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RGT-419B for HR-Positive, HER2-Negative Advanced Breast Cancer

This study is testing a new drug, RGT-419B, for people with hormone receptor-positive (HR+), HER2-negative advanced or metastatic breast cancer. This is a "first-in-human" study, meaning it's the first time RGT-419B is being given to people. You might receive RGT-419B alone or in combination with hormonal therapy. The main goal is to see how safe RGT-419B is and what side effects it might cause, especially in the first four weeks. To join, you must be at least 18 years old, have advanced breast cancer that has grown after previous treatment with a CDK4/6 inhibitor and hormonal therapy, and have measurable tumors. The study plans to enroll about 64 participants.

Study design
This is a Phase 1, open-label study, meaning both you and your doctors will know which treatment you are receiving. It aims to enroll about 64 participants.
What's involved
Not specified in the trial record.
Compensation
Not stated in the trial record.
Follow-up
Safety and tolerability will be measured at 4 weeks (1 cycle).

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

NCT05304962

FIH Study of RGT-419B Alone and With Endocrine Therapy in HR-Positive, HER2-Negative Advanced/Metastatic Breast Cancer

Recruiting
PHASE1Ages 18+InterventionalTreatment
Regor Pharmaceuticals Inc.
~64 participants
Updated 2026-08-12 on ClinicalTrials.gov
What's tested:RGT-419BRGT-419B in combination with hormonal therapy

At a glance

Recruiting sites
7 of 8 listed sites are recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Safety & Tolerability - Number of subjects with Dose-Limiting Toxicities (DLTs) at each cohort dose level in singlet and doublet therapy
Measured over 4 weeks (1 cycle)

Conditions

Breast Cancer

Explore related trials

Breast Carcinoma

Where it's being run

8 sites across 6 states
California2
Florida2
Georgia1
Massachusetts1
Missouri1
New York1

Who to contact

Joanna Dojillo, MSc
[email protected]
617-315-9070
Email the study team

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Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

Progression after receiving 1 line of prior cyclin-dependent kinase 4 and 6 inhibitor (CDK4/6i) therapy combined with HT in the MBC setting (up to 1 additional line of CDK4/6i is permitted in the post-surgical adjuvant setting);
Subjects must have received therapy for ≥3 months in the MBC setting, or for ≥6 months in the adjuvant setting, prior to progression
Progression after ≤3 lines of prior HT therapy (regardless of whether it is HT alone or in combination with other therapies)
Prior HT combination agents, including SERD, SERM or AI, must have received formal approval by regulatory agency.
≤ 1 prior line of chemotherapy in the metastatic setting 6. Adequate organ function 7. Ability to understand and the willingness to sign a written informed consent document

What this trial measures

  • Safety & Tolerability - Number of subjects with Dose-Limiting Toxicities (DLTs) at each cohort dose level in singlet and doublet therapy4 weeks (1 cycle)

    Number of subjects who have a confirmed DLT at each cohort dose level in singlet and doublet study arms during the first 28-day cycle of RGT-419B treatment.