Phase 1, Safety and Tolerability Study of XmAb541 and XmAb808 in Advanced Solid Tumors

August 11, 2026 updated by: Xencor, Inc.

A Phase 1 Trial, Evaluating the Safety and Tolerability of XmAb541 in Combination With XmAb808 in Advanced Solid Tumors

The primary purpose of this study is to determine whether the combination of the investigational drug XmAb541 in combination with the investigational drug XmAb808 is safe and well tolerated, and to determine an optimal and safe dose(s) for further study. The study will also evaluate the effect of XmAb541 in combination with XmAb808 on participants' tumor outcomes.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

90

Phase

  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • New York
      • Lake Success, New York, United States, 11042
        • Recruiting
        • Xencor Investigative Site
      • New York, New York, United States, 10029
        • Recruiting
        • Xencor Investigative Site
      • The Bronx, New York, United States, 10461
        • Recruiting
        • Xencor Investigative Site
    • Texas
      • Fort Worth, Texas, United States, 76104
        • Recruiting
        • Xencor Investigative Site

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age ≥ 18 years.
  • CLDN6+ tumor
  • Histological or cytological documentation of locally advanced, recurrent, or metastatic high grade serous ovarian carcinoma (HGSOC) including fallopian tube or primary peritoneal origin
  • Adequate Eastern Cooperative Oncology Group performance status
  • Life expectancy ≥ 3 months
  • Adequate organ function

Exclusion Criteria:

  • Prior exposure to a CLDN6 targeting immune cell engager
  • Patients with treated brain metastases may participate, provided they are radiologically stable.
  • Active known or suspected autoimmune disease
  • Have any condition requiring systemic treatment with corticosteroids, prednisone equivalents, or other immunosuppressive medications within 14 days prior to first dose of study drug
  • Clinically significant cardiovascular, pulmonary or gastrointestinal disease
  • Active viral hepatitis B or hepatitis C

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Sequential Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Dose Escalation and Dose Expansion of XmAb541 and XmAb808
Biological: XmAb541
Monoclonal Bispecific Antibody
Biological: XmAb808
Monoclonal Bispecific Antibody

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Incidence of Adverse Events
Time Frame: Day 1 to 2 years
Day 1 to 2 years
Incidence of dose-limiting toxicities
Time Frame: Day 1 to Day 43
Day 1 to Day 43

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Measurement of Ctrough
Time Frame: Day 1 to 2 years
Plasma concentration before next dose
Day 1 to 2 years
Objective Response Rate
Time Frame: Day 1 to 2 years
Objective Response Rate by RECIST 1.1 assessment of CT/MRI imaging
Day 1 to 2 years
Measurement of Cmax
Time Frame: Day 1 - 2 years
Peak Plasma Concentration
Day 1 - 2 years
Measurement of area under curve (AUC)
Time Frame: Day 1 to 2 years
Area under the plasma concentration versus time curve
Day 1 to 2 years
Duration of Response
Time Frame: Day 1 to 2 years
Duration of Objective Response Rate by RECIST 1.1 assessment of CT/MRI imaging
Day 1 to 2 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Xencor, Inc.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 30, 2026

Primary Completion (Estimated)

December 1, 2028

Study Completion (Estimated)

December 1, 2028

Study Registration Dates

First Submitted

May 11, 2026

First Submitted That Met QC Criteria

May 11, 2026

First Posted (Actual)

May 18, 2026

Study Record Updates

Last Update Posted (Actual)

August 13, 2026

Last Update Submitted That Met QC Criteria

August 11, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • XmAb541-02

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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