Business Context and Reporting Period
Company: Inhibrx Biosciences, Inc. (INBX)
Filing Type: Form 8-K (Current Report)
Date of Report: September 8, 2026
Subject: Regulation FD Disclosure and Other Events regarding updated Phase 2 clinical data for INBRX-106 in first-line head and neck squamous cell carcinoma (HNSCC).
Key Financial Metrics
This filing is a Current Report on Form 8-K focused on clinical trial results and does not contain financial statements. Consequently, the filing text does not provide clear values for revenue, profit, cash flow, margins, debt, or liquidity.
Material Changes and Clinical Results
The Company announced primary endpoint results from the randomized Phase 2 portion of the HexAgon study evaluating INBRX-106 (a hexavalent OX40 agonist) plus pembrolizumab versus pembrolizumab monotherapy in first-line, PD-L1 positive (CPS ≥ 20) metastatic or unresectable recurrent HNSCC.
- Study Population: 68 randomized patients (63 evaluable); 29 in combination arm, 34 in control arm.
- Confirmed Objective Response Rate (cORR): 48.3% for combination arm vs. 26.5% for pembrolizumab alone.
- Complete Responses: 13.8% (4 patients) in combination arm vs. 0% in control arm.
- Median Progression-Free Survival (PFS): 9.6 months (combination) vs. 4.9 months (control).
- Six-Month PFS Rates: 72.4% (combination) vs. 42.8% (control).
- HPV+ Subgroup Results:
- cORR: 80.0% (combination) vs. 33.3% (control).
- Complete Responses: 30.0% (combination) vs. 0% (control).
- Six-Month PFS: 90.0% (combination) vs. 33.0% (control).
- Median PFS: Not reached (combination) vs. 4.6 months (control).
- Safety: Generally manageable; most common adverse events were rash, fatigue, and diarrhea (predominantly low grade).
Guidance, Outlook, and Risks
Future Plans:
- Expand the randomized Phase 2 HexAgon trial by approximately 50 additional HPV+ Oropharyngeal Squamous Cell Carcinoma (OPSCC) patients (CPS ≥ 1) to support a potential accelerated regulatory pathway.
- Align with the FDA on the framework following expansion and initiate the Phase 3 confirmatory study.
- Continue Phase 1/2 study of INBRX-106 in the perioperative setting of non-small cell lung cancer (NSCLC), with initial results targeted by mid-2027.
- Explore combinations of INBRX-106 with therapeutic cancer vaccines.
Risks and Contingencies:
- Topline data may not accurately reflect final results and remain subject to audit.
- Early clinical trial results are not necessarily predictive of future results.
- Accelerated approval pathways may not be available or may not lead to faster development.
- Standard risks regarding clinical trial initiation, progress, adverse side effects, and regulatory approvals apply.
Investor Verification Checklist
- Verify the final audited data for the HexAgon Phase 2 study to confirm the reported cORR and PFS metrics.
- Monitor the timeline and enrollment progress for the planned 50-patient expansion cohort in HPV+ OPSCC.
- Confirm the specific regulatory feedback received from the FDA regarding the accelerated approval pathway.
- Review the Company's cash runway and capital requirements to fund the Phase 3 trial and NSCLC study, as this filing does not disclose financial status.
- Track the mid-2027 data readout for the NSCLC perioperative study.