- ARX305 is being developed as an anti-CD70 antibody drug conjugate for treatment of a broad range of solid and hematologic tumors -

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 it received a “Study May Proceed” letter from the U.S. Food and Drug Administration (FDA) related to an Investigational New Drug (IND) application for ARX305, an antibody drug conjugate (ADC) designed to target CD70 to treat a broad range of solid and hematologic tumors such as renal cell carcinoma. ARX305 is the third ADC developed by Ambrx on its proprietary Engineered Precision Biologics platform that has received IND clearance.

The clinical study cleared by the FDA, ARX305-01, is a first in human, Phase 1, multicenter, open-label, dose-escalation, and dose-expansion study to evaluate the safety, pharmacokinetics and preliminary anti-tumor activity of ARX305 in adults with clear cell renal cell carcinoma who are resistant or refractory to prior standard therapies.

ARX305 is an anti-CD70 ADC designed to target cancer cells displaying CD70, a protein expressed on a broad range of tumors including renal cell carcinoma, nasopharyngeal cancers, multiple myeloma, non-Hodgkin’s lymphoma and acute myeloid leukemia. Ambrx previously licensed the rights to develop and commercialize ARX305 in China to NovoCodex Pharmaceuticals Ltd. (NovoCodex).

“I am pleased with the milestones that we have reached on the development of antibody drug conjugates, marked by the filing and clearance of the IND application for ARX305, our third ADC program to reach this stage of development,” said Feng Tian, Ph.D., Chairman of the Board, President, and CEO of Ambrx. “As we continue to explore potential indications for Ambrx’s proprietary ADC technology, the progression of ARX305 towards clinical trials targeting patients with various CD70 expressing tumors reinforces our confidence in the broad application of our platform.”

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.

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 its product candidates, clinical development and strategic plans, the timing of future events, and anticipated upcoming milestones. 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 studies 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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