Participated · Series C · Mar 2024

Sionna Therapeutics is a clinical-stage life sciences company focused on developing treatments for cystic fibrosis by normalizing the function of the CFTR protein. It is advancing a pipeline of small molecules engineered to correct protein defects caused by the ΔF508 mutation. The company holds a portfolio of programs directly targeting correction of the first nucleotide-binding domain (NBD1) and complementary programs targeting ICL4 and TMD1. Its lead approach aims to fully restore ΔF508-CFTR function by stabilizing NBD1. The company raised a $182M Series C to support clinical development and CEO Mike Cloonan said the financing provides funding through 2026 to execute its clinical plan and deliver multiple readouts. Sionna also added Dr. Fleming to its board, bringing more than 30 years of healthcare industry experience. Sionna Therapeutics is a Boston-based life sciences company developing differentiated small-molecule treatments for cystic fibrosis that aim to normalize CFTR function by stabilizing its first nucleotide-binding domain (NBD1). The company is advancing a pipeline of first-in-class small molecules designed to fully restore CFTR function, including programs targeting NBD1 and complementary modulators of the NBD1–ICL4 interface and TMD1. Sionna plans to submit INDs for its first NBD1-targeted program, SION-638, and for its lead ICL4 program, SION-109, within the next 12 months. The company closed a $111M Series B and has raised approximately $150M to date. Management includes CEO Mike Cloonan, CMO Charlotte McKee, and CSO John Macor, with senior discovery and chemistry leaders Greg Hurlbut and Mark Munson. Its board includes representatives from RA Capital, Atlas Venture, OrbiMed and TPG. The new financing will be used to advance development of the NBD1 franchise and complementary modulators.