Study to Evaluate the Safety, Tolerability, Pharmacokinetics and Preliminary Efficacy of CYH33 in Patients With PIK3CA-related Overgrowth Spectrum (PROS) and PIK3CA-related Vascular Malformations (PRVM)

CYH33: Participants will receive oral CYH33 once daily. The starting dose for adults in Phase I is 10 mg QD; adolescents begin at 5 mg QD. In Phase II, patients will receive RP2D determined in the Phase I study.

Placebo: Matching placebo tablets will be administered once daily during the double-blind period of the Phase II PRVM cohort. Patients randomized to placebo will switch to CYH33 at the end of the blinded phase.