FDA Grants Fast Track Designation for Ambrx’s ARX517 for the Treatment of Metastatic Castration-Resistant Prostate Cancer

SAN DIEGO, July 19, 2023 (GLOBE NEWSWIRE) -- Ambrx Biopharma Inc., Ambrx (or the “Company”) (NASDAQ: AMAM), today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to Ambrx’s proprietary anti-PSMA antibody-drug conjugate (ADC) investigational therapy, ARX517, for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC) upon progression on an androgen receptor pathway inhibitor. Fast Track designation is a process designed to facilitate the development and expedite the review of drugs which may demonstrate substantial improvement over available therapy for serious conditions with unmet medical need.

“Receiving Fast Track designation from the FDA reinforces Ambrx’s belief in ARX517 as a potential novel treatment for mCRPC and underscores the urgent need for improved treatment options for patients at this advanced stage of prostate cancer,” said Sandra Aung, Ph.D., Chief Clinical Officer of Ambrx.  

ARX517 is currently being studied in APEX-01, a Phase 1/2, first-in-human, open label dose escalation and dose expansion trial enrolling patients with mCRPC whose tumors have progressed on at least two prior FDA approved treatments for prostate cancer, and patients must have one of the following three criteria met: i) PSA progression defined by a minimum of 2 rising PSA values; or ii) radiographic progression by RECIST v 1.1 or iii) disease progression by the presence of new bone lesions.   APEX-01 is the only ongoing clinical trial in the United States targeting PSMA with an ADC.

Daniel J. O'Connor, Chief Executive Officer of Ambrx added: "This Fast Track designation represents a significant milestone for Ambrx. Enabled by our expanded genetic code site-specific conjugation technology, ARX517 has the potential to be a more effective and tolerable treatment option for these patients, and we are planning to present updated preliminary data from APEX-01 at a major medical meeting this fall.”

ARX517 is an antibody-drug conjugate composed of a fully humanized anti-PSMA mAb linked to AS269, a proprietary and potent microtubule inhibitor. Prostate-specific membrane antigen (PSMA) is highly expressed (>89%) in mCRPC and has been shown to be a validated therapeutic target. Upon binding to PSMA on the surface of cancer cells, ARX517 is internalized and pAF-AS269, its cancer cell killing payload, is released following lysosomal metabolism. ARX517’s site-specific linkage, non-cleavable linker and stable conjugation chemistry, is enabled by Ambrx’s proprietary expanded genetic code technology which was recently featured in . ARX517’s linker has exceptional stability, and the resulting ADC exhibits a homogenous drug-to-antibody ratio and mAb-like biophysical properties. Therefore, Ambrx believes ARX517 can promote highly specific tumor cell killing with minimal off-target toxicity. ARX517 has the potential to be a first- and best-in-class anti-PSMA ADC addressing the high unmet medical need in mCRPC.

About Ambrx Biopharma Inc.

Ambrx is a clinical stage biopharmaceutical company using an expanded genetic code technology platform to discover and develop 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 antibody-drug conjugate (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 Ambrx routinely posts information that may be important to investors on its website.

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. 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 and marketing approval of novel therapeutics, including potential delays in clinical trials and regulatory submissions and the fact that future clinical trial results/data may not be consistent with interim, initial or preliminary results/data or results/data 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 Quarterly Report on Form 10-Q filed with the SEC on May 11, 2023, and elsewhere in Ambrx’s filings and reports with the SEC, including the prospectus supplement to be filed in connection with the Offering. 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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Source: Ambrx Biopharma, Inc.