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

NCT05304962 | Recruiting Phase 1 FDA Drug

• 1 other identifier: RGT-419B_01-101
• Study Type: interventional
• Target: 64
• Locations: 1 country
• Sites: 8

Brief 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.

Conditions

Breast Cancer

Keywords

Breast Cancer

Outcome Measures

Primary Outcomes (1)

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

  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.

  4 weeks (1 cycle)

Secondary Outcomes (10)

• Safety & Tolerability - Incidence, Severity, and Causality of all Treatment Emergent Adverse Events (TEAEs)

  through study completion, an average of 1 year

• Day 1 and steady-state PK assessment of RGT-419B and major metabolites - Cmax

  through study completion, an average of 1 year

• Day 1 and steady-state PK assessment of RGT-419B and major metabolites - Area Under Concentration-Time Curve (AUC0-t)

  through study completion, an average of 1 year

• Day 1 and steady-state PK assessment of RGT-419B and major metabolites - Area Under Concentration-Time Curve to Infinity (AUC0-inf)

  through study completion, an average of 1 year

• Day 1 and steady-state PK assessment of RGT-419B and major metabolites - Plasma Decay Half-Life (t 1/2)

  through study completion, an average of 1 year

Other Outcomes (1)

• Symptom Burden

  through study completion, an average of 1 year

Study Arms (2)

Arm A

EXPERIMENTAL

RGT-419B given alone as monotherapy

Drug: RGT-419B

Arm B

EXPERIMENTAL

RGT-419B in combination with Hormonal Therapy

Drug: RGT-419B in combination with hormonal therapy

Interventions

RGT-419B DRUG

oral capsules

Arm A

RGT-419B in combination with hormonal therapy DRUG

RGT-419B in combination with hormonal therapy (Selective Estrogen Receptor Degrader, Selective Estrogen Receptor Modulator, or Aromatase Inhibitor)

Arm B

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Male or female \>/= 18 years old
• ECOG Performance Status 0 to 1
• 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.
• Measurable AND evaluable lesions at baseline per RECIST v1.1.
• 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
• Adequate organ function
• Ability to understand and the willingness to sign a written informed consent document

You may not qualify if:

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

Sponsors & Collaborators

• Regor Pharmaceuticals Inc.: lead

Study Sites (8)

University of California, San Diego

La Jolla, California, 92037, United States

RECRUITING

University California, Los Angeles

Los Angeles, California, 90404, United States

RECRUITING

Hem-Onc Associates of the Treasure Coast

Port Saint Lucie, Florida, 34952, United States

ACTIVE NOT RECRUITING

Moffitt Cancer Center

Tampa, Florida, 33612, United States

RECRUITING

Emory University

Atlanta, Georgia, 30322, United States

RECRUITING

Massachusetts General Hospital

Boston, Massachusetts, 02142, United States

RECRUITING

Washington University School of Medicine

St Louis, Missouri, 63110, United States

RECRUITING

New York Cancer and Blood Specialists

Port Jefferson Station, New York, 11776, United States

RECRUITING

MeSH Terms

Conditions

Breast Neoplasms

Condition Hierarchy (Ancestors)

Neoplasms by Site; Neoplasms; Breast Diseases; Skin Diseases; Skin and Connective Tissue Diseases

Central Study 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

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SEQUENTIAL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Model Details: There will be two study arms opened sequentially to the same patient population. Arm A is RGT-419B alone (singlet). Arm B is RGT-419B + Hormonal Therapy (doublet) and will follow completion of Arm A.

Study Record Dates

• First Submitted: February 24, 2022
• First Posted: March 31, 2022
• Study Start: March 4, 2022
• Primary Completion (Estimated): September 30, 2026
• Study Completion (Estimated): December 30, 2026
• Last Updated: April 2, 2026

Record last verified: 2026-03

Locations

US (8)