When metformin, empty nanocapsules, and MET nanocapsules were administered to hPASMCs from healthy controls and patients with heritable PAH at varying concentrations (Figure 2B), we observed that 0.2–0.3 mM MET nanocapsules considerably inhibited the viability of hPASMCs, particularly those from patients harboring BMPR2 p.R899X (Figure 2C). Here, BMPR2 is linked to pulmonary arterial hypertension.