Inhibrx Reports Interim Phase 2 Data for INBRX-106 in First-Line HNSCC; Initial Results Demonstrate Potential Costimulatory Benefit Over PD-1 Monotherapy

Inhibrx (Nasdaq: INBX) reported interim Phase 2 HexAgon data for INBRX-106 plus pembrolizumab in first-line PD-L1–high HNSCC.

Rhea-AI Summary

Inhibrx (Nasdaq: INBX) reported interim Phase 2 HexAgon data for INBRX-106 plus pembrolizumab in first-line PD-L1–high HNSCC. In 53 response-evaluable patients, the combination showed a 44.0% confirmed objective response rate versus 21.4% with pembrolizumab alone, including three complete responses versus none in control.

Combination treatment produced up to a 15-fold increase in peripheral CD8+ and CD4+ T-cell proliferation and a manageable safety profile without treatment-related deaths. Progression-free survival data are expected in Q4 2026, with a Phase 3 start planned for Q3 2026 and expansion into NSCLC studies.

Positive

• Confirmed objective response rate 44.0% vs 21.4% with pembrolizumab alone in evaluable patients
• Three complete responses with INBRX-106 combination vs zero with pembrolizumab monotherapy
• Up to 15-fold increase in CD8+ and CD4+ T-cell proliferation in combination arm
• Safety profile described as manageable with no treatment-related deaths reported
• Phase 3 HexAgon study planned to begin in Q3 2026
• Planned expansion into perioperative and metastatic NSCLC settings from 2026–2027

Negative

• Interim analysis based on 53 of 68 enrolled patients; 15 not yet evaluable
• Key efficacy endpoint progression-free survival not available until expected Q4 2026
• Most common treatment-related adverse events include rash, diarrhea, fatigue, infusion reactions
• Current data limited to PD-L1 CPS ≥ 20, metastatic or unresectable recurrent HNSCC population

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Key Figures

cORR combo arm: 44.0% cORR control arm: 21.4% cORR absolute increase: 22.6% +5 more

cORR combo arm

44.0%

INBRX-106 + pembrolizumab in preliminary confirmed response-evaluable HNSCC patients

cORR control arm

21.4%

Pembrolizumab monotherapy in preliminary confirmed response-evaluable HNSCC patients

cORR absolute increase

22.6%

Difference in confirmed ORR between combo and monotherapy arms

Complete responses

3 patients

Complete radiographic responses in INBRX-106 combination arm; none in control

Tumor shrinkage depth

>50%

Majority of responders in combo arm had target lesion shrinkage exceeding 50%

Systemic T-cell expansion

Up to 15-fold

Mean increase in peripheral CD8+ and CD4+ T-cell proliferation with combo

Trial enrollment

68 patients

Total randomized in Phase 2 portion of HexAgon first-line HNSCC study

Arm randomization

33 vs 35 patients

Patients assigned to combo vs control arms in Phase 2 HexAgon

Previous Clinical trial Reports

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Key Terms

objective response rate, cORR, pd-1, pd-l1, +4 more

8 terms

objective response rate medical

"achieved a 44.0% confirmed Objective Response Rate (cORR)"

The objective response rate (ORR) is the percentage of patients in a clinical trial whose tumors measurably shrink or disappear according to preset rules. Investors use it as a quick, objective signal of a drug’s ability to produce a clear treatment effect—like counting how many plants visibly respond after applying a new fertilizer—and higher ORR can improve odds of regulatory approval, commercial success, and company valuation.

cORR medical

"achieved a 44.0% confirmed Objective Response Rate (cORR)"

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.

pd-1 medical

"costimulatory benefit Over PD-1 Monotherapy"

PD-1 is a protein found on certain immune cells that acts like a brake, signaling the immune system to slow down and avoid damaging healthy tissue. Drugs that block PD-1 release that brake so immune cells can better attack cancer cells; because such therapies can produce large clinical benefits, regulatory approvals, trial outcomes, pricing and market uptake for PD-1 drugs can materially affect a drugmaker’s prospects and investor returns.

pd-l1 medical

"PD-L1 positive (CPS ≥ 20) metastatic or unresectable recurrent"

PD-L1 is a protein found on the surface of some cells that acts like a stop sign for the immune system, telling certain immune cells to back off. It matters to investors because many cancer drugs and diagnostic tests target or measure PD-L1 to unlock immune responses or predict which patients will benefit, affecting clinical success, regulatory approval, and potential sales in the oncology market.

progression-free survival medical

"The progression-free survival data from the Phase 2 portion"

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.

non-small cell lung cancer medical

"initiating a study in the perioperative setting in non-small cell lung cancer (NSCLC)"

A broad category of lung tumors that grow from the cells lining the airways and make up the majority of lung cancer cases; it includes several subtypes that behave and respond to treatment differently, like different models of the same car family. It matters to investors because its large patient population and variety of treatment options — surgery, traditional chemo, targeted drugs and immunotherapies — create major markets where clinical trial results, drug approvals or changing treatment guidelines can quickly affect a company’s revenue and stock value.

checkpoint inhibitors medical

"to potentially improve the efficacy of checkpoint inhibitors"

Checkpoint inhibitors are drugs that help the immune system recognize and attack cancer cells by blocking certain proteins that normally keep immune responses in check. They act like brakes being released on the immune system, allowing it to target tumors more effectively. These medicines are important for investors because they represent a promising area of cancer treatment with growing research, development, and commercial potential.

car-ts medical

"combinations with agents that could benefit from T-cell costimulation, such as vaccines, T-cell engagers, and CAR-Ts."

CAR‑Ts are cancer treatments made by taking a patient’s immune cells, reprogramming them in a lab to recognize a specific marker on tumor cells, and returning them to the body to seek and destroy those cancer cells. They matter to investors because they represent a high‑growth, high‑risk area of medicine: potential for transformative, high‑value therapies and sales, but also heavy development and manufacturing costs, regulatory hurdles, and variable long‑term effectiveness — like funding a startup that could either revolutionize an industry or face steep technical and market barriers.

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• Interim analyses show INBRX-106 + pembrolizumab achieved a 44.0% confirmed Objective Response Rate (cORR): In the preliminary confirmed response-evaluable population, the INBRX-106 + pembrolizumab combination achieved a cORR of 44.0% versus 21.4% with pembrolizumab alone, representing a 22.6% absolute increase in cORR.
• Superior depth of response: Responding patients in the combination arm demonstrated deeper tumor reductions overall, with the majority achieving target lesion shrinkage exceeding 50%; notably, three patients achieved a complete radiographic response.
• Up to 15-fold mean increase in systemic T-Cell expansion: Peripheral blood analysis showed robust CD8+ and CD4+ T-cell proliferation in combination-treated patients, providing mechanistic support for the observed clinical activity.
• Manageable safety profile: The combination demonstrated a manageable preliminary safety profile consistent with that expected from an immunotherapy combination.

SAN DIEGO, May 11, 2026 /PRNewswire/ -- Inhibrx Biosciences, Inc. (Nasdaq: INBX) ("Inhibrx" or the "Company"), a clinical-stage biopharmaceutical company focused on developing novel biologic therapeutic candidates, today announced positive interim results from the randomized, first-line Phase 2 portion of the HexAgon study. The trial evaluated 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).

HNSCC was selected as a proof-of-concept indication, as PD-1 monotherapy is active in this tumor type but leaves significant room for improvement. The trial design was modeled after KEYNOTE-048, focusing on patients with high PD-L1 expression (CPS ≥ 20) in order to further sharpen the ability to detect a treatment effect above checkpoint inhibition alone. A clear signal of added benefit in this study design would support INBRX-106's potential to enhance checkpoint inhibitor efficacy across checkpoint inhibitor-sensitive indications.

The Phase 2 portion of the HexAgon study enrolled 68 patients: 33 randomized to the combination arm and 35 to the control arm. Baseline prognostic factors are largely balanced between both arms and the study is being conducted at over 80 sites in the United States, Europe and Asia. Today, the Company presented preliminary data from 53 patients (25 in the INBRX-106 combination arm and 28 in the control arm) with a data cutoff of May 7, 2026, representing the evaluable population for confirmed response, defined as patients who had either experienced confirmed disease progression or death, or completed at least two on-study tumor assessments. The remaining 15 patients in the overall population across both arms had not yet reached the maturity threshold for response confirmation or were not evaluable at the time of this data cut and were therefore not included in this analysis. Active unconfirmed responses and ongoing tumor increases/reductions are present in both arms, and these patients are expected to contribute to the final efficacy dataset in a subsequent update.

In the evaluable population, 11 out of 25 patients (44.0%) in the INBRX-106 combination arm achieved a confirmed objective response, compared with 6 out of 28 patients (21.4%) in the control arm. This represents a 22.6% absolute increase in confirmed responses. Three complete responses were observed in the INBRX-106 combination arm, reflecting tumor clearance, while no complete responses were observed with pembrolizumab alone. Complete responses in first-line HNSCC remain uncommon and are generally associated with more durable outcomes.

These clinical findings were supported by pharmacodynamic data, which showed up to a 15-fold increase in peripheral CD8+ and CD4+ T-cell proliferation and up to a four-fold increase in activation in INBRX-106 combination-treated patients compared with up to 2.5-fold and 1.5-fold increases, respectively, in those receiving pembrolizumab alone. The observation of robust systemic T-cell expansion and activation in combination-treated patients, alongside the clinical activity observed in this arm, is consistent with the expected mechanism of action of INBRX-106 as a potent T-cell costimulator.

The combination of INBRX-106 and pembrolizumab was generally manageable, with a safety profile consistent with the addition of an active immunostimulatory agent to checkpoint blockade. The most common treatment-related adverse events were rash, diarrhea, fatigue, and infusion-related reactions, which were predominantly low-grade. No treatment-related deaths were reported in either arm.

"We are greatly encouraged by these early clinical results," said Mark Lappe, Chief Executive Officer of Inhibrx. "These data, coupled with the clear evidence of T-cell expansion and superior depth of response, give us confidence that INBRX-106 could be the first costimulatory agent to fundamentally shift the efficacy ceiling of immunotherapy, and open the door to combinations with new modalities that could be enhanced by OX40 agonism."

Next Steps

The progression-free survival data from the Phase 2 portion of the HexAgon study are expected to become available in the fourth quarter of 2026. The Company plans to begin the Phase 3 portion of the HexAgon study during the third quarter of 2026.

Based on these promising early results, the Company also aims to evaluate INBRX-106 across broader indications to potentially improve the efficacy of checkpoint inhibitors. This strategy includes initiating a study in the perioperative setting in non-small cell lung cancer (NSCLC) later this quarter. The Company believes OX40 agonism has the greatest potential to drive cure in earlier-stage disease settings, where patients typically retain a more active and responsive immune system. In addition, the Company is beginning to plan for expansion into the front-line metastatic NSCLC setting, with studies expected to begin in 2027. Outside of combination with checkpoint inhibitors, the Company plans to explore combinations with agents that could benefit from T-cell costimulation, such as vaccines, T-cell engagers, and CAR-Ts.

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. To date, over 175 patients have been treated with INBRX-106.

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; the clinical development of INBRX-106, including expected enrollment in the expansion cohort, data readouts, regulatory submissions and interactions, and the timing thereof; any presumption that topline, interim or preliminary data will be representative of final data or data in later clinical trials, including data from the remaining 15 patients in the overall population for the Phase 2 trial for INBRX-106 in first-line HNSCC; Inhibrx's plans to evaluate INBRX-106 across broader indications and to explore combinations with other therapies; Inhibrx's plans to expand into the front-line metastatic NSCLC setting, with studies expected to begin in 2027; and Inhibrx's plans to begin the Phase 3 portion of the HexAgon study during the third quarter of 2026. 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; 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

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What Phase 2 results did Inhibrx (INBX) report for INBRX-106 in first-line HNSCC?

Inhibrx reported interim Phase 2 HexAgon data showing INBRX-106 plus pembrolizumab achieved higher confirmed responses than pembrolizumab alone. According to Inhibrx, the combination reached a 44.0% confirmed objective response rate in evaluable patients versus 21.4% with pembrolizumab monotherapy.

How did the INBRX-106 combination compare with pembrolizumab alone in objective response rate for INBX?

The INBRX-106 plus pembrolizumab arm showed a higher confirmed objective response rate than pembrolizumab alone. According to Inhibrx, 44.0% of evaluable combination patients responded (11/25) compared with 21.4% (6/28) in the control arm, a 22.6% absolute difference.

What T-cell activation effects were observed with INBRX-106 in the HexAgon study for INBX?

INBRX-106 plus pembrolizumab was associated with greater systemic T-cell expansion and activation than pembrolizumab alone. According to Inhibrx, combination-treated patients showed up to a 15-fold increase in CD8+ and CD4+ proliferation and up to four-fold activation, versus lower increases in control patients.

What safety profile did INBRX-106 show in first-line HNSCC according to Inhibrx (INBX)?

The INBRX-106 and pembrolizumab combination showed a manageable preliminary safety profile consistent with immunotherapy combinations. According to Inhibrx, common treatment-related adverse events included rash, diarrhea, fatigue, and infusion reactions, which were mainly low-grade, and no treatment-related deaths occurred in either trial arm.

What are the next steps for the INBRX-106 HexAgon program and INBX timeline?

Inhibrx plans to continue development of INBRX-106 based on interim HexAgon data. According to Inhibrx, progression-free survival results are expected in Q4 2026, a Phase 3 HexAgon trial should start in Q3 2026, and additional NSCLC studies are planned from 2026 to 2027.

Will Inhibrx (INBX) test INBRX-106 beyond head and neck cancer?

Yes, Inhibrx aims to evaluate INBRX-106 in additional tumor settings beyond HNSCC. According to Inhibrx, plans include a perioperative non-small cell lung cancer study starting later this quarter and front-line metastatic NSCLC trials expected to begin in 2027, plus combinations with other T-cell–targeting agents.