HER2-positive Breast CancerPhase 1NCT05514717
A Study of XMT-2056 in Advanced/Recurrent Solid Tumors That Express HER2
A Phase 1 study testing XMT-2056 in people with HER2-positive Breast Cancer and HER2-positive Gastric Cancer, run by Day One Biopharmaceuticals, Inc. at 14 sites in United States.
Trial summary
A Study of XMT-2056 in advanced/recurrent solid tumors that express HER2. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- HER2-positive Breast Cancer, HER2-positive Gastric Cancer, HER2-positive Non-Small Cell Lung Cancer
- What is being tested?
- XMT-2056
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 57 participants
- Where
- 14 sitesUnited States
- Study dates
- 24 Jan 2023to 22 May 2026
- Phase
- Phase 1
- Are there results?
- None posted in the registry
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
- Participant has recurrent or metastatic solid tumors with HER2 expression and has disease progression after treatment, is intolerant to treatment, or is contraindicated with available anti-cancer therapies known to confer benefit, based on investigator's judgement. Note: Participants must have HER2 positivity per the results of their most recent tumor tissue testing, defined as IHC 3+ or IHC 2+ in combination with in situ hybridization (ISH)+. Participants with ERBB2-activating mutations or ERBB2 gene amplification in the absence of HER2 positivity are considered ineligible.
- Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.
- Participant must have measurable disease as defined by RECIST version 1.1.
- Participant has fresh tumor biopsy tissue available for submission to central laboratory. If obtaining fresh tumor tissue is medically contraindicated, archival tumor tissue can be submitted following written approval of the request by the study Medical Monitor. Samples must be obtained after the participant's most recent HER2-targeting therapy unless determined to be medically contraindicated after discussion with the medical monitor.
Who cannot join
- • Participant is receiving immunosuppressive doses of systemic medications, (doses >10 mg/day prednisone or equivalent) that cannot be discontinued for at least 2 weeks before the first dose and during study drug treatment administration. Note: physiologic hormone replacement therapy is an exception.
- Participant has received prior treatment targeting STING pathway.
- Diagnosis of additional malignancy that required active treatment (including surgery, systemic therapy, and radiation) within the last 2 years, expect for adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the breast or the cervix. Participants with an additional malignancy that has a low risk for recurrence may be eligible after discussion with the study Medical Monitor.
- Participants have untreated CNS metastases (including new and progressive brain metastases), history of leptomeningeal metastasis, or carcinomatous meningitis.
- Participants are eligible if CNS metastases are adequately treated and participants are neurologically stable for at least 2 weeks prior to enrollment.
- In addition, participants must be either off corticosteroids, or on a stable/decreasing dose of ≤ 10 mg prednisone daily (or equivalent).
Trial locations and contacts
14 sites in 1 country.
14 sites in 1 country
United States14 sites
Emory Healthcare, Emory Clinic
Atlanta, Georgia, 30322
Massachusetts General Hospital
Boston, Massachusetts, 02114
AdventHealth Celebration
Celebration, Florida, 34747
The Ohio State University Comprehensive Cancer Center
Columbus, Ohio, 43212
Karmanos Cancer Institute
Detroit, Michigan, 48201
Hackensack University Medical Center
Hackensack, New Jersey, 07601
The University of Texas MD Anderson Cancer Center
Houston, Texas, 77030
University of South California
Los Angeles, California, 90033
University of California Los Angeles
Los Angeles, California, 90095
Tennessee Oncology, PLLC
Nashville, Tennessee, 37203
New York University Medical Oncology Associates
New York, New York, 10016
Icahn School of Medicine at Mount Sinai
New York, New York, 10029
Memorial Sloan Kettering Cancer Center
New York, New York, 10065
Stanford University Medical Center
Stanford, California, 94305
About this study
Official title: A Phase 1, First-in-Human, Dose Escalation and Expansion, Multicenter Study of XMT-2056 in Participants With Advanced/Recurrent Solid Tumors That Express HER2
A Study of XMT-2056 in advanced/recurrent solid tumors that express HER2.
Read the detailed description
The first-in-human (FIH) study of XMT-2056 is a Phase 1, open-label study of XMT-2056 in previously treated patients with advanced/recurrent solid tumors expressing HER2. The XMT-2056 monotherapy trial will consist of dose escalation (DES) and expansion (EXP) parts.
DES will be the dose-finding portion of the study to assess the safety and tolerability of XMT-2056 and determine the maximum tolerated dose (MTD) and/or Recommended Phase 2 Dose (RP2D). The RP2D will be determined based on the totality of the clinical data, including safety and preliminary anti-tumor effect, PK, and relevant biomarker data.
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
XMT-2056Drug
XMT-2056 will be administered through a vein in your arm or port catheter (intravenously)
| Study group | Role | What they receive |
|---|---|---|
| XMT-2056 | Experimental | XMT-2056 alone (monotherapy) Receives: Drug: XMT-2056 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Frequency of dose-limiting toxicities (DLTs) associated with XMT-2056 during the first cycle of treatment (Dose Escalation)
Determine the maximum tolerated dose (MTD) of XMT-2056
Measured: 15 months
Incidence of adverse events (Dose Escalation and Dose Expansion)
Assess the safety and tolerability of XMT-2056 by determining the number of patients with adverse events from date of first dose to 30 days post last dose.
Measured: 3 years
Objective Response Rate (ORR) (Dose Expansion)
The percentage of patients with a best overall response of confirmed complete or partial response as assessed by the investigator per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1
Measured: 3 years
Secondary outcomes (11)
Objective Response Rate (ORR) (Dose Escalation)
The percentage of patients with a best overall response of confirmed complete or partial response as assessed by the investigator per Resist Evaluation Criteria in Solid Tumors (RECIST) version 1.1
Measured: 3 years
Duration of response (DOR) (Dose Escalation and Dose Expansion)
The time from when response criteria are first met until disease progression or death in participants who achieve a confirmed complete or partial response.
Measured: 3 years
Disease control rate (DCR) (Dose Escalation and Dose Expansion)
The percentage of patients who achieve a complete response, partial response or stable disease as the result of study treatment
Measured: 3 years
Time of maximum observed plasma concentration of XMT-2056 (Tmax) (Dose Escalation and Dose Expansion)
Assess the pharmacokinetics of XMT-2056
Measured: 3 years
Maximum observed plasma concentration of XMT-2056 (Cmax) (Dose Escalation and Dose Expansion)
Assess the pharmacokinetics of XMT-2056
Measured: 3 years
Area under the concentration-time curve of XMT-2056 (AUC) (Dose Escalation and Dose Expansion)
Assess the pharmacokinetics of XMT-2056
Measured: 3 years
Systemic clearance of XMT-2056 (Dose Escalation and Dose Expansion)
Assess the pharmacokinetics of XmT-2056 by measuring the rate at which the drug is eliminated from the body
Measured: 3 years
Apparent terminal elimination of half-life of XMT-2056 (Dose Escalation and Dose Expansion)
Assess the pharmacokinetics of XMT-2056
Measured: 3 years
Volume of Distribution (Dose Escalation and Dose Expansion)
Assess the pharmacokinetics of XMT-2056
Measured: 3 years
Trough concentration of XMT-2056 (Ctrough) (Dose Escalation and Dose Expansion)
Assess the pharmacokinetics of XMT-2056 by measuring the lowest concentration of drug before dosing
Measured: 3 years
Serum samples for analysis of XMT-2056 antidrug and neutralizing antibodies (ADA/nAb) (Dose Escalation and Dose Expansion)
Assess the development of antidrug antibodies (ADA) and neutralizing antibodies (nAB) to XMT-2056
Measured: 3 years
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Aug 2022
- Study start24 Jan 2023
- Primary completion22 May 2026
- Study completion22 May 2026
Why it stopped: Development discontinued.
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HER2-positive Breast CancerStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
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 1
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 57 participants (actual)
Sponsor and investigators
- Lead sponsor
- Day One Biopharmaceuticals, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Brad Sumrow, MD, Study director, Mersana Therapeutics
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05514717
- Sponsor's protocol ID
- MER-XMT-2056-1
- Status last verified
- Jun 2026
- First submitted
- 8 Aug 2022
- Last updated
- 18 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 18 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 1, First-in-Human, Dose Escalation and Expansion, Multicenter Study of XMT-2056 in Participants With Advanced/Recurrent Solid Tumors That Express HER2
- ClinicalTrials.gov ID
- NCT05514717
- Acronym / sponsor ID
- MER-XMT-2056-1
- Conditions
- HER2-positive Breast Cancer, HER2-positive Gastric Cancer, HER2-positive Non-Small Cell Lung Cancer, HER2-positive Colorectal Cancer, HER2-positive Tumors, HER2 Low Breast Cancer
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- TerminatedReason stopped: Development discontinued.
- Enrolment
- 57 participants (actual)
- Lead sponsor
- Day One Biopharmaceuticals, Inc.Industry (pharma, biotech, devices)
- Study start
- 24 Jan 2023 (actual)
- Primary completion
- 22 May 2026 (actual)
- Study completion
- 22 May 2026 (actual)
- First posted
- 24 Aug 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
A Study of XMT-2056 in advanced/recurrent solid tumors that express HER2.
Detailed description
The first-in-human (FIH) study of XMT-2056 is a Phase 1, open-label study of XMT-2056 in previously treated patients with advanced/recurrent solid tumors expressing HER2. The XMT-2056 monotherapy trial will consist of dose escalation (DES) and expansion (EXP) parts.
DES will be the dose-finding portion of the study to assess the safety and tolerability of XMT-2056 and determine the maximum tolerated dose (MTD) and/or Recommended Phase 2 Dose (RP2D). The RP2D will be determined based on the totality of the clinical data, including safety and preliminary anti-tumor effect, PK, and relevant biomarker data.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| XMT-2056 | Experimental | Drug: XMT-2056XMT-2056 alone (monotherapy) |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- Participant has recurrent or metastatic solid tumors with HER2 expression and has disease progression after treatment, is intolerant to treatment, or is contraindicated with available anti-cancer therapies known to confer benefit, based on investigator's judgement. Note: Participants must have HER2 positivity per the results of their most recent tumor tissue testing, defined as IHC 3+ or IHC 2+ in combination with in situ hybridization (ISH)+. Participants with ERBB2-activating mutations or ERBB2 gene amplification in the absence of HER2 positivity are considered ineligible.
- Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.
- Participant must have measurable disease as defined by RECIST version 1.1.
- Participant has fresh tumor biopsy tissue available for submission to central laboratory. If obtaining fresh tumor tissue is medically contraindicated, archival tumor tissue can be submitted following written approval of the request by the study Medical Monitor. Samples must be obtained after the participant's most recent HER2-targeting therapy unless determined to be medically contraindicated after discussion with the medical monitor.
Key exclusion criteria (6 listed)
- • Participant is receiving immunosuppressive doses of systemic medications, (doses >10 mg/day prednisone or equivalent) that cannot be discontinued for at least 2 weeks before the first dose and during study drug treatment administration. Note: physiologic hormone replacement therapy is an exception.
- Participant has received prior treatment targeting STING pathway.
- Diagnosis of additional malignancy that required active treatment (including surgery, systemic therapy, and radiation) within the last 2 years, expect for adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the breast or the cervix. Participants with an additional malignancy that has a low risk for recurrence may be eligible after discussion with the study Medical Monitor.
- Participants have untreated CNS metastases (including new and progressive brain metastases), history of leptomeningeal metastasis, or carcinomatous meningitis.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| XMT-2056XMT-2056 will be administered through a vein in your arm or port catheter (intravenously) | Drug | XMT-2056 |
Primary outcome
Frequency of dose-limiting toxicities (DLTs) associated with XMT-2056 during the first cycle of treatment (Dose Escalation)
Time frame: 15 months
Determine the maximum tolerated dose (MTD) of XMT-2056
Incidence of adverse events (Dose Escalation and Dose Expansion)
Time frame: 3 years
Assess the safety and tolerability of XMT-2056 by determining the number of patients with adverse events from date of first dose to 30 days post last dose.
Objective Response Rate (ORR) (Dose Expansion)
Time frame: 3 years
The percentage of patients with a best overall response of confirmed complete or partial response as assessed by the investigator per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1
11 secondary outcomes
Objective Response Rate (ORR) (Dose Escalation)
Time frame: 3 years
Duration of response (DOR) (Dose Escalation and Dose Expansion)
Time frame: 3 years
Disease control rate (DCR) (Dose Escalation and Dose Expansion)
Time frame: 3 years
Time of maximum observed plasma concentration of XMT-2056 (Tmax) (Dose Escalation and Dose Expansion)
Time frame: 3 years
Maximum observed plasma concentration of XMT-2056 (Cmax) (Dose Escalation and Dose Expansion)
Time frame: 3 years
Area under the concentration-time curve of XMT-2056 (AUC) (Dose Escalation and Dose Expansion)
Time frame: 3 years
Systemic clearance of XMT-2056 (Dose Escalation and Dose Expansion)
Time frame: 3 years
Apparent terminal elimination of half-life of XMT-2056 (Dose Escalation and Dose Expansion)
Time frame: 3 years
Volume of Distribution (Dose Escalation and Dose Expansion)
Time frame: 3 years
Trough concentration of XMT-2056 (Ctrough) (Dose Escalation and Dose Expansion)
Time frame: 3 years
Serum samples for analysis of XMT-2056 antidrug and neutralizing antibodies (ADA/nAb) (Dose Escalation and Dose Expansion)
Time frame: 3 years
Results and safety
The study was stopped early (reason given: Development discontinued.). Results are not available in the source record.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 18 Jun 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Brad Sumrow, MD study director
Mersana Therapeutics
14 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing XMT-2056 in people with HER2-positive Breast Cancer and HER2-positive Gastric Cancer, run by Day One Biopharmaceuticals, Inc. at 14 sites in United States.
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 4 inclusion and 6 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: stopped early, as of the sponsor's last update on 18 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 14 sites in United States. 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 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study was stopped early (reason given: Development discontinued.). Results are not available in the source record.
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?
Frequency of dose-limiting toxicities (DLTs) associated with XMT-2056 during the first cycle of treatment (Dose Escalation) (time frame: 15 months). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 18 Jun 2026.