8-K: Inhibrx Ozekibart Shines in Chondrosarcoma Trial

Inhibrx Biosciences announced positive topline results from its registrational trial of ozekibart in chondrosarcoma, along with encouraging updates for colorectal cancer and Ewing sarcoma cohorts.

Summary

• Ozekibart (INBRX-109) met its primary endpoint in the registrational ChonDRAgon study for advanced or metastatic, unresectable chondrosarcoma.
• The study demonstrated a 52% reduction in the risk of disease progression or death compared to placebo (stratified Hazard Ratio [HR] 0.479; 95% CI: 0.33, 0.68; P<0.0001).
• Median progression-free survival (PFS) more than doubled to 5.52 months for ozekibart compared to 2.66 months for placebo.
• Ozekibart is the first investigational therapy to show a significant PFS benefit in a randomized trial for chondrosarcoma, a disease with no approved systemic options.
• Key secondary endpoints, including disease control rate (54% vs 27.5% for placebo) and delay to deterioration in pain and physical function, further supported the clinical benefit.
• Ozekibart was generally well tolerated, with common treatment-related adverse events including fatigue, constipation, and nausea.
• One hepatotoxicity-related fatal event occurred early in the study, prior to the implementation of mitigation measures; subsequent measures effectively managed this risk, resulting in a low overall incidence of treatment-related hepatic adverse events (11.8% vs 4.5% in placebo arm).
• In the colorectal cancer (CRC) expansion cohort (44 patients enrolled, 26 evaluable), ozekibart in combination with FOLFIRI showed a 23% overall response rate (ORR) and a 92% disease control rate (DCR) in heavily pretreated patients.
• In the Ewing sarcoma expansion cohort (33 patients recruited, 25 evaluable), ozekibart in combination with irinotecan and temozolomide (IRI/TMZ) demonstrated a 64% ORR and a 92% DCR in a difficult-to-treat patient population.
• Plans are in place to submit a Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) for ozekibart in chondrosarcoma in the second quarter of 2026.

Sentiment

Score: 9

Explanation: The filing reports highly positive topline results from a registrational trial for a rare cancer with no approved treatments, along with very encouraging interim data for two other difficult-to-treat cancers. This represents significant clinical progress and potential for regulatory approval, despite a past fatal adverse event that has since been mitigated.

Positives

• Ozekibart achieved a statistically significant and clinically meaningful median progression-free survival (PFS) in chondrosarcoma, more than doubling it to 5.52 months compared to 2.66 months for placebo (P<0.0001).
• Ozekibart is the first investigational therapy to demonstrate a significant PFS benefit in a randomized trial for chondrosarcoma, a disease with no approved systemic options.
• The benefit of ozekibart in chondrosarcoma was consistent across all pre-specified subgroups, including IDH-wild-type and IDH-mutant tumors.
• Key secondary endpoints in chondrosarcoma, including a disease control rate of 54% (vs 27.5% for placebo) and a delay to deterioration in pain and physical function, further supported the clinical benefit.
• Highly encouraging 23% overall response rate (ORR) and 92% disease control rate (DCR) observed in heavily pretreated colorectal cancer patients, significantly exceeding typical response rates of 5-6% with current standard of care.
• Highly encouraging 64% ORR and 92% DCR observed in refractory Ewing sarcoma patients, substantially higher than the 15-30% ORR typically seen with standard IRI/TMZ.
• Ozekibart was generally well tolerated across all indications, with manageable safety profiles consistent with known adverse events of combination therapies.
• Effective mitigation measures were implemented in the chondrosarcoma trial to manage hepatotoxicity risk, leading to a low overall incidence of treatment-related hepatic adverse events (11.8% vs 4.5% placebo), mostly Grade 1 or 2.

Negatives

• One hepatotoxicity-related fatal event occurred early in the chondrosarcoma study, prior to the implementation of mitigation measures.
• The overall incidence of treatment-related hepatic adverse events in the chondrosarcoma trial was 11.8% in the ozekibart arm compared to 4.5% in the placebo arm.
• Common treatment-related adverse events for ozekibart in chondrosarcoma included fatigue, constipation, and nausea.
• Common treatment-emergent adverse events for ozekibart in combination with FOLFIRI in colorectal cancer included anemia, diarrhea, nausea, and fatigue.
• Common adverse events for ozekibart in combination with IRI/TMZ in Ewing sarcoma included diarrhea, nausea, anemia, and fatigue.

Risks

• Topline data may not accurately reflect the complete results of a particular study or trial and remain subject to audit, and final data may differ materially from topline data.
• Uncertainties regarding the initiation, timing, progress, and results of preclinical studies and clinical trials, and research and development programs.
• Ability to advance therapeutic candidates into, and successfully complete, clinical trials.
• Interpretation of topline, interim, or preliminary data from clinical trials, including interpretations regarding disease control and disease response.
• Results from preclinical studies or early clinical trials not necessarily being predictive of future results.
• Unexpected adverse side effects or inadequate efficacy of therapeutic candidates that may limit their development, regulatory approval, and/or commercialization.
• Potential for programs and prospects to be negatively impacted by developments relating to competitors, including results of studies or regulatory determinations.
• Timing or likelihood of regulatory filings and approvals and regulatory developments in the U.S. and foreign countries.
• Successful commercialization of therapeutic candidates, if approved.
• An accelerated development or approval pathway may not be available for ozekibart or other therapeutic candidates, and any such pathway may not lead to a faster development process.
• May not realize the benefits associated with orphan drug designation, including that orphan drug exclusivity may not effectively protect a product from competition and that such exclusivity may not be maintained.
• Pricing, coverage, and reimbursement of therapeutic candidates, if approved.
• Ability to utilize the technology platform to generate and advance additional therapeutic candidates.

Future Outlook

Plans to submit a Biologics License Application (BLA) for ozekibart in chondrosarcoma to the U.S. Food and Drug Administration in the second quarter of 2026. The company is also exploring ozekibart's potential in other high unmet need solid tumor indications, including colorectal cancer and Ewing sarcoma, based on encouraging early signals from ongoing expansion cohorts.

Management Comments

• Dr. Robin Jones, head of the sarcoma unit at The Royal Marsden Hospital in London, United Kingdom: "I am very encouraged and enthusiastic about ozekibart and the impact I have seen on my sarcoma patients. 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 for my patients."
• Mark Lappe, CEO and Co-Founder of Inhibrx: "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."

Industry Context

The announcement positions ozekibart as a potential breakthrough in chondrosarcoma, a rare disease with no approved systemic treatment options, addressing a significant unmet medical need. The encouraging interim data in heavily pretreated colorectal cancer and refractory Ewing sarcoma also suggests ozekibart could offer new therapeutic avenues in patient populations with poor outcomes and limited standard-of-care efficacy, potentially expanding its market beyond rare sarcomas into broader oncology indications. This could establish Inhibrx as a key player in developing novel biologic therapeutics for difficult-to-treat cancers.

Comparison to Industry Standards

• Chondrosarcoma: Ozekibart is the first investigational therapy to demonstrate a statistically significant progression-free survival benefit in a randomized trial for this disease, which currently has no approved systemic options.
• Colorectal Cancer: The 23% overall response rate (ORR) observed with ozekibart in combination with FOLFIRI in heavily pretreated patients is highly encouraging compared to the typical 5-6% ORR seen with current standard of care.
• Ewing Sarcoma: The 64% ORR with ozekibart in combination with IRI/TMZ is substantially higher than the 15-30% ORR typically observed with standard IRI/TMZ in this difficult-to-treat patient population.

Stakeholder Impact

• Shareholders: Positive clinical trial results and a clear path to BLA submission for chondrosarcoma, along with promising data in other indications, are highly likely to increase investor confidence and potentially share value.
• Patients: Ozekibart offers a significant new treatment option for chondrosarcoma, a disease with no approved systemic therapies, and shows encouraging potential for patients with heavily pretreated colorectal cancer and refractory Ewing sarcoma, addressing high unmet medical needs.
• Healthcare Providers: The data provides evidence for a new therapeutic approach for difficult-to-treat cancers, potentially expanding their treatment arsenal.
• Regulatory Authorities: The positive registrational trial results will be a key input for the FDA's review process for the planned BLA submission.

Next Steps

• Detailed results from the chondrosarcoma trial will be presented at the Connective Tissue Oncology Society (CTOS) Annual Meeting on November 14, 2025.
• Submit a Biologics License Application (BLA) to the U.S. Food and Drug Administration in the second quarter of 2026 for ozekibart in chondrosarcoma.
• Continue ongoing expansion cohorts investigating ozekibart in combination with FOLFIRI in late-line colorectal cancer and in combination with irinotecan and temozolomide in refractory Ewing sarcoma.
• Host a conference call on October 23, 2025, to further discuss the results and ongoing cohorts.
• Update the corporate presentation on the company's website.

Key Dates

Recommendation

The positive topline results from the registrational ChonDRAgon study for ozekibart in chondrosarcoma, demonstrating a statistically significant and clinically meaningful doubling of median progression-free survival in a disease with no approved systemic options, represent a major de-risking event and a significant market opportunity. Coupled with highly encouraging interim data from expansion cohorts in heavily pretreated colorectal cancer and refractory Ewing sarcoma, which show superior response rates compared to current standards of care, the company's pipeline demonstrates strong potential. The planned BLA submission in Q2 2026 provides a clear near-term catalyst. While there was a past fatal adverse event, it was mitigated, and the overall safety profile is manageable. These results suggest a strong growth trajectory and significant value creation potential for investors.

Keywords

Inhibrx Biosciences, INBX, Ozekibart, INBRX-109, Chondrosarcoma, Colorectal Cancer, Ewing Sarcoma, Oncology, Rare Diseases, Clinical Trial, Registrational Study, Progression-Free Survival, Overall Response Rate, Disease Control Rate, FDA BLA, Biologics License Application, DR5 Agonist, Biopharmaceutical, Clinical-stage, Sarcoma, Solid Tumor