agonist being tested in combination with Merck's Keytruda in phase 2/3 trials for head and neck squamous cell carcinoma and a phase 1/2 solid tumor trial. The company recently discontinued development of INBRX-105, an anti-PD-L1 x 4-1BB bispecific, due to unsatisfactory results in early-stage trials.