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Study of BTX-9341 for Advanced Breast Cancer

This study is testing a new drug called BTX-9341, either alone or with fulvestrant (a common breast cancer medication), for people with advanced or metastatic (spread to other parts of the body) breast cancer that is hormone receptor positive (HR+) and HER2 negative (HER2-). The main goals are to see if BTX-9341 is safe and well-tolerated, how it moves through the body, and if it shows early signs of working. The study will first find the best dose of BTX-9341, then test that dose with fulvestrant. You may be able to join if you have HR+/HER2- breast cancer that has spread or is locally advanced, and you are at least 18 years old. The study aims to enroll 82 participants.

Study design
This is a Phase 1, multi-center, non-randomized, open-label study. It will involve a dose escalation part to find the right dose, followed by a dose expansion part, and plans to enroll 82 participants.
What's involved
Participants will take BTX-9341 daily by mouth in 28-day cycles. If applicable, fulvestrant will be given as intramuscular injections on Day 15 and then every 28 days.
Compensation
Not stated in the trial record.
Follow-up
Safety and tolerability will be measured for up to 28 days after your last dose of BTX-9341. The study aims to determine the maximum tolerated dose within approximately 1 year from the start.

AI-generated from the public study record. Only the study team can confirm whether you're eligible — confirm details with them before making decisions.

NCT06515470

Safety, Tolerability, Pharmacokinetics, and Preliminary Efficacy of BTX-9341 in Advanced and/or Metastatic Breast Cancer

Recruiting
PHASE1Ages 18+InterventionalTreatment
Biotheryx, Inc.
~82 participants
Updated 2025-06-06 on ClinicalTrials.gov
What's tested:BTX-9341Fulvestrant

At a glance

Recruiting sites
6 of 6 listed sites are recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Safety and Tolerability of BTX-9341
Measured over Up to 28 days after last dose of BTX-9341
+4 more outcomes measured

Conditions

Breast Cancer

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Where it's being run

6 sites across 5 states
Texas2
Minnesota1
Nebraska1
Utah1
Virginia1

Study leadership

  • Jeremy Barton, MD · STUDY_DIRECTOR · Chief Medical Officer

Who to contact

Danette Powell
[email protected]
858-354-1814
Email the study team

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Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

Metastatic and/or locally advanced HR+/HER2- breast cancer (dose escalation: measurable disease and/or at least 1 lytic or mixed \[lytic + sclerotic\] bone lesion that can be assessed by CT or MRI or non-measurable disease \[including bone lesions\]; dose expansion: measurable disease)
Dose escalation: (a) received not more than 1 chemotherapy in the metastatic/advanced setting; (b) no limit to the lines of endocrine therapy (monotherapy or combination therapy) in the metastatic setting; (c) received CDK4/6 inhibitor therapy
Dose expansion: (a) received not more than 1 chemotherapy in metastatic/advanced setting; (b) received not more than 2 lines of endocrine therapy (monotherapy or combination therapy) and must have been on prior endocrine therapy for at least 6 months before progression; (c) received at most 2 lines of CDK4/6 inhibitor therapy (1 in the adjuvant setting and 1 in the metastatic setting) and must have been on prior CDK4/6 inhibitor therapy for at least 6 months
Acceptable hematologic function
Acceptable liver function
Able and willing to sign informed consent
Meets all study requirements in the opinion of the Investigator

Exclusion

RB1 (retinoblastoma) gene mutation
Symptomatic visceral disease
Clinical evidence or history of central nervous system metastasis
Abnormalities in coagulation, such as bleeding diathesis, or treatment with anticoagulants precluding injections of fulvestrant or luteinizing hormone-releasing hormone (LHRH) agonist

What this trial measures

  • Safety and Tolerability of BTX-9341Up to 28 days after last dose of BTX-9341

    Frequency and severity, incidence of treatment-emergent and treatment-related adverse events using NCI-CTCAE v5.0

  • Part A: Number of Participants With Dose Limiting Toxicities (DLTs)28 days

    DLT rate in Cycle 1

  • Part A: Determine MTD/MED of BTX-9341 in monotherapyApproximately 1 year from study start

    Based on CTCAE v5.0 assessment of adverse events

  • Part A: Determine MTD/MED of BTX-9341 in combination therapyApproximately 18 months from study start

    Based on CTCAE v5.0 assessment of adverse events

  • Part B Combination Therapy: Objective Response (OR) rateApproximately 18 months from start of Part B

    OR is the confirmed complete response (CR) or partial response (PR) according to Response Evaluation Criteria in Solid Tumor (RECIST) version 1.1 as determined by Investigator assessment