Clinical Trials

Ambrx, along with its partners, is evaluating Engineered Precision Biologics in clinical trials around the world, including trials for its antibody drug conjugates in the United States.


APEX-01 (ARX517, anti-PSMA ADC)

This is a Phase 1, multicenter, dose escalation and dose expansion study to evaluate the safety, pharmacokinetics, and preliminary anti-tumor activity of ARX517 in adult subjects whose advanced solid tumor failed prior standard therapies. ARX517 is an antibody drug conjugate consisting of a humanized anti-PSMA monoclonal antibody covalently conjugated to two proprietary microtubule-disrupting toxins AS269. The study includes 2 parts: a dose-escalation part and a dose-expansion part.

We have active sites in the U.S.: California, Texas, Georgia, Indiana, Michigan, Missouri, New Jersey, Nebraska, Washington, Virginia, New Mexico, Nevada, New York, Maryland, and Oregon.

For trial description, please see: NCT04662580

Or email:

ACE-PAN TUMOR-01 (ARX788, anti-HER2 ADC)

ACE-Pan tumor-01 is an open-label dose-escalation/dose expansion study on the effectiveness of ARX788 in patients with advanced cancers with HER2 expression. ARX788 is a conjugate of a HER2 targeted antibody with two cytotoxic payloads site-specifically conjugated. It is designed to form a highly stable covalent bond and kill tumor cells only upon entry into the cell – potentially limiting effects on healthy tissue.

Phase 1b is designed to assess anticancer activity and safety in HER2-low breast cancer, HER2-positive breast cancer, HER2-positive gastric cancer, and other HER2-mutated or amplified/over-expressed solid tumors. We are currently recruiting patients in the United States and Australia.

For trial description, please see: NCT03255070

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ACE-Breast-03 (ARX788, anti-HER2 ADC)

This is a Phase 2 study of ARX788 in subjects with advanced HER2 positive breast cancer who were previously treated with T-DM1, and/or T-DXd, and/or tucatinib-containing regimens in the metastatic setting.

We are recruiting patients in the U.S., Canada, Australia, Asia, Brazil, and Europe (Germany, Switzerland, UK, France, Italy, Portugal, Spain, Belgium, and Czech Republic).

For further information, please see: NCT04829604

Or email:

About ARX788: The FDA granted ARX788 Fast-Track Designation for the treatment of HER2-positive metastatic breast cancer in December 2020. Updated ARX788 clinical data was presented as Spotlight Poster Discussion (PD8-04) at the 2021 San Antonio Breast Cancer Symposium (SABCS), in December 2021.


At Ambrx, we are committed to developing products that bring new, innovative therapies to patients, such as ARX788 and ARX517.

At this time, Ambrx does not offer an expanded access program and is not accepting expanded access requests for investigational products, such as ARX788 and ARX517. Ambrx’ current focus and priority is to complete the product development program for its investigational products, such as ARX788 and ARX517, to obtain the required safety and efficacy data needed for regulatory approval. We believe that focusing our resources on our clinical trial programs is the best path forward to bring our investigational products to patients as quickly and safely as possible. Patients may gain access to our clinical-stage investigational products, such as ARX788 and ARX517, by participating in our clinical trials. If you would like to learn more about Ambrx’ clinical trials, please view the links above within

If you have additional questions about Ambrx’ expanded access policy, please email us at

As we continue to develop investigational products, we will review our expanded access policy for investigational products and may make updates to this policy. For more information about expanded access in the U.S., please visit the FDA website at