Inhibrx's DR5 antibody ozekibart heads to FDA review after halving progression risk
The ChonDRAgon trial met its primary endpoint with a 52% reduction in progression or death versus placebo, setting up an April 2027 FDA decision in a cancer with no approved systemic therapy.
Executive Summary
- The FDA has accepted Inhibrx's marketing application for ozekibart in a rare bone cancer and set a decision date, moving the program from a completed randomized trial into formal review.
- The decision rests on a randomized, placebo-controlled trial that already showed a clear reduction in the risk of tumor progression or death, in a disease where no systemic treatment has ever been approved.
- No other therapy targeting the same death-receptor pathway is active in this cancer, and the broader indication has almost no late-stage drug development, leaving the FDA's read of this single trial as the field's only near-term test.
- Review will turn on whether the agency treats the disclosed efficacy data as sufficient on its own, since designation history and label scope have not yet been established.
The filing
Inhibrx Biosciences, Inc. said on June 15, 2026 that the FDA accepted its BLA for ozekibart (INBRX-109) in patients with unresectable or metastatic conventional chondrosarcoma and identified no filing review issues, setting a PDUFA goal date of April 14, 2027. The application is a biologics license application (a marketing application for a biologic drug) tied to NCT04950075, the ChonDRAgon study. Chondrosarcoma is the second most common primary bone malignancy, and once it becomes unresectable or metastatic, surgical resection is the only established management option, leaving no approved systemic treatment on the market. Inhibrx+1Inhibrx Announces U.S. FDA Acceptance of BLA for Ozekibart in Patients with Conventional ChondrosarcomaJun 15, 2026Study of INBRX-109 in Conventional ChondrosarcomaNCT04950075
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
The trial result
ChonDRAgon, a 206-patient randomized, blinded, placebo-controlled Phase 2 trial across 67 sites in the United States and eight other countries, tested ozekibart against placebo on progression-free survival by independent radiology review. The trial met its primary endpoint: ozekibart reduced the risk of progression or death by 52% versus placebo, with a stratified hazard ratio of 0.479 (95% CI: 0.33-0.68; P<0.0001), and median progression-free survival more than doubled to 5.52 months versus 2.66 months for placebo. Inhibrx Chief Executive Officer Mark Lappe called the filing acceptance "a monumental milestone for Inhibrx and, more importantly, for the chondrosarcoma community". Ozekibart is a tetravalent antibody that agonizes death receptor 5 (DR5), a mechanism designed to trigger tumor cell death, and it holds Fast Track and orphan drug designations for this indication, granted by the FDA in January and November 2021, respectively. NCT04950075+1Study of INBRX-109 in Conventional ChondrosarcomaNCT04950075Inhibrx Announces U.S. FDA Acceptance of BLA for Ozekibart in Patients with Conventional ChondrosarcomaJun 15, 2026
The competitive field
No other trial targeting DR5 is active in conventional chondrosarcoma, and the only other drug in Phase 3 development for this indication, Servier's ivosidenib, works through a different mechanism (IDH1 inhibition) rather than DR5 agonism. Earlier DR5-agonist programs from other sponsors, including Genentech's apomab and dulanermin, Daiichi Sankyo's tigatuzumab, and AbbVie's eftozanermin alfa, tested the same target class in other solid tumors and lymphomas but not in chondrosarcoma, and none reached a positive randomized readout in this disease. Ozekibart's own earlier-phase study in broader solid tumors and sarcomas, NCT03715933, remains active. The mechanism has no validated regulatory precedent in this specific indication, which is what makes the ChonDRAgon result the field's first randomized positive signal for DR5 agonism in a bone sarcoma.
The trial's operational path
The registry shows the trial's primary completion date moved three times since 2021, from February 2024 to December 2024, then to September 2025, alongside a status change to Active, not recruiting and an enrollment update from 201 to 206 patients recorded in January 2026. That enrollment change sits within the routine band the operational model uses to flag concern, and the trial ultimately completed with the primary analysis already read out and disclosed publicly before the BLA submission. NCT04950075Study of INBRX-109 in Conventional ChondrosarcomaNCT04950075
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.