Why Is Inhibrx Biosciences (INBX) Stock Surging in Premarket Today?

Inhibrx Biosciences, Inc. (NASDAQ:INBX) experienced a dramatic surge in its stock price following the announcement of positive topline results from its registrational trial of ozekibart (INBRX-109) in chondrosarcoma, a rare and aggressive form of bone cancer.

The stock soared over 60% in premarket trading on October 24, 2025, jumping from a previous close of $31.52 to $46.30 in pre-market hours at 7:44 AM EDT, representing a remarkable 63.26% gain. The ChonDRAgon study met its primary endpoint, demonstrating statistically significant improvement in median progression-free survival compared to placebo, marking a potential breakthrough in treating this difficult-to-treat cancer.

Strong Efficacy and Safety Results Boost Investor Optimism

The ChonDRAgon study delivered compelling efficacy data that exceeded market expectations. Ozekibart achieved a 52% reduction in the risk of disease progression or death compared to placebo, with median progression-free survival improving from 2.66 months to 5.52 months—more than doubling the previous standard. The disease control rate reached 54% versus 27.5% for placebo, with consistent benefits observed across all pre-specified subgroups. This represents the first investigational therapy to demonstrate a significant survival benefit for chondrosarcoma in a randomized study.

Key secondary endpoints further validated ozekibart’s therapeutic potential. The treatment delayed deterioration in pain and physical function, providing meaningful improvements in patient quality of life. The drug was generally well-tolerated with a manageable safety profile, though hepatotoxicity was noted as a risk requiring mitigation measures. Common treatment-related adverse events included fatigue, constipation, and nausea, which were manageable in the clinical setting.

Ozekibart works by targeting the DR5 (Death Receptor 5) pathway, which triggers cell death in tumor cells. Chondrosarcoma is one of the most difficult bone cancers to treat, with limited therapy options and poor prognosis, making this breakthrough particularly significant for patients with unresectable or metastatic conventional chondrosarcoma.

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Shares Surge Ahead of FDA Filing Planned for Q2 2026

Inhibrx Biosciences closed at $28.36 on October 23, 2025, down 10.03% from the previous session, before surging to $46.30 in pre-market trading the following morning. The company’s market capitalization stood at approximately $410.8 million, with a 52-week range of $10.81 to $39.27. Trading volume spiked dramatically to 1,151,537 shares compared to an average volume of 151,435, reflecting intense investor interest in the trial results.

The company plans to file a Biologics License Application (BLA) with the U.S. Food and Drug Administration in the second quarter of 2026. Inhibrx intends to discuss the Phase 2 data with the FDA as it prepares its regulatory submission. Detailed results from the chondrosarcoma trial will be presented at the Connective Tissue Oncology Society Annual Meeting on November 14, 2025, providing additional transparency for the medical and investment communities.

Inhibrx also reported promising interim data from expansion cohorts exploring ozekibart in colorectal cancer and Ewing sarcoma. In heavily pretreated colorectal cancer patients, the drug combined with FOLFIRI demonstrated a 23% overall response rate and 92% disease control rate. For Ewing sarcoma, ozekibart combined with irinotecan and temozolomide showed a 64% overall response rate and 92% disease control rate, suggesting broader potential applications beyond chondrosarcoma.

Disclaimer: The author does not hold or have a position in any securities discussed in the article. All stock prices were quoted at the time of writing.