Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 174

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 174
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”) studies to evaluate the interaction of SION-719 and SION-451 with the NBD1 domain, and CFTR western blot
analysis to assess the impact of NBD1 stabilizers on the folding, maturation and stability of F508del-CFTR. Given the results of these preclinical studies, we believe that we have identified highly potent NBD1 stabilizers with robust preclinical
activity.

SION-719and SION-451Increased NBD1 Thermal Stability

In preclinical studies, SION-719 and SION-451 increased the
stability of the NBD1 domain as measured using DSLS experiments. Light scattering provides a measure of the temperature at which a protein unfolds. As the temperature rises, the CFTR protein unfolds and creates aggregates that interfere with the
passage of light. These preclinical studies evaluated the change in temperature that the protein aggregated as the ratio of the compound to CFTR protein increased, which is an indicator of stability. We also evaluated ETI in these preclinical
studies, and we found that they had no effect on NBD1 thermal stability, as measured by light scattering techniques. Restoration of NBD1 thermal stability has been highlighted as being both necessary and sufficient to correct F508del CFTR folding
and assembly. Both SION-719 (Figure 19, left) and SION-451 (Figure 19, right) increased F508del-NBD1 stability by approximately 16°C. These preclinical models show
the ability of SION-719 and SION-451 to improve the stability of NBD1 as compared to ETI, as measured by light scattering techniques.

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Figure 19. SION-719and SION-451Increased Stability of the NBD1 Domain

SION-719and SION-451Bound to NBD1 with High Affinity

To evaluate the binding ability of our stabilizer candidates, we employed SPR studies to evaluate the interaction of SION-719 and SION-451 with the NBD1 domain. SPR studies measure changes in the mass of biomolecules immobilized on a metal film. When a small molecule ligand binds to the
immobilized target protein, the refractive index of the metal film changes, resulting in a changed reflection angle of light. In these studies, we found that the strength of the binding interaction was high; the binding affinity of SION-719 to F508del-NBD1 was approximately 4.3 nM and the