Sionna Therapeutics (SION) investor relations material

Key strategic focus and scientific background

• Focused on cystic fibrosis, aiming to revolutionize treatment with differentiated NBD1 stabilizers in novel combinations to improve CFTR function and patient outcomes.

• NBD1 is a historically challenging target, previously considered undruggable, but breakthroughs were achieved using structural biology and X-ray crystallography.

• The company leverages a validated CF-HBE assay to predict clinical efficacy, supporting both add-on and dual combination strategies.

• Two-thirds of CF patients on standard care do not achieve normal CFTR function, highlighting significant unmet need.

• The commercial opportunity is substantial, with the CF market projected to grow from $12 billion to $15 billion by decade's end.

Pipeline, clinical strategy, and trial design

• Advancing two NBD1 stabilizers: SION-719 (add-on to Trikafta) and SION-451 (anchor for dual combination with SION-2222 or SION-109).

• Both programs showed favorable phase I safety and PK profiles, exceeding exposure targets for clinical benefit.

• PreciSION CF study (SION-719 add-on) and healthy volunteer dual combination study (SION-451) are ongoing, with data expected mid-2026.

• The PreciSION CF study uses a two-way crossover design, enrolling Trikafta patients with typical responses but not already normalized sweat chloride.

• The primary endpoint is a 10 mmol/L sweat chloride improvement, serving as proof of concept for NBD1 biology and assay translation.

Safety, differentiation, and forward-looking plans

• Both SION-719 and SION-451 demonstrated favorable safety and tolerability in phase I, with no specific safety concerns for NBD1 or CFTR.

• Drug-drug interaction risks have been carefully evaluated, with complementary modulators selected for differentiated metabolic profiles.

• SION-719 is more potent at lower doses, making it suitable for add-on use, while SION-451 achieves higher exposures, favoring dual combination efficacy.

• No potentiator is required for NBD1 stabilization, though one is available in the pipeline for potential lifecycle management.

• Strong financial position with $310 million in cash at end-2025, providing runway into 2028 and flexibility for future strategic decisions.