Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 9

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 9
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4 and August 2024, respectively. These trials are randomized, doubled-blinded, placebo-controlled trials designed to evaluate safety, tolerability and PK of
each product candidate. Both trials are being conducted in Australia. In a Part C of each Phase 1 trial, we plan to evaluate the effect of food on the PK of each product candidate and the bioequivalence of a tablet formation compared to the oral
suspension administered in the Phase 1 SAD and MAD trials. We intend to enroll up to 120 healthy volunteers in each trial. We expect topline data for these trials in the first half of 2025.

Interim Phase 1 Trial Data for SION-719

SION-719 was
generally well tolerated at all dose levels administered based on interim Phase 1 clinical data as of the data cutoff date of January 14, 2025. There were no serious adverse events (“SAEs”). Most treatment-emergent adverse events
(“TEAEs”) were mild to moderate (Grade 1 or Grade 2). No TEAEs led to the discontinuation of trial drug. No dose-limiting TEAEs or safety trends of concern have been observed.

Increasing exposure was observed with increasing single and multiple doses. The concentration targets for SION-719 as an add-on to standard of care and
as part of a dual combination with SION-2222 or SION-109 were achieved with single and multiple doses. A PK summary of SION-719 in the MAD portion of the trial is shown in Figure 4 below. The observed PK was consistent with twice daily dosing
(“BID”).

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Figure 4. Preliminary Phase 1 PK Summary for SION-719 in the MAD Portion of the Trial

(Each solid line shows mean concentration data from a dosing cohort on Day 10. Dotted lines represent average PK concentration exposure targets that have the potential, based on our preclinical CFHBE model, to provide clinically meaningful benefit, if SION-719is administered in a proprietary dual combination with either SION-2222or SION-109, or as an add-onto SOC.)

Interim Phase 1TrialData for SION-451

SION-451 was generally well tolerated at all dose levels administered based on interim Phase 1 clinical data as of the data cutoff date of January 14,
2025. SION-451 was generally well tolerated at all dose levels administered. There were no