Sionna Therapeutics Inc.’s approach with small molecules in cystic fibrosis (CF) yielded the Boston-based firm an upsized and oversubscribed $182 million series C financing. The company is working on drugs that could fully restore the function of the CF transmembrane conductance regulator protein by stabilizing the first nucleotide-binding domain (NBD1). Four compounds are expected to enter the clinic this year – three NBD1 stabilizers and one ICL4 modulator.