Part 1 (Dose Escalation): This part will evaluate the safety and pharmacokinetics (PK) of a range of doses of OP-1250 administered orally (PO) every day (QD) to subjects in combination with either 600 mg of ribociclib administered PO QD (Treatment Group 1) or with 300 mg of alpelisib administered PO QD (Treatment Group 2) to determine the recommended phase 2 dose (RP2D). The dose escalation phase will evaluate 3 to 6 subjects per cohort who are sequentially enrolled and monitored for DLTs during the first cycle of study treatment. Each cohort will be reviewed for safety, PK, and dose-limiting toxicity DLTs. The DLT observation may be extended to 2 cycles.~Part 2 (Dose Expansion): This part of the study will further evaluate the safety and PK of OP-1250 at the RP2D in combination with either ribociclib (Treatment Group 1) or alpelisib (Treatment Group 2) and provide an exploratory estimate of anti-tumor activity of the combinations.
This is a Phase 1b open-label, 2-part study in 2 treatment groups. The 2 treatment groups are as follows:~Treatment Group 1: OP-1250 in combination with ribociclib (KISQALI®, Novartis Pharmaceuticals Corporation).~Treatment Group 2: OP-1250 in combination with alpelisib (PIQRAY®, Novartis Pharmaceuticals Corporation).