First-in-Human Study of PLX-61639 in Locally Advanced or Metastatic Solid Tumors

May 27, 2026 updated by: Plexium, Inc.

A Phase 1, First-in-Human Study of the SMARCA2 Degrader, PLX-61639, in Patients With SMARCA4-Mutated Locally Advanced or Metastatic Solid Tumors

A multicenter, single-arm, first-in-human study to investigate the safety, pharmacokinetics, and preliminary antitumor activity of PLX-61639 in participants with locally advanced or metastatic, relapsed/refractory, SMARCA4-deficient solid tumors who are intolerant of or have failed available, approved therapies.

The study will be conducted in 3 parts: dose escalation (Part 1), dose optimization (Part 2), and cohort expansion (Part 3). Each part of the study will consist of a Screening Phase lasting up to 28 days during which participants will be assessed for eligibility, a Treatment Phase beginning on Cycle 1 Day 1 and consisting of consecutive 28-day cycles, an End of Treatment Visit, and a Post-Treatment Follow-Up Phase.

Participants will receive their assigned dose of PLX-61639 administered orally, once daily until progression/relapse, intolerance, death, or withdrawal from study treatment by the Investigator or participant.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

155

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
    • Arizona
      • Scottsdale, Arizona, United States, 85258
        • Recruiting
        • Research Site
    • California
      • Duarte, California, United States, 91010
        • Recruiting
        • Research Site
      • Orange, California, United States, 92868
        • Recruiting
        • Research Site
    • Massachusetts
      • Boston, Massachusetts, United States, 02114
        • Not yet recruiting
        • Research Site
    • Missouri
      • St Louis, Missouri, United States, 63110
        • Recruiting
        • Research Site
    • New York
      • New York, New York, United States, 10044
        • Recruiting
        • Research Site
    • North Carolina
      • Durham, North Carolina, United States, 27710
        • Recruiting
        • Research Site
    • Ohio
      • Cleveland, Ohio, United States, 44106
        • Recruiting
        • Research Site
    • Texas
      • San Antonio, Texas, United States, 78229
        • Recruiting
        • Research Site
    • Virginia
      • Fairfax, Virginia, United States, 22031
        • Recruiting
        • Research 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

Key Inclusion Criteria:

  • Participants with locally advanced or metastatic, relapsed/refractory, solid tumors harboring a SMARCA4 loss-of-function mutation that have progressed on, are intolerant of, or not otherwise candidates for available approved therapies
  • Adequate liver bone marrow, coagulation, renal, and cardiopulmonary function
  • Measurable disease per RECIST 1.1
  • ECOG PS of 0 or 1

Key Exclusion Criteria:

  • Germline SMARCA4 mutations
  • Known SMARCA2 mutation or loss of expression
  • Symptomatic CNS disease
  • Prior treatment with another SMARCA2-directed therapy
  • History of other malignancies
  • Clinically significant heart disease
  • Uncontrolled hypertension
  • Prolongation of QT interval

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: PLX-61639
Drug: PLX-61639
Orally available degrader of SMARCA2

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Treatment Emergent Adverse Events
Time Frame: From enrollment to 28 days after the last dose of PLX-61639
From enrollment to 28 days after the last dose of PLX-61639
Dose-Limiting Toxicities
Time Frame: From enrollment to 28 days after first dose of PLX-61639
From enrollment to 28 days after first dose of PLX-61639

Secondary Outcome Measures

Outcome Measure
Time Frame
Dose reductions due to Adverse Events
Time Frame: From Day 1 to the end of PLX-61639 treatment, an average of 1 year
From Day 1 to the end of PLX-61639 treatment, an average of 1 year
Study treatment discontinuations for reasons other than disease progression
Time Frame: From Day 1 to the end of PLX-61639 treatment, an average of 1 year
From Day 1 to the end of PLX-61639 treatment, an average of 1 year
Pharmacokinetics of PLX-61639: Cmax
Time Frame: From Day 1 to Day 15 of Cycle 1 (Part 1 only) (each cycle is 28 days)
From Day 1 to Day 15 of Cycle 1 (Part 1 only) (each cycle is 28 days)
Pharmacokinetics of PLX-61639: Tmax
Time Frame: From Day 1 to Day 15 of Cycle 1 (Part 1 only) (each cycle is 28 days)
From Day 1 to Day 15 of Cycle 1 (Part 1 only) (each cycle is 28 days)
Pharmacokinetics of PLX-61639: AUC0-last
Time Frame: From Day 1 to Day 16 of Cycle 1 (Part 1 only) (each cycle is 28 days)
From Day 1 to Day 16 of Cycle 1 (Part 1 only) (each cycle is 28 days)
Radiographic response to PLX-61639
Time Frame: From Day 1 to the end of PLX-61639 treatment, an average of 1 year
From Day 1 to the end of PLX-61639 treatment, an average of 1 year
Time to response (TTR) to PLX-61639
Time Frame: From Day 1 to achievement of partial or complete response, up to 24 weeks
From Day 1 to achievement of partial or complete response, up to 24 weeks
Duration of response (DoR) to PLX-61639
Time Frame: From first documented partial or complete response to disease progression or death, an average of 1 year
From first documented partial or complete response to disease progression or death, an average of 1 year
Progression Free Survival (PFS) of PLX-61639
Time Frame: From Day 1 to disease progression or death, an average of 1 year
From Day 1 to disease progression or death, an average of 1 year

Collaborators and Investigators

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

Sponsor

Plexium, Inc.

Investigators

  • Study Director: Chief Medical Officer, Plexium, 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)

December 1, 2025

Primary Completion (Estimated)

December 1, 2029

Study Completion (Estimated)

September 1, 2030

Study Registration Dates

First Submitted

November 20, 2025

First Submitted That Met QC Criteria

December 2, 2025

First Posted (Actual)

December 16, 2025

Study Record Updates

Last Update Posted (Actual)

May 29, 2026

Last Update Submitted That Met QC Criteria

May 27, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • PLX-61639-101

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

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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