Inhibrx's INBRX-106 Nearly Doubles Response Rate and Achieves Interim Median PFS of 9.6 months in Phase 2 HNSCC Study

Phase 2 HexAgon data indicate INBRX-106 may substantially boost pembrolizumab efficacy, particularly in HPV-positive head and neck cancer.

Rhea-AI Summary

Inhibrx (INBX) reported positive primary endpoint results from the randomized Phase 2 HexAgon study of OX40 agonist INBRX-106 plus pembrolizumab in first-line PD-L1–positive metastatic or unresectable recurrent HNSCC. Among 63 evaluable patients, confirmed objective response rate was 48.3% for the combination versus 26.5% for pembrolizumab alone, with complete responses in 13.8% vs 0% of patients, respectively.

Interim median progression-free survival was 9.6 months for the combination versus 4.9 months for control, and six‑month PFS rates were 72.4% vs 42.8%. In HPV+ patients, cORR reached 80.0% with INBRX-106 plus pembrolizumab versus 33.3% for pembrolizumab alone, with a 30.0% complete response rate and 90.0% six‑month PFS; median PFS in this subgroup has not yet been reached. Treatment‑related rash, fatigue and diarrhea were mostly low grade. Inhibrx plans to add ~50 HPV+ OPSCC patients to Phase 2 to support a potential accelerated approval path and then initiate a Phase 3 confirmatory trial.

Positive

• cORR 48.3% vs 26.5% for INBRX-106 plus pembrolizumab versus pembrolizumab alone in Phase 2 HNSCC
• Median PFS 9.6 vs 4.9 months for combination versus control arm at interim analysis
• Six‑month PFS rate improved from 42.8% to 72.4% with INBRX-106 plus pembrolizumab
• In HPV+ patients, cORR 80.0% vs 33.3% and CR 30.0% vs 0% for combination versus control
• HPV+ six‑month PFS rate increased to 90.0% with combination versus 33.0% with pembrolizumab alone
• Company will expand Phase 2 by ~50 additional HPV+ OPSCC patients to support potential accelerated approval

Negative

• None.

News Explained

Beyond the HNSCC results already disclosed, Inhibrx says its INBRX-106 program is also in a Phase 1/2 perioperative non-small-cell lung cancer study, with initial results targeted by mid-2027; it also plans to explore combinations with therapeutic cancer vaccines.

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Details

Market reaction after Phase 2 clinical data: INBX +6.46%

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$121.85 $137.25 Day Range

$1.90B Market Cap

Following this news, INBX has gained 6.46%, reflecting a notable positive market reaction. Argus tracked a trough of -5.1% from its starting point during tracking. Our momentum scanner has triggered 17 alerts so far, indicating notable trading interest and price volatility. The stock is currently trading at $129.00. Trading volume is exceptionally heavy at 21.9x the average, suggesting very strong buying interest.

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Market Context

INBX was down -0.89% pre-headline, while the May 11 same-program update recorded -5.04%; both were p...

Analysis

INBX was down -0.89% pre-headline, while the May 11 same-program update recorded -5.04%; both were pre-publication context for this new efficacy report.

Key Figures

Confirmed objective response rate: 48.3% vs 26.5% Complete response rate: 13.8% vs 0% Median PFS: 9.6 vs 4.9 months +5 more

Confirmed objective response rate

48.3% vs 26.5%

INBRX-106 plus pembrolizumab vs pembrolizumab alone

Complete response rate

13.8% vs 0%

Combination arm vs control arm

Median PFS

9.6 vs 4.9 months

Combination arm vs control arm at August 19, 2026 data cutoff

Six-month PFS rate

72.4% vs 42.8%

Combination arm vs control arm

HPV+ cORR

80.0% vs 33.3%

Combination arm vs pembrolizumab alone

HPV+ complete response rate

30.0% vs 0%

Combination arm vs control arm

HPV+ six-month PFS rate

90.0% vs 33.0%

Combination arm vs control arm

Phase 2 expansion

Approximately 50 patients

Additional HPV+ OPSCC patients

Previous Clinical trial Reports

1 past event · Latest: May 11

Same Type 1 event

1. May 11

   Phase 2 clinical data

   24h Move

   -5.0%

   Same-program interim HNSCC data reported higher combination response rate than pembrolizumab monotherapy.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

OX40 agonist, cORR, progression-free survival, HNSCC

4 terms

OX40 agonist medical

"INBRX-106, a hexavalent OX40 agonist"

An OX40 agonist is a drug that activates the OX40 protein on immune cells to strengthen the body's T‑cell response, similar to pressing a gas pedal to make immune cells work harder. Investors watch these drugs because they are a form of immunotherapy being tested to treat cancers and immune diseases; positive clinical results can greatly increase a developer's value, while failures or safety concerns can reduce it.

cORR medical

"confirmed objective response rate (cORR) of 48.3%"

A 'corr' label marks a correction to a previously published announcement, indicating that some information—such as figures, dates, or wording—has been revised. Investors should pay attention because the correction may change the facts that affect a company’s value or outlook; think of it like a revised map that replaces a wrong route, helping you make decisions based on accurate, updated information.

progression-free survival medical

"Median progression-free survival (PFS) continues to mature"

Progression-free survival is the length of time during and after a treatment that a patient's disease does not get worse, measured from the start of treatment until the disease shows measurable signs of progression or the patient dies. Investors care because longer progression-free survival in clinical trials often signals that a drug is effective, improving chances of regulatory approval, market adoption, and revenue potential—think of it as a stopwatch showing how long a therapy can keep the illness at bay.

HNSCC medical

"metastatic or unresectable recurrent head and neck squamous cell carcinoma (HNSCC)"

HNSCC stands for head and neck squamous cell carcinoma, a type of cancer that starts in the flat lining cells that cover the surfaces of the mouth, throat and related structures. It matters to investors because treatments, clinical trial results, regulatory approvals or changes in diagnosis rates can directly affect the commercial prospects and valuation of companies developing therapies or diagnostics for this disease—think of it as a market signal tied to demand for specific medical products.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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First OX40 agonist to demonstrate clinical benefit in a randomized study

• INBRX-106 plus pembrolizumab delivers a 48.3% cORR and 72.4% of patients remain progression free at 6 months, compared with 26.5% and 42.8% for pembrolizumab alone
• Results are most pronounced in HPV+ patients, with cORR (80.0% vs 33.3%), CR rate (30.0% vs 0%), and PFS6 improvement (90.0% vs 33.0%) vs pembrolizumab alone
• Inhibrx will expand the Phase 2 study by approximately 50 HPV+ patients and may serve as a potential pathway to accelerated approval
• Positive results support large expansion opportunities into highly immunogenic tumors and combination with cancer vaccines

SAN DIEGO, Sept. 8, 2026 /PRNewswire/ -- Inhibrx Biosciences, Inc. (Nasdaq: INBX) ("Inhibrx" or the "Company"), a clinical-stage biopharmaceutical company focused on developing a broad pipeline of novel biologic therapeutic candidates, today announced the primary endpoint results from the randomized and controlled Phase 2 portion of the HexAgon study, which is evaluating the safety and efficacy of INBRX-106, a hexavalent OX40 agonist, in combination with pembrolizumab (the combination arm) versus pembrolizumab monotherapy (the control arm) in first-line patients with treatment-naïve, PD-L1 positive (CPS ≥ 20) metastatic or unresectable recurrent head and neck squamous cell carcinoma (HNSCC). Baseline prognostic factors were largely balanced between the two arms, and the study is being conducted at more than 80 sites in the United States, Europe and Asia. The Phase 2 portion of the HexAgon study included a total of 68 randomized patients, 63 of whom were evaluable for the primary endpoint analysis, including 29 patients in the combination arm (10 of which were HPV+) and 34 patients in the control arm (nine of which were HPV+).

The primary endpoint analysis, which had a data cutoff of August 19, 2026, demonstrated a confirmed objective response rate (cORR) of 48.3% for INBRX-106 plus pembrolizumab compared with 26.5% for pembrolizumab alone. Four patients (13.8%) in the combination arm achieved a complete response compared with no complete responses in the control arm. Median progression-free survival (PFS) continues to mature. As of the data cutoff, median PFS was 9.6 months for INBRX-106 plus pembrolizumab compared with 4.9 months for pembrolizumab alone, with six-month PFS rates of 72.4% and 42.8%, respectively.

The efficacy signal was particularly pronounced in patients with HPV+ disease, where the combination arm demonstrated an 80.0% cORR compared with 33.3% for pembrolizumab alone. Notably, 30.0% of the HPV+ patients treated in the combination arm achieved a complete response, compared with no complete responses in the control arm. The durability of the benefit was also particularly striking, with 90.0% of patients receiving INBRX-106 plus pembrolizumab remaining progression-free at six months compared with 33.0% who were receiving pembrolizumab alone. As of the data cutoff, median PFS in the combination arm in patients with HPV+ disease had not yet been reached compared with 4.6 months for pembrolizumab alone.

The combination of INBRX-106 and pembrolizumab was generally manageable. The most common treatment-related adverse events were rash, fatigue, and diarrhea, which were predominantly low grade.

"What is most exciting to us is the depth and durability of the responses we are seeing with INBRX-106, particularly in HPV+ disease," said Mark Lappe, co-founder and Chief Executive Officer of Inhibrx. "These results strengthen our conviction in OX40-mediated T-cell costimulation and give us a strong rationale to expand the program, not only into HPV+ disease, but also to explore the potential of INBRX-106 in other highly immunogenic tumors and in combination with cancer vaccines."

Based on these results, Inhibrx plans to expand the randomized Phase 2 portion of the HexAgon trial by approximately 50 additional HPV+ Oropharyngeal Squamous Cell Carcinoma (OPSCC) patients (CPS ≥ 1), to support a potential accelerated regulatory pathway. Following the Phase 2 expansion, the Company plans to align with the FDA on this framework and initiate the Phase 3 portion of the HexAgon trial, which is intended to serve as the confirmatory study. These results also position OX40 agonism as a promising treatment approach beyond recurrent/metastatic disease, with potential to extend durable, T-cell driven antitumor activity into earlier-stage HPV+ OPSCC.

Beyond HNSCC, Inhibrx is evaluating the potential of INBRX-106 in other highly immunogenic tumor types. The Company is currently conducting a 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. This readout is expected to provide important clinical insights to inform future development, demonstrating the potential for INBRX-106 to extend well beyond head and neck cancer into not only perioperative lung cancer, but broader solid tumor indications.

The Company also plans to explore the potential of INBRX-106 in combination with therapeutic cancer vaccines. The clinical activity and T-cell responses observed with INBRX-106 in HPV+ disease demonstrate its ability to amplify antigen-driven T-cell responses, providing strong scientific justification for cancer vaccine combination strategies.

The Company will host a live webcast presentation today, September 8, 2026, at 5:00 a.m. Pacific Time to further discuss the results. The webcast will also include a slide presentation of the data, which is also incorporated into the Company's investor deck accessible at https://inhibrx.com/inhibrx-biosciences-inc-investors/.

About the Conference Call

Investors may join via the web: https://app.webinar.net/4712m15mpwW or may listen to the call by dialing (1-888-880-3330). Please refer to Inhibrx Biosciences, Inc. or the conference ID 6981384 when calling in. The webcast will also include a slide presentation of the data, which is also incorporated into the Company's investor deck accessible at https://inhibrx.com/inhibrx-biosciences-inc-investors/. Following the webcast, the presentation may be accessed through a link on the "Events and Presentations" section of Inhibrx's website. The webcast will be available for 60 days following the event. Inhibrx will also update its corporate presentation within the "Investors" section of its website at www.inhibrx.com.

About INBRX-106

INBRX-106 is a hexavalent agonist targeting OX40 (CD134), a costimulatory receptor on T-cells. Utilizing Inhibrx's proprietary single-domain antibody (sdAb) platform, INBRX-106 is designed to achieve the high-order receptor clustering necessary for robust T-cell activation and survival, a feat that has eluded traditional bivalent antibody approaches.

About Inhibrx Biosciences, Inc.

Inhibrx Biosciences is a clinical-stage biopharmaceutical company focused on developing a broad pipeline of novel biologic therapeutic candidates. Inhibrx Biosciences utilizes diverse methods of protein engineering to address the specific requirements of complex target and disease biology, including its proprietary protein engineering platforms. Inhibrx Biosciences was incorporated in January 2024 as a direct, wholly-owned subsidiary of Inhibrx, Inc. Prior to the sale of Inhibrx, Inc. and the INBRX-101 program to Sanofi S.A., Inhibrx Biosciences acquired certain corporate infrastructure and other assets and liabilities through a series of internal restructuring transactions effected by Inhibrx, Inc. Inhibrx, Inc. also completed a distribution to holders of its shares of common stock of 92% of the issued and outstanding shares of Inhibrx Biosciences. Following such transactions, Inhibrx Biosciences' current clinical pipeline of therapeutic candidates includes ozekibart (INBRX-109) and INBRX-106, both of which utilize multivalent formats where the precise valency can be optimized in a target-centric way to mediate what we believe to be the most appropriate agonist function. For more information, please visit www.inhibrx.com.

Forward-Looking Statements

Inhibrx cautions you that statements contained in this press release regarding matters that are not historical facts are forward-looking statements. These statements are based on Inhibrx's current beliefs and expectations. These forward-looking statements include, but are not limited to, statements regarding: Inhibrx's judgments and beliefs regarding the strength of Inhibrx's pipeline; statements regarding the safety and efficacy of its therapeutic candidate, INBRX-106, based on topline and interim results; the potential for INBRX-106 to be used for the treatment of HNSCC or other indications; the clinical development of INBRX-106, including expected enrollment in an expansion cohort, data readouts, initiation of additional clinical trials, regulatory submissions and interactions, and the timing thereof; the potential accelerated approval; any presumption that topline, interim or preliminary data will be representative of final data or data in later clinical trials; and Inhibrx's plans to evaluate INBRX-106 across broader indications and to explore combinations with other therapies. Actual results may differ from those set forth in this press release due to the risks and uncertainties inherent in Inhibrx's business, including, without limitation, risks and uncertainties regarding: 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; the initiation, timing, progress and results of its preclinical studies and clinical trials, and its research and development programs; its ability to advance therapeutic candidates into, and successfully complete, clinical trials; its interpretation of topline, interim or preliminary data from its 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 its therapeutic candidates that may limit their development, regulatory approval and/or commercialization; the potential for its programs and prospects to be negatively impacted by developments relating to its competitors, including the results of studies or regulatory determinations relating to its competitors; the timing or likelihood of regulatory filings and approvals and regulatory developments in the U.S. and foreign countries; the successful commercialization of its therapeutic candidates, if approved; the pricing, coverage and reimbursement of its therapeutic candidates, if approved; an accelerated development or approval pathway may not be available for INBRX-106 or other therapeutic candidates and any such pathway may not lead to a faster development process; its ability to utilize its technology platform to generate and advance additional therapeutic candidates; and other risks described from time to time in the "Risk Factors" section of its filings with the U.S. Securities and Exchange Commission, including those described in its Annual Report on Form 10-K, its Quarterly Reports on Form 10-Q, and supplemented from time to time by its Current Reports on Form 8-K as filed from time to time. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and Inhibrx undertakes no obligation to update these statements to reflect events that occur or circumstances that exist after the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

Investor and Media Contact:

Kelly Deck, CFO
ir@inhibrx.com
858-795-4260

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SOURCE Inhibrx Biosciences, Inc.

FAQ

What is the design and patient population of the Phase 2 HexAgon study?

The Phase 2 portion of HexAgon is a randomized, controlled study comparing INBRX-106 plus pembrolizumab with pembrolizumab monotherapy in first-line, treatment‑naïve, PD‑L1 positive (CPS ≥ 20) metastatic or unresectable recurrent HNSCC. A total of 68 patients were randomized, with 63 evaluable for the primary endpoint: 29 in the combination arm (10 HPV+) and 34 in the control arm (nine HPV+). The trial is being conducted at over 80 sites across the United States, Europe and Asia.

How does Inhibrx plan to use these results for regulatory strategy and future development?

Based on the Phase 2 results, Inhibrx plans to expand the randomized HexAgon trial by approximately 50 additional HPV+ OPSCC patients with CPS ≥ 1 to support a potential accelerated regulatory pathway. After this expansion, the company plans to align with the FDA on this framework and then initiate the Phase 3 portion of HexAgon as the intended confirmatory study, with the aim of extending durable T‑cell–driven antitumor activity into earlier‑stage HPV+ OPSCC.

In which other indications is INBRX-106 being evaluated or planned for evaluation?

Beyond HNSCC, Inhibrx is running a 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. The company also plans to explore INBRX-106 in combination with therapeutic cancer vaccines, citing observed clinical activity and T‑cell responses in HPV+ disease as justification for vaccine combination strategies and potential expansion into broader solid tumor indications.

What safety profile has been observed with INBRX-106 plus pembrolizumab so far?

In the Phase 2 HexAgon study, the combination of INBRX-106 and pembrolizumab was described as generally manageable. The most common treatment‑related adverse events were rash, fatigue and diarrhea, which were reported as predominantly low grade.

How can investors and stakeholders access Inhibrx’s discussion of these results?

Inhibrx will host a live webcast presentation on September 8, 2026, at 5:00 a.m. Pacific Time to discuss the results. The webcast will include a slide presentation of the data and is incorporated into the company’s investor deck, which is accessible via the investor section of its website at https://inhibrx.com/inhibrx-biosciences-inc-investors/.