Sionna Therapeutics disclosed that its cystic fibrosis add-on strategy failed in a Phase 2 trial, after the company tested the NBD1 stabilizer SION-719 in combination with Vertex’s Trikafta. The regimen did not deliver a statistically significant improvement in sweat chloride versus Trikafta alone, a key readout for CF pharmacology. The data triggered a sharp market response and pushed Sionna to reassess next steps while preserving cash. The trial result removes a potential challenger to Vertex’s CF franchise and highlights the difficulty of translating CFTR-modulator gains into meaningful incremental benefit. In a separate Phase 3 development, Tenax Therapeutics reported negative results for TNX-103 in pulmonary hypertension associated with heart failure with preserved ejection fraction, failing the primary endpoint of change in six-minute walk distance. The trial did not achieve statistical significance, even as Tenax pointed to biomarker signals and subgroup hints. For investors and trial operators, both readouts reinforce the importance of endpoint selection, placebo response management, and differentiation claims that are tied to clinically meaningful effect sizes.