Avenzo Therapeutics, Inc. (“Avenzo”), a clinical-stage biotechnology company developing next-generation oncology therapies, today announced that preliminary results from the Phase 1 portion of its ongoing Phase 1/2 ORION-1 study of AVZO-023, a selective and potentially best-in-class cyclin dependent kinase 4 (CDK4) inhibitor, will be presented as a poster at the 2026 San Antonio Breast Cancer Symposium (SABCS). The Symposium will take place December 8–11, 2026, in San Antonio, Texas.

The presentation will focus on preliminary safety, tolerability and efficacy results for AVZO-023 in combination with fulvestrant in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced or metastatic breast cancer.

Poster Presentation Details

Abstract Number: 2618

Presentation Number: P1-4-13

Presentation Title: Preliminary phase 1 results from ORION-1, a phase 1/2 study of AVZO-023 with endocrine therapy and/or AVZO-021 in HR+/HER2- metastatic breast cancer (mBC)

Date/Time: Wednesday, December 9, 2026, 12:30–2:00 p.m. CT

Location: Exhibit Hall, Henry B. Gonzalez Convention Center, San Antonio, Texas

About AVZO-023

AVZO-023 is a potentially best-in-class, oral, highly potent, and selective cyclin-dependent kinase 4 (CDK4) inhibitor in development for HR+/HER2- advanced or metastatic breast cancer. It is designed to inhibit CDK4/cyclin D-mediated signaling, a central driver of tumor cell proliferation, while sparing CDK6, whose inhibition is associated with hematologic toxicity. This selectivity may support improved tolerability and combination treatment with endocrine therapy and CDK2 inhibition. AVZO-023 is being evaluated in the Phase 1/2 ORION-1 study in combination with fulvestrant or letrozole, and in a triplet combination with AVZO-021, a selective CDK2 inhibitor, and fulvestrant. Avenzo holds exclusive global rights, excluding Greater China, from Allorion Therapeutics to develop, manufacture and commercialize AVZO-023.

About AVZO-021

AVZO-021 is an oral, highly potent, and selective cyclin-dependent kinase 2 (CDK2) inhibitor in development for HR+/HER2- advanced or metastatic breast cancer and other solid tumors. It is designed to target the cyclin E/CDK2 pathway, a key mechanism of resistance to CDK4/6 inhibitors. Its high selectivity over CDK1 may limit off-target toxicity and support use in combination regimens. Enrollment is complete in the Phase 1 portion of the study evaluating AVZO-021 as monotherapy and in combination with fulvestrant. AVZO-021 is also being evaluated in the Phase 1/2 ORION-1 study in a triplet combination with AVZO-023 and fulvestrant. The triplet is intended to target both a primary driver of tumor proliferation and a key mechanism of resistance to CDK4/6 inhibitors. Avenzo holds exclusive global rights, excluding Greater China, from Allorion Therapeutics to develop, manufacture and commercialize AVZO-021.

About Avenzo Therapeutics

Avenzo Therapeutics is a clinical-stage biotechnology company focused on developing next-generation oncology therapies for patients. The company’s pipeline includes potentially differentiated small molecules and bispecific antibody-drug conjugates (ADCs). Avenzo’s small molecule inhibitors, AVZO-021 and AVZO-023, are novel, highly potent and selective inhibitors of CDK2 and CDK4, respectively, which are key enzymes involved in cell cycle regulation. AVZO-021 is being evaluated in a Phase 1/2 study as monotherapy in advanced solid tumors and in combination with fulvestrant in HR+/HER2- metastatic breast cancer. AVZO-021 and AVZO-023 are being evaluated in the Phase 1/2 ORION-1 study in HR+/HER2- metastatic breast cancer, where AVZO-023 is administered in combination with endocrine therapy, with or without AVZO-021. Avenzo’s first ADC drug candidate, AVZO-1418, is a potentially differentiated EGFR/HER3 bispecific ADC that is being studied in the AVENTINE-1 Phase 1/2 study for the treatment of advanced solid tumors. Avenzo’s second ADC drug candidate, AVZO-103, is a potentially differentiated Nectin4/TROP2 bispecific ADC that is being studied in the BEACON-1 Phase 1/2 study for the treatment of advanced solid tumors. Avenzo is headquartered in San Diego, California. For more information, visit us at www.avenzotx.com or on LinkedIn.

Forward-Looking Statements

This press release contains forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995, including, without limitation, statements regarding: Avenzo’s expectations with respect to the presentation of data at the 2026 San Antonio Breast Cancer Symposium; the design, mechanism of action and potential benefits of AVZO-023 and AVZO-021, including with respect to selectivity, tolerability and ability to address resistance to CDK4/6 inhibitors; the timing, enrollment, design and progress of the ORION-1 study and Avenzo’s other ongoing and planned clinical trials, including the studies of AVZO-021 as monotherapy and in combination with fulvestrant, and the AVENTINE-1 and BEACON-1 studies of Avenzo’s ADC candidates AVZO-1418 and AVZO-103; the potential for Avenzo’s ADC candidates to be differentiated; Avenzo’s ability to continue to advance its potentially differentiated oncology pipeline; and other statements that are not historical facts. These statements are subject to a number of risks, uncertainties and assumptions, including, but not limited to: uncertainties associated with the clinical development and regulatory approval of product candidates, including potential delays in the commencement, enrollment and completion of clinical trials, and whether preliminary, interim or future data from such trials will support continued development or regulatory approval; uncertainties in obtaining successful clinical results for product candidates and unexpected costs that may result therefrom; risks related to Avenzo’s dependence on novel combination regimens that have not been validated in later-stage trials; risks related to Avenzo’s reliance on its collaborations and licenses with third parties, including Allorion Therapeutics, for the development of its product candidates; risks related to the inability of Avenzo to obtain sufficient additional capital to continue to advance its product candidates; and uncertainties regarding Avenzo’s ability to achieve its long-term goals and capitalize on opportunities. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties. You should not place undue reliance on these forward-looking statements, which are made only as of the date hereof or as of the dates indicated in the forward-looking statements. Avenzo expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in its expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.

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