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

Inhibrx Biosciences has announced promising phase 2 results for its antibody ozekibart in the treatment of chondrosarcoma, a rare bone cancer with no currently approved treatments. The San Diego-based biotech is now planning to submit the drug for FDA approval in the second quarter of 2026.

Ozekibart's Phase 2 Success

The ChonDRAgon trial, which enrolled 206 patients with advanced or metastatic chondrosarcoma, demonstrated that ozekibart reduced the risk of disease progression or death by 52% compared to placebo. The treatment more than doubled the median progression-free survival from 2.66 months in the placebo arm to 5.52 months.

Ozekibart, designed to bind to death receptor 5 on cancer cells and trigger cell death, was administered intravenously every three weeks. The treatment was generally well-tolerated, with fatigue, constipation, and nausea being the most common side effects.

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."

Expanded Applications and Safety Considerations

Inhibrx also reported positive results from expanded phase 1 cohorts for other indications:

• Ewing sarcoma: A 64% overall response rate was observed in 25 patients when ozekibart was combined with irinotecan and temozolomide.
• Colorectal cancer: A 23% overall response rate was seen when ozekibart was used in combination with the FOLFIRI chemotherapy regimen.

However, safety concerns were noted during the trials. One patient died from liver toxicity early in the ChonDRAgon study, prompting Inhibrx to exclude patients with severe liver problems and implement stricter monitoring protocols. The treatment arm showed an 11.8% liver adverse event rate compared to 4.5% in the placebo arm, with most events being grade 1 or 2.

Inhibrx's Pipeline and Corporate Developments

Ozekibart is one of two remaining cancer assets for Inhibrx following a $1.7 billion buyout by Sanofi in January 2024. The French pharmaceutical giant acquired Inhibrx primarily for its rare disease drug INBRX-101, a candidate for alpha-1 antitrypsin deficiency, while spinning off the cancer programs into a new iteration of Inhibrx.

The company's other ongoing project is INBRX-106, a hexavalent OX40 agonist currently in phase 2/3 trials for head and neck squamous cell carcinoma and phase 1/2 trials for solid tumors, both in combination with Merck's Keytruda.

Mark Lappe, Inhibrx's co-founder and CEO, expressed optimism about the future, stating, "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. We look forward to working with the FDA to deliver ozekibart to patients as swiftly as possible."