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HER2 Positive Metastatic Breast CancerPhase 2NCT04829604

ARX788 in HER2-positive, Metastatic Breast Cancer Subjects (ACE-Breast-03)

A Phase 2 study testing ARX788 in people with HER2 Positive Metastatic Breast Cancer, run by Ambrx, Inc. at 33 sites in 3 countries.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
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Trial summary

A Global, Phase 2 Study of ARX788 in HER2-positive Metastatic Breast Cancer Patients who were previously treated with T-DXd Read more about this study

Who is it for?
Ages 18 years and older
Conditions the study is for
HER2 Positive Metastatic Breast Cancer
What is being tested?
ARX788
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
72 participants
Where
33 sitesin 3 countries
Study dates
26 Oct 2021to Jun 2027
Phase
Phase 2
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • 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.
Show all 10Show fewer
  • 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

Who cannot join

  • 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).
Show all 11Show fewer
  • 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

Trial locations and contacts

33 sites in 3 countries.

33 sites in 3 countries

United States25 sites

  • Research Site

    Atlanta, Georgia, 30322

  • Research Site

    Boston, Massachusetts, 02215

  • Research Site

    Camden, New Jersey, 08103

  • Research Site

    Chicago, Illinois, 60611

  • Research Site

    Dallas, Texas, 75246

  • Research Site

    Houston, Texas, 77030

  • Research Site

    Las Vegas, Nevada, 89128

  • Research Site

    Los Angeles, California, 90033

  • Research Site

    Louisville, Kentucky, 40207

  • Research Site

    New Hyde Park, New York, 11042

  • Research Site

    New York, New York, 10028

  • Research Site

    Newport Beach, California, 92663

  • Research Site

    Norfolk, Virginia, 23502

  • Research Site

    Omaha, Nebraska, 68130

  • Research Site

    Philadelphia, Pennsylvania, 19104

  • Research Site

    Portland, Oregon, 97213

  • Research Site

    San Antonio, Texas, 78229

  • Research Site

    San Francisco, California, 94158

  • Research Site

    Shirley, New York, 11967

  • Research Site

    Silver Spring, Maryland, 20904

  • Research Site

    St Louis, Missouri, 63110

  • Research Site

    Tacoma, Washington, 98405

  • Research Site

    The Bronx, New York, 10469

  • Research Site

    Tigard, Oregon, 97223

  • Research Site

    Whittier, California, 90602

Other trials in United States

South Korea5 sites

  • Research Site

    Daegu, 42601

  • Research Site

    Seongnam-si, 13620

  • Research Site

    Seoul, 02841

  • Research Site

    Seoul, 03722

  • Research Site

    Seoul, 05505

Other trials in South Korea

Australia3 sites

  • Research Site

    Frankston, Victoria, 3199

  • Research Site

    Geelong, Victoria, 3220

  • Research Site

    Nedlands, Western Australia, 6009

Other trials in Australia

About this study

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

A Global, Phase 2 Study of ARX788 in HER2-positive Metastatic Breast Cancer Patients who were previously treated with T-DXd

Read the detailed description

A Global, Single Arm, Phase 2 Study of ARX788 in HER2-positive Metastatic Breast Cancer Patients who were previously treated with T-DXd. The ARX788 will be administered every 3 weeks (Q3W) intravenous (IV) infusion.

Being tested
ARX788
Keywords
HER2-postive, Breast cancer, Antibody drug, Metastatic, ARX788, HER2
Medical subject headings
Breast Neoplasms, Neoplasm Metastasis

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • ARX788Drug

    Also called antibody drug conjugate (ADC)

    The active pharmaceutical ingredient in ARX788 is an antibody drug conjugate (ADC) consisting of a humanized anti-HER2 monoclonal antibody (mAb) (IgG1κ) covalently conjugated to two microtubule-disrupting payloads AS269

Study groups in NCT04829604
Study groupRoleWhat they receive
ARX788ExperimentalThe investigational medicinal product (IMP), ARX788, will be administered every 3 weeks (Q3W) by intravenous (IV) infusion.
Receives: Drug: ARX788

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Objective response rate (ORR)

    To evaluate the confirmed objective response rate (ORR) as determined by Investigator assessment based on Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) following treatment with ARX788.

    The ORR is defined as the number of subjects with a BOR of CR or PR divided by the number of response evaluable subjects.

    Measured: 2 years

Secondary outcomes (10)

  1. Duration of response (DOR)

    DOR is defined as the time between the date of first response and the date of disease progression or death, whichever occurs first, will be computed for subjects with a BOR of CR or PR.

    Measured: 2 years

  2. Best overall response (BOR)

    BOR is defined as the best response recorded from the start of the treatment until disease progression/recurrence (taking as reference for progressive disease the smallest measurements recorded since the treatment started)

    Measured: 2 years

  3. Disease control rate (DCR)

    DCR is defined as the proportion of complete response (CR), partial response (PR), and stable disease (SD) rates.

    Measured: 2 years

  4. Overall survival (OS)

    Overall survival (OS) is defined as the time from first dose of study therapy to the date of death (any cause). Subjects who are alive will be censored at the last known time that the subject was alive.

    Measured: 2.5 years

  5. Progression-free survival (PFS)

    PFS is defined as the time between date of first dose of study therapy and date of progression or death, whichever occurs first, will be computed for response evaluable subjects. Subjects will be censored at time of subsequent therapy

    Measured: 2 years

  6. The number of subjects experiencing adverse event TEAEs

    Patient safety and adverse events (AEs) will be evaluated using the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) v.5.0. All AEs and serious adverse events (SAEs) will be assessed to determine the safety and tolerability of the treatment.

    Measured: 2 years

  7. Maximum serum concentration (Cmax) for ARX788

    Pharmacokinetic parameter maximum serum concentration (Cmax) for ARX788, ADC, ADA, total antibody, and pAF-AS269

    Measured: Cycle 1 and cycle 3

  8. Trough concentration (Ctrough) for ARX788

    Pharmacokinetic parameter trough concentration (Ctrough) for ARX788, ADC, total antibody, and pAF-AS269

    Measured: Cycle 1 and cycle 3

  9. Area under the serum concentration-time curve (AUC) for ARX788

    Pharmacokinetic parameter area under the serum concentration-time curve (AUC) for ARX788, ADC, total antibody, and pAF-AS269

    Measured: Cycle 1 and cycle 3

  10. Time to response (TTR)

    Time it takes for patient to respond to study treatment

    Measured: Start of treatment to first objective confirmed BOR of CR or PR, assessed for approximately 2 years

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted2 Apr 2021
  2. Study start26 Oct 2021
  3. Primary completionDec 2026 (estimated)
  4. Study completionJun 2027 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Model description
One single arm, open label with intravenous infusion of ARX788 to assess the anticancer activity and safety of ARX788 in subjects with unresectable or metastatic human epidermal growth factor receptor 2 (HER2)-positive (HER2+) breast cancer.
Masking
None (open label)
Enrolment
72 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT04829604
Sponsor's protocol ID
ACE-Breast-03
Status last verified
Mar 2026
First submitted
18 Mar 2021
Last updated
9 Mar 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing ARX788 in people with HER2 Positive Metastatic Breast Cancer, run by Ambrx, Inc. at 33 sites in 3 countries.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 10 inclusion and 11 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 9 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 33 sites in United States, South Korea, Australia. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Objective response rate (ORR) (time frame: 2 years). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04829604.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 9 Mar 2026.

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