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

RECRUITINGPHASE1

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

First-in-Human, Escalating Oral Dose Study of RGT-419B Given Alone and With Endocrine Therapy in Subjects With Hormone Receptor Positive, Human Epidermal Growth Factor Receptor 2 Negative Advanced/Metastatic Breast Cancer

NCT05304962•Regor Pharmaceuticals Inc.

View on ClinicalTrials.gov

Summary

This is a phase I, First-in-Human (FIH), open-label study to evaluate the safety, tolerability, pharmacokinetic (PK) profile, and preliminary efficacy of RGT-419B administered orally as monotherapy OR in combination with Hormonal Therapy in subjects with HR+, HER2- locally advanced and unresectable (Stage III) or metastatic (Stage IV) breast cancer whose disease has progressed during prior therapy with an approved CDK4/6i plus hormonal therapy.

Eligibility

Age

18 - No limit years

Sex

ALL

Healthy Volunteers

Inclusion Criteria

•1. Male or female \>/= 18 years old
•2. ECOG Performance Status 0 to 1
•3. Subjects must have histologically or cytologically confirmed diagnosis of ER+, HER2- ABC consistent with ASCO CAP guidelines that is locally advanced and unresectable (Stage III) or metastatic (Stage IV) BC.
•4. Measurable AND evaluable lesions at baseline per RECIST v1.1.
•5. Eligible subjects must meet all of the following criteria:
•* 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
+2 more criteria

Exclusion Criteria

•1. Presence of visceral metastases with severe organ dysfunction as evidence by signs and symptoms, laboratory studies, lymphangitic spread and/or rapid progression of disease
•2. Pregnant or planning to become pregnant
•3. Prior irradiation to \>25% of the bone marrow and/or inadequate bone marrow function or evidence of clinically significant end-organ damage
•4. Major surgery, chemotherapy, targeted therapy, experimental agents, or radiation within 14-28 days prior to Cycle 1, Day 1
•5. Active, serious medical condition that is not well controlled with locally approved medications allowed by the protocol
•6. History of allergic reactions attributed to compounds of similar chemical or biologic composition to the drugs used in the study

Locations (8)

University of California, San Diego

La Jolla, California, United States

University California, Los Angeles

Los Angeles, California, United States

Hem-Onc Associates of the Treasure Coast

Port Saint Lucie, Florida, United States

Moffitt Cancer Center

Tampa, Florida, United States

Emory University

Atlanta, Georgia, United States

Massachusetts General Hospital

Boston, Massachusetts, United States

Washington University School of Medicine

St Louis, Missouri, United States

New York Cancer and Blood Specialists

Port Jefferson Station, New York, United States

Key Dates

Start Date

March 4, 2022

Primary Completion Date

December 30, 2025

Completion Date

September 30, 2026

Last Updated

April 20, 2025

Enrollment

ESTIMATED participants

Conditions

Breast Cancer

Interventions

RGT-419B

DRUG

RGT-419B in combination with hormonal therapy

DRUG

Contacts

Joanna Dojillo, MSc

CONTACT

617-315-9070 joanna.dojillo@regor.com

Regor Pharmaceuticals Central Office

CONTACT

617-315-9070 rgt-419b_01-101@regor.com

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Data Source & Attribution

This clinical trial information is sourced from ClinicalTrials.gov, a service of the U.S. National Institutes of Health.

ClinicalTrials.gov last update: April 20, 2025Data synced to Clareo: March 29, 2026

Modifications: This data has been reformatted for display purposes. Eligibility criteria have been parsed into inclusion/exclusion sections. Location data has been geocoded to enable distance-based search. For the authoritative and most current information, please visit ClinicalTrials.gov.

Neither the United States Government nor Clareo Health make any warranties regarding the data. Check ClinicalTrials.gov frequently for updates.

View ClinicalTrials.gov Terms and Conditions

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

Inclusion Criteria

Exclusion Criteria

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