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ARX788 treatment for HER2-positive metastatic breast cancer

A Global, Phase 2 Study of ARX788 in HER2-positive Metastatic Breast Cancer Patients Who Were Previously Treated With T-DXd

Phase 2 Interventional Ambrx, Inc. · NCT04829604

This study is testing if a new treatment called ARX788 can help people with HER2-positive metastatic breast cancer who have already been treated with another medication.

Quick facts

PhasePhase 2
Study typeInterventional
Enrollment71 (estimated)
Ages18 Years and up
SexAll
SponsorAmbrx, Inc. Industry-sponsored
Drugs / interventionschemotherapy
Locations64 sites (Los Angeles, California and 63 other locations)
Trial IDNCT04829604 on ClinicalTrials.gov

What this trial studies

This is a global, single-arm Phase 2 study evaluating the efficacy of ARX788 in patients with HER2-positive metastatic breast cancer who have previously been treated with T-DXd. Participants will receive ARX788 via intravenous infusion every three weeks. The study aims to assess the treatment's effectiveness and safety in this specific patient population. Eligible patients must have measurable lesions and meet specific criteria regarding prior treatments and organ function.

Who should consider this trial

Good fit: Ideal candidates are adults aged 18 and older with unresectable or metastatic HER2-positive breast cancer who have previously received T-DXd.

Not a fit: Patients who have not been treated with T-DXd or those with early-stage breast cancer may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could provide a new therapeutic option for patients with HER2-positive metastatic breast cancer who have limited treatment alternatives.

How similar studies have performed: Other studies have shown promising results with similar HER2-targeted therapies, indicating potential for success with this approach.

Eligibility criteria

Show full inclusion / exclusion criteria 
Key Inclusion Criteria:

* Age ≥ 18 years and older
* Life expectancy ≥ 6 months
* Unresectable or metastatic breast cancer subjects
* Presence of at least one measurable lesion per RECIST v 1.1
* Subjects must have HER2 positive breast cancer per ASCO-CAP guidelines, documented in a CLIA lab pathology report
* Subjects must have had prior treatment with no more than 5 prior regimens of systemic treatment HER-2 targeting therapy or chemotherapy in the metastatic setting. One of these prior treatments must have been treatment with T-DXd.
* Subjects with stable brain metastases
* Acute toxicities from any prior therapy, surgery, or radiotherapy must have resolved to Grade ≤1 as per the NCI-CTCAE v 5.0, except alopecia, vitiligo, Grade 2 peripheral neuropathy, or endocrine toxicities that are stable on hormone replacement.
* Adequate organ functions
* Willing and able to understand and sign an informed consent inform and to comply with all aspects of the protocol

Key Exclusion Criteria:

Any subject who meets any of the following criteria is excluded from the study:

* History of allergic reactions to any component of ARX788.
* Prior history of interstitial lung disease, pneumonitis, or other clinically significant lung disease. Any requirement for supplemental oxygen.
* Any active ocular infections or chronic corneal disorders
* History of congestive heart failure, unstable angina pectoris, unstable atrial fibrillation, cardiac arrhythmia, or myocardial infarction within 6 months prior to enrollment
* Grade 3 to 4 peripheral neuropathy (NCI CTCAE v 5.0).
* History of unstable central nervous system (CNS) metastases
* Radiotherapy outside of the brain administered \< 7 days prior to first dose of ARX788
* Current severe, uncontrolled systemic disease (eg, clinically significant cardiovascular, pulmonary, or metabolic diseases)
* Any uncontrollable intercurrent illness, infection (including subjects with active, symptomatic Covid-19 infections), or other conditions that could limit study compliance or interfere with assessments
* Exposure to any other investigational or commercial anticancer agents or therapies administered with the intention to treat malignancy within 14 days before the first dose of ARX788

Where this trial is running

Los Angeles, California and 63 other locations

+14 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions HER2 Positive Metastatic Breast CancerHER2-postiveBreast cancerAntibody drugMetastaticARX788HER2
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.