Rezubio Pharmaceuticals advanced RZ-520 into Phase I for chronic respiratory diseases after receiving IND clearances from both the FDA and China’s NMPA. The company said dosing is underway in a Phase I healthy-volunteer trial. RZ-520 is positioned for respiratory indications, and dual-region IND clearance suggests early data generation is aligned for both U.S. and China regulatory tracks. For respiratory-focused developers, the update is notable because it shortens the path to first clinical pharmacology readouts and potentially accelerates later global partnering opportunities.