Whitehawk Therapeutics Presents Real‑World Analysis Confirming SEZ6 as a Highly Expressed, Clinically Relevant Target for SCLC and Other Neuroendocrine Tumors at ASCO 2026

SEZ6 expression exceeds that of approved and emerging ADC targets in SCLC  

SEZ6 expression is positively correlated with DLL3 expression across neuroendocrine carcinomas, indicating potential for combination

Findings support Whitehawk's development of SEZ6-directed ADC, HWK-206, with an IND submission expected mid-2026

MORRISTOWN, N.J., May 30, 2026 /PRNewswire/ -- Whitehawk Therapeutics, Inc. (Nasdaq: WHWK), a clinical-stage oncology therapeutics company applying advanced technologies to established tumor biology to efficiently deliver improved antibody drug conjugate (ADC) cancer treatments, today announced the presentation of a real world analysis supporting the therapeutic potential of targeting seizure related homolog protein 6 (SEZ6) with a next-generation ADC for the treatment of neuroendocrine tumors, including small cell lung cancer (SCLC). These data will be presented in a poster at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, being held May 29-June 2, 2026, in Chicago, Illinois.

SEZ6 is a cell surface transmembrane protein involved in neuronal development that is primarily expressed in central nervous system (CNS) tissues. A large-scale RNA analysis demonstrated that SEZ6 is highly expressed across SCLC and other tumors of neuroendocrine origin. In SCLC, expression exceeds other approved and emerging ADC targets. SEZ6 expression is positively correlated with DLL3, indicating the potential for combination approaches with DLL3-targeted therapies. Together, these data support its potential as a clinically meaningful ADC target and reinforce the rationale for clinical development of HWK-206.

"SEZ6 demonstrates a compelling expression profile across SCLC and other neuroendocrine malignancies. In SCLC, it has levels of expression that are consistently high across disease stages and metastatic settings," said Afshin Dowlati, MD, University Hospitals Seidman Cancer Center and Case Western Reserve University. "The magnitude of SEZ6 expression relative to other therapeutic targets, along with its enrichment in neuroendocrine‑high SCLC subtypes, supports its potential as an ADC target."

Key Findings Include:

• SEZ6 is highly expressed in SCLC and other tumors of neuroendocrine origin.
• Expression exceeds other established and emerging ADC targets.
  • SCLC – SEZ6 expression was at least 3-fold higher than HER2, B7-H3, DLL3, PD-L1 and PD-1.
  • Prostate neuroendocrine carcinoma – SEZ6 expression was 2- to 6-fold higher than B7-H3, DLL3 and TROP2.
• Among SCLC molecular subtypes, SEZ6 expression is highest in SCLC-A and SCLC-N, which accounts for ~90% of subtypes and are characterized by high expression of neuroendocrine transcription factors.
• Expression is high across SCLC disease stages and metastatic status, supporting potential relevance across treatment settings.
• Correlative expression in DLL3 supports combination strategies.

HWK-206 utilizes a dual epitope binding, or biparatopic, approach which can potentially improve binding and internalization of the ADC. In preclinical models, HWK-206 has demonstrated the potential to outperform other single epitope ADCs in development. An Investigational New Drug application to evaluate HWK-206 in SCLC and neuroendocrine tumors is expected to be submitted in mid-2026, with a Phase 1 start planned in Q3 2026.

"This real-world characterization of SEZ6 expression across small cell lung cancer and other neuroendocrine tumors reinforce our conviction in SEZ6 as a clinically meaningful target for ADC development," said Margaret Dugan, MD, Chief Medical Officer of Whitehawk Therapeutics. "These findings add to the body of evidence supporting our biparatopic SEZ6-directed ADC, HWK-206, and its potential to have a meaningful impact on patients with SCLC and neuroendocrine tumors."

Poster Presentation Details:

Title: Real-world characterization of SEZ6, a transmembrane protein expressed in various solid tumors
Poster: 219
Abstract: 3082
Presenter: Afshin Dowlati, MD, University Hospitals Seidman Cancer Center and Case Western Reserve University
Date & Time: May 30^th, 2026, 1:30 - 4:30 PM CDT

The analysis was conducted as part of a previously announced collaboration between Whitehawk and Tempus AI. The posters will be accessible on the Presentations page of the Investors & News section of the Company's website at www.whitehawktx.com.

About Whitehawk Therapeutics
Whitehawk Therapeutics is a clinical-stage oncology therapeutics company applying advanced technologies to established tumor biology to efficiently deliver improved cancer treatments. Whitehawk's advanced three-asset ADC portfolio is engineered to overcome the limitations of first-generation predecessors to deliver a meaningful impact for patients with difficult-to-treat cancers. These assets are in-licensed from WuXi Biologics under an exclusive development and global commercialization agreement. More information on the Company is available at www.whitehawktx.com and connect with us on LinkedIn. Any references to the Company's website or other online resources are provided solely for convenience and are not incorporated by reference into this press release. Investors should rely only on the information contained in this press release and the Company's filings with the Securities and Exchange Commission.

Forward Looking Statements
This press release contains certain forward-looking statements regarding the business of Whitehawk Therapeutics that are not a description of historical facts within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements are based on the Company's current beliefs and expectations and may include, but are not limited to, the anticipated timing of the Company's development of HWK-206, including the expected submission of Investigational New Drug applications for HWK-206 in mid-2026; statements relating to expectations regarding the beneficial characteristics, optimized ADC design features, safety, efficacy, and therapeutic effects of HWK-206; the size and opportunity of the potential targeted markets with respect to HWK-206; and the sufficiency of the Company's existing capital resources and the expected timeframe to fund its future operating expenses and capital expenditure requirements. Actual results could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, uncertainties associated with preclinical and clinical development of the Company's portfolio, including failure to demonstrate the efficacy of the such portfolio in preclinical and clinical studies; the risk that unforeseen adverse reactions or side effects may occur in the course of testing of the ADC assets; and risks related to the Company's estimates regarding future expenses, capital requirements and need for additional financing.

Additional risks and uncertainties that could cause actual outcomes and results to differ materially from those contemplated by the forward-looking statements are included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2025, including under the caption "Item 1A. Risk Factors," and in Whitehawk's subsequent Quarterly Reports on Form 10-Q, and elsewhere in Whitehawk's reports and other documents that Whitehawk has filed, or will file, with the SEC from time to time and available at www.sec.gov.

All forward-looking statements in this press release are current only as of the date hereof and, except as required by applicable law, Whitehawk undertakes no obligation to revise or update any forward-looking statement, or to make any other forward-looking statements, whether as a result of new information, future events or otherwise. All forward-looking statements are qualified in their entirety by this cautionary statement. This cautionary statement is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

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SOURCE Whitehawk Therapeutics, Inc.