Ambrx Biopharma Inc. and Quantum Leap Healthcare Collaborative™ Announce the Inclusion of ARX788 in the I-SPY 2.2 Phase 2 Adaptive Clinical Trial for Breast Cancer

Quantum Leap Healthcare Collaborative™ (Quantum Leap) and Ambrx Biopharma Inc., or Ambrx, (NYSE: AMAM), a clinical stage biopharmaceutical company using an expanded genetic code technology platform to create Engineered Precision Biologics, today announced the selection of Ambrx’s antibody drug conjugate (ADC) ARX788 for a new investigational treatment arm in the I-SPY 2.2 TRIAL for the treatment of HER2-positive breast cancer in the neoadjuvant setting. Sponsored by Quantum Leap, the I-SPY 2.2 TRIAL is a continuation of the I-SPY 2 TRIAL that seeks to create personalized treatments by adapting therapies for each patient to optimize the clinical outcome.

“We are particularly excited about this collaboration,” stated Dr. Laura J. Esserman, MD, MBA, Director of the Breast Care Center at the UCSF Helen Diller Family Comprehensive Cancer Center, and Principal Investigator of I-SPY Family of Trials. “We hope this will usher in an era of more targeted, effective and less toxic therapies for people with HER2-positive breast cancers, leveraging decades of investment in science and drug development, and delivering better treatment to patients when they need it most. This is the right drug, for the right patient at the right time.”

I-SPY 2.2 is an adaptive Phase 2 clinical trial that evaluates emerging targeted agents, allowing those agents to either be combined with less toxic chemotherapeutic regimens or to replace cytotoxic chemotherapy entirely. ARX788 will be evaluated as a monotherapy, and in combination with the PD-1 targeting checkpoint inhibitor cemiplimab, in HER2-positive early-stage breast cancer in the neoadjuvant setting. Ambrx anticipates the ARX788 arms to begin enrolling patients in May 2022.

Quantum Leap, sponsor of the I-SPY 2.2 TRIAL, leads a pre-competitive consortium that includes the U.S. Food & Drug Administration (FDA), industry, patient advocates, philanthropic sponsors, and clinicians from more than 16 major U.S. cancer research centers.

“I am thrilled that Quantum Leap has selected Ambrx’s antibody drug conjugate, ARX788, to be evaluated in the I-SPY 2.2 TRIAL,” said Feng Tian, Ph.D., Chairman of the Board, President, and CEO of Ambrx. “We are encouraged by the favorable anti-tumor activity and safety profile of ARX788 for the treatment of early-stage breast cancer. It may provide a less toxic treatment option for patients through the precision conjugation of cytotoxic payloads targeting HER2 receptors. I look forward to collaborating with Quantum Leap and exploring the potential of our antibody drug conjugate in enabling effective chemo-free therapeutic treatments to patients.”

ARX788 is an anti-HER2 antibody drug conjugate (ADC) that is being studied broadly in breast cancer, gastric/GEJ cancer and other solid tumors. ARX788 is a homogeneous and highly stable ADC that maximizes potential anti-tumor activity by optimizing the number and position of its payloads and the chemical bonds that conjugate the payloads to the antibody. The United States Food and Drug Administration (FDA) has granted ARX788 the Fast Track Designation for the treatment of HER2-positive metastatic breast cancer.

About Ambrx Biopharma Inc. (Ambrx)

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), bispecifics, targeted immuno-oncology therapies, novel cytokines to modulate the immune system, and long-acting therapeutic peptides for metabolic and cardiovascular disease. Ambrx is advancing a robust portfolio of clinical and preclinical programs designed to optimize efficacy, safety and ease of use, in multiple therapeutic areas, including its lead product candidate ARX788. In addition, Ambrx has clinical collaborations with multiple partners, for drug candidates generated using Ambrx technology. For more information, please visit www.ambrx.com.

About the I-SPY TRIALs

The I-SPY 2 TRIAL (Investigation of Serial studies to Predict Your Therapeutic Response with Imaging And moLecular analysis) was designed to rapidly screen promising experimental treatments and identify those most effective in specific patient subgroups based on molecular characteristics (biomarker signatures). The trial is a unique collaborative effort by a consortium that includes the Food and Drug Administration (FDA), industry, patient advocates, philanthropic sponsors, and clinicians from more than 20 major U.S. cancer research centers. Under the terms of the collaboration agreement, Quantum Leap Healthcare Collaborative is the trial sponsor and manages all study operations. For more information, visit www.ispytrials.org.

About Quantum Leap Healthcare Collaborative

Quantum Leap Healthcare Collaborative is a 501(c)(3) charitable organization established in 2005 as a collaboration between medical researchers at University of California, San Francisco and Silicon Valley entrepreneurs. Our mission is to integrate high-impact research with clinical processes and systems technology, resulting in improved data management and information systems, greater access to clinical trial matching and sponsorship, and greater benefit to providers, patients and researchers. Our goal is to improve and save lives. Quantum Leap provides operational, financial, and regulatory oversight to the I-SPY Trials. For more information, visit www.QuantumLeapHealth.org.

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 “anticipate,” believe,” “estimate,” “expect,” “intend,” “plan,” “project,” “may,” “will,” “could,” “should,” “seek,” “potential” and similar expressions, and include, without limitation, express or implied statements regarding Ambrx’s beliefs and expectations regarding the advancement and potential benefits of ARX788, clinical development and strategic plans for ARX788, and the timing of program updates and milestones related to ARX788. 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 impact of the COVID-19 pandemic 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 registration statement on Form F-1 filed with the United States Securities and Exchange Commission (SEC) on June 14, 2021, and elsewhere in Ambrx’s filings and reports with the SEC. Forward-looking statements contained in this announcement 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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