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Breast CancerPhase 1NCT06515470

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

A Phase 1 study testing BTX-9341 and Fulvestrant in people with Breast Cancer, run by Biotheryx, Inc. at 6 sites in United States.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

The purpose of this study is to test BTX-9341 alone or in combination with fulvestrant (a currently marketed medication for breast cancer) in participants with advanced and/or metastatic hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) breast cancer. Read more about this study

Who is it for?
Ages 18 years and older
Conditions the study is for
Breast Cancer
What is being tested?
BTX-9341 and Fulvestrant
Could I receive a placebo?
No, everyone receives an active treatment
How many people
82 participants
Where
6 sitesUnited States
Study dates
3 Jul 2024to 31 Dec 2027
Phase
Phase 1
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • 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
  • ANC ≥ 1500 per mL. Note: Use of growth-factors to maintain the ANC criterion is prohibited.
  • Platelet count ≥ 100,000 per mL. Note: Use of transfusions or thrombopoietic agents to achieve the baseline platelet count criterion is prohibited.
Show all 13Show fewer
  • Hemoglobin ≥ 9.0 g/dL. Note: Packed red blood cell transfusion is allowed up to 14 days prior to trial entry.
  • Acceptable liver function
  • Bilirubin ≤ 2.0 × institutional upper limit of normal (ULN) (or < 3.0 × institutional ULN if Gilbert's disease is present)
  • Alanine transaminase (ALT)/aspartate aminotransferase (AST) ≤ 3.0 × institutional ULN (≤ 5.0 × institutional ULN if liver metastases present)
  • Alkaline phosphatase ≤ 2.5 × institutional ULN (≤ 5.0 × institutional ULN if bone or liver metastases present)
  • Able and willing to sign informed consent
  • Meets all study requirements in the opinion of the Investigator

Who cannot join

  • 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

Trial locations and contacts

6 sites in 1 country. Contact the study team or a site near you to ask about taking part.

Danette Powell contact

858-354-1814

c-dpowell@biotheryx.com

6 sites in 1 country

United States6 sites, 6 recruiting

  • Biotheryx Investigative Site

    Fairfax, Virginia, 22031

    Biotheryx Investigative Site

    Recruiting

  • Biotheryx Investigative Site

    Houston, Texas, 77030

    Biotheryx Investigative Site

    Recruiting

  • Biotheryx Investigative Site

    Omaha, Nebraska, 68130

    Biotheryx Investigative Site

    Recruiting

  • Biotheryx Investigative Site

    Rochester, Minnesota, 55905

    Biotheryx Investigative Site

    Recruiting

  • Biotheryx Investigative Site

    San Antonio, Texas, 78229

    Biotheryx Investigative Site

    Recruiting

  • Biotheryx Investigative Site

    West Valley City, Utah, 84119

    Biotheryx Investigative Site

    Recruiting

Other trials in United States

About this study

Official title: A First-in-Human, Open-Label, Dose Escalation and Expansion Trial of BTX-9341 in Participants With Advanced and/or Metastatic Breast Cancer

The purpose of this study is to test BTX-9341 alone or in combination with fulvestrant (a currently marketed medication for breast cancer) in participants with advanced and/or metastatic hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) breast cancer. The study includes a dose escalation part (Part A) where small groups of participants will receive increasing doses of BTX-9341 or BTX-9341 + fulvestrant followed by a dose expansion part (Part B) where participants will receive the dose of BTX-9341 selected in Part A + fulvestrant.

Read the detailed description

This first-in-human (FIH), Phase 1 study of BTX-9341 is multicenter, nonrandomized, and open-label to evaluate the safety, tolerability, pharmacokinetics (PK), and preliminary efficacy of BTX-9341 in participants with advanced and/or metastatic HR+/HER2 breast cancer. The study will include a dose escalation part (Part A) followed by a dose expansion part (Part B). During Part A, BTX-9341 will initially be dose escalated alone and then in combination with fulvestrant. A single combination therapy cohort of BTX-9341 + fulvestrant will be further explored in Part B. BTX-9341 will be administered orally in 28-day treatment cycles.

Conditions
Breast Cancer
Being tested
BTX-9341, Fulvestrant
Keywords
HR+/HER2-
Medical subject headings
Breast Neoplasms

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • BTX-9341Drug

    Daily oral dose in 28-day cycles until maximum tolerated dose (MTD) or maximum evaluable dose (MED) determined

  • FulvestrantDrug

    Also called Faslodex

    500 mg intramuscular injections on Day 15 and then every 28 days

  • BTX-9341Drug

    Daily oral dose in 28-day cycles using dose determined in Part A

Study groups in NCT06515470
Study groupRoleWhat they receive
BTX-9341 (Part A)ExperimentalBTX-9341 capsule(s) administered orally once daily (QD) in 28-day cycles
Receives: Drug: BTX-9341
BTX-9341 + fulvestrant (Part A)ExperimentalBTX-9341 capsule(s) administered orally QD in 28-day cycles and fulvestrant intermuscular injections on Day 15 and then once every 28 days
Receives: Drug: BTX-9341; Drug: Fulvestrant
BTX-9341 + fulvestrant (Part B)ExperimentalBTX-9341 capsule(s) administered orally QD in 28-day cycles and fulvestrant intermuscular injections on Day 15 and then once every 28 days
Receives: Drug: Fulvestrant; Drug: BTX-9341

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Safety and Tolerability of BTX-9341

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

    Measured: Up to 28 days after last dose of BTX-9341

  2. Part A: Number of Participants With Dose Limiting Toxicities (DLTs)

    DLT rate in Cycle 1

    Measured: 28 days

  3. Part A: Determine MTD/MED of BTX-9341 in monotherapy

    Based on CTCAE v5.0 assessment of adverse events

    Measured: Approximately 1 year from study start

  4. Part A: Determine MTD/MED of BTX-9341 in combination therapy

    Based on CTCAE v5.0 assessment of adverse events

    Measured: Approximately 18 months from study start

  5. Part B Combination Therapy: Objective Response (OR) rate

    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

    Measured: Approximately 18 months from start of Part B

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted23 Jul 2024
  2. Study start3 Jul 2024
  3. Primary completion30 Sep 2027 (estimated)
  4. Study completion31 Dec 2027 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 1
Primary purpose
Treatment
Allocation
Non-randomised
Intervention model
Sequential
Masking
None (open label)
Enrolment
82 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06515470
Sponsor's protocol ID
BTX-9341-101
Status last verified
Jun 2025
First submitted
17 Jul 2024
Last updated
6 Jun 2025
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A Phase 1 study testing BTX-9341 and Fulvestrant in people with Breast Cancer, run by Biotheryx, Inc. at 6 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 13 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 6 Jun 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 6 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Danette Powell (858-354-1814, c-dpowell@biotheryx.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Safety and Tolerability of BTX-9341 (time frame: Up to 28 days after last dose of BTX-9341). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06515470.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 6 Jun 2025.

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