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

June 10, 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

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
155

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • 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 Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

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
        • 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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

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

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: PLX-61639
Drug: PLX-61639
Orally available degrader of SMARCA2

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
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

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
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

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Plexium, Inc.

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • 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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 1, 2025

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 1, 2029

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
September 1, 2030

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
November 20, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
December 2, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
December 16, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
June 12, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 10, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
June 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant 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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