Ambrx Biopharma to Host Analyst and Investor Day to Discuss ARX788 in Breast Cancer and ARX517 in Prostate Cancer

• Virtual presentation to take place on February 24, 2023 at 12:00pm ET
• Event will feature discussions regarding ARX788, Ambrx’s proprietary anti-HER2 targeting ADC, from key opinion leaders in breast cancer, Hope S. Rugo, M.D., FASCO, and Paula R. Pohlmann, M.D., M.S., Ph.D.
• Data update for APEX-01, a first-in-human study evaluating the safety and anti-tumor activity of ARX517, Ambrx’s proprietary anti-PSMA ADC, in prostate cancer patients will also be provided

​Ambrx Biopharma Inc., or Ambrx, (NYSE: AMAM), a clinical stage biopharmaceutical company using its proprietary Engineered Precision Biologics (EPBs) platform to create antibody drug conjugates (ADCs), today announced that it will host a virtual analyst and investor day on February 24 from 12:00pm – 1:00pm ET.

The event will feature discussions from oncology experts Hope S. Rugo, M.D., FASCO, (Professor of Hematology and Oncology, Director of Breast Oncology and Clinical Trials at the University of California, San Francisco), and Paula R. Pohlmann, M.D., M.S., Ph.D., (MD Anderson Cancer Center).

Dr. Rugo is a co-investigator on Ambrx’s ACE-Breast-03 clinical trial, a Phase 2 study of ARX788, Ambrx’s proprietary anti-HER2 targeting ADC, in patients with HER2-positive metastatic breast cancer whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens. Dr. Rugo will discuss the current treatment landscape and unmet medical need for patients with HER2 positive breast cancer, her clinical experience with ARX788 and the potential treatment solution that ARX788 may provide in the post-Enhertu HER2 positive metastatic breast cancer patient population.

Dr. Pohlmann is an investigator on I-SPY 2.2, where ARX788 is currently being evaluated as a neoadjuvant breast cancer treatment and Dr. Pohlmann will provide an overview of I-SPY 2.2 and discuss ARX788’s participation in the study. The I-SPY series of trials are changing the way new treatments are developed for breast cancer, helping make new, better and more personalized treatments, available faster. At the heart of the I-SPY program is the ground-breaking I-SPY 2.2 platform trial for neoadjuvant treatment of locally advanced breast cancer.

The Ambrx management team will also provide a data update for APEX-01 (NCT04662580), a first-in-human multicenter, dose escalation and dose expansion study evaluating the safety, pharmacokinetics, and preliminary anti-tumor activity of ARX517, Ambrx’s proprietary, fully humanized anti-PSMA ADC in prostate cancer patients who have progressed on at least two prior FDA-approved treatments.

A live question and answer session will follow the formal presentations.

Ambrx’s Analyst and Investor Day will be a virtual event webcast for the capital markets community, media, individual investors and other interested parties. All attendees must register for the event at https://lifesci.events/AmbrxReg. A replay of the event will be available on the Investor Relations section of Ambrx website (www.ambrx.com) after the event. Corresponding presentation materials will also be available for download at the Company's website following the event.

About Ambrx Biopharma Inc.

Ambrx is a clinical stage biopharmaceutical company using an expanded genetic code technology platform to discover and develop Engineered Precision Biologics. These include next generation antibody drug conjugates (ADCs) and other engineered therapies to modulate the immune system. Ambrx is advancing a focused portfolio of clinical and preclinical programs designed to optimize efficacy and safety in multiple cancer indications, including ARX517, its proprietary ADC targeting the prostate-specific membrane antigen (PSMA) and ARX788, its proprietary ADC targeting HER2. In addition, Ambrx has preclinical and clinical collaborations with multiple partners on drug candidates generated using Ambrx technology. Ambrx spun out of The Scripps Research Institute in 2003 and has several other product candidates involving ADCs and other aspects of Ambrx’s protein engineering technology. For more information, please visit www.ambrx.com.

Forward-Looking Statements

This press release includes certain “forward-looking statements” intended to qualify for the “safe harbor” from liability established by the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements may be identified by the words “intend,” “plan,” and similar expressions, and include, without limitation, express or implied statements regarding Ambrx’s clinical trial and product candidate plans and strategy. Forward-looking statements are based on Ambrx’s current expectations and are subject to inherent uncertainties, risks and assumptions that are difficult to predict. Factors that could cause actual results to differ include, but are not limited to, those risks and uncertainties associated with: the continuing impact of the COVID-19 pandemic and other public health-related risks and events on Ambrx’s business, operations, strategy, goals and anticipated milestones; Ambrx’s ability to execute on its strategy including with respect to the timing of its R&D efforts, initiation of clinical trials and other anticipated milestones; risks associated with development of novel therapeutics, including potential delays in clinical trials and regulatory submissions and the fact that future clinical trial results may not be consistent with preliminary results or results from prior preclinical studies or clinical trials; Ambrx’s ability to fund operations as anticipated; and the additional risks and uncertainties set forth more fully under the caption “Risk Factors” in Ambrx’s Annual Report on Form 20-F filed with the SEC on April 26, 2022, and elsewhere in Ambrx’s filings and reports with the SEC. Forward-looking statements contained in this press release are made as of this date, and Ambrx undertakes no duty to publicly update or revise any forward looking statements, whether as a result of new information, future events or otherwise, except as may be required under applicable law.

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