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Testing a new drug called XMT-1660 for solid tumors

A Phase 1, First-in-human, Dose Escalation and Expansion, Multicenter Study of XMT-1660 in Participants With Solid Tumors

Phase 1 Interventional Mersana Therapeutics · NCT05377996

This study is testing a new drug called XMT-1660 to see if it is safe and effective for people with hard-to-treat solid tumors like triple negative breast cancer and ovarian cancer.

Quick facts

PhasePhase 1
Study typeInterventional
Enrollment319 (estimated)
Ages18 Years and up
SexAll
SponsorMersana Therapeutics Industry-sponsored
Drugs / interventionsradiation
Locations26 sites (Phoenix, Arizona and 25 other locations)
Trial IDNCT05377996 on ClinicalTrials.gov

What this trial studies

This first-in-human study evaluates the safety and side effects of XMT-1660 in participants with recurrent or advanced solid tumors, including triple negative breast cancer and ovarian cancer. The trial consists of two parts: a Dose Escalation phase to determine the appropriate dosage and a Dose Expansion phase to assess the drug's safety and efficacy. Participants will undergo tumor tissue testing and may need a biopsy if necessary. The study aims to provide insights into the potential therapeutic benefits of XMT-1660 for patients with difficult-to-treat cancers.

Who should consider this trial

Good fit: Ideal candidates include individuals with recurrent or advanced solid tumors who have an ECOG performance status of 0 or 1.

Not a fit: Patients with non-recurrent solid tumors or those who do not meet the eligibility criteria may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could offer a new treatment option for patients with advanced solid tumors.

How similar studies have performed: Other studies have shown promise with similar investigational drugs, but this specific approach with XMT-1660 is novel.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* Recurrent or advanced solid tumor and has disease
* Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
* Participants in DES must have at least one non-target lesion as defined by RECIST version 1.1. Participants in Backfill Cohorts and EXP must have at least one measurable disease (target) lesion as defined by RECIST version 1.1.
* Tumor tissue, either archival or from a fresh tumor biopsy, available for testing or be willing to undergo a minimally invasive tumor biopsy to obtain tumor tissue for local testing, if not medically contraindicated, prior to Cycle 1 Day 1
* Brain magnetic resonance imaging (MRI) during the Screening period unless obtained within 30 days prior to Screening (based on standard clinical care), if they meet either of the following criteria:

  1. All participants with TNBC
  2. Participants with a history of brain metastases or with neurologic symptoms or signs suspicious for brain metastases.

Exclusion Criteria:

* Prior treatment with an Antibody Drug Conjugate (ADC) containing an auristatin payload. Prior treatment with another ADC containing other payloads is allowed.
* Major surgery within 28 days of starting study treatment, systemic anticancer therapy within the time period of 28 days or 5 half-lives of the prior therapy before starting study treatment (14 days or 5 half-lives for small molecule targeted therapy), whichever is less, or palliative radiation therapy to the chest within 3 months of starting study treatment or to other anatomic sites within 14 days of starting study treatment.
* Diagnosis of additional malignancy that required active treatment (including surgery, systemic therapy, and radiation) within 2 years prior to screening, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ of the breast or of the cervix.
* Untreated CNS metastases (including new and progressive brain metastases), history of leptomeningeal metastasis or carcinomatous meningitis.
* Prior B7-H4 targeted treatment.
* History of cirrhosis, hepatic fibrosis, esophageal or gastric varices, or other clinically significant liver diseases.
* Current severe, uncontrolled systemic disease (e.g. clinically significant cardiovascular, pulmonary, or metabolic disease) or intercurrent illness that could increase the risk of serious adverse events (SAEs) or interfere with per-protocol evaluations, in the judgment of either the Sponsor or the Investigator.
* Clinically significant cardiovascular disease

Where this trial is running

Phoenix, Arizona and 25 other locations

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 Triple Negative Breast CancerBreast CancerEndometrial CancerOvarian CancerFallopian Tube CancerPrimary Peritoneal Cavity CancerAdenoid Cystic Carcinoma
Last reviewed 2026-06-09 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.