Overview
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
Inclusion Criteria:
- 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
- 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);
- Adequate organ function
- Ability to understand and the willingness to sign a written informed consent document
Exclusion Criteria:
- 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