Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 304

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 304
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Shares sold by the underwriters to the public will initially be offered at the initial public offering price set forth on the cover of this prospectus. Any shares sold by the underwriters to securities dealers may be sold at a discount of up to $0.756 per share from the initial public offering price. After the initial offering of the shares, the representatives may change the offering price and the other selling terms. The offering of the shares by the underwriters is subject to receipt and acceptance and subject to the underwriters’ right to reject any order in whole or in part. The company and its officers, directors and holders of substantially all of the company’s common stock have agreed with the underwriters, subject to certain exceptions, not to dispose of or hedge any of their common stock or securities convertible into or exchangeable for shares of common stock (the “Lock-UpSecurities”) during the period from the date of this prospectus continuing through the date 180 days after the date of this prospectus, except with the prior written consent of Goldman Sachs & Co. LLC and TD Securities (USA) LLC. See section titled “ Shares Eligible for Future Sale” for a discussion of certain transfer restrictions. 220

The restrictions described in the immediately preceding paragraph do not apply to our officers,
directors and holders of substantially all of our capital stock and securities convertible into or exchangeable for our common stock with respect to:

Transfers of Lock-Up Securities (i) as one or more bona fide gifts or charitable contributions, or for bona
fide estate planning purposes, (ii) upon death by will, testamentary document or intestate succession, (iii) if the lock-up party is a natural person, to any member of the lock-up party’s immediate family or to any trust for the direct or indirect benefit of the lock-up party or the family of the lock-up party or, if the lock-up party is a trust, to a trustor, trustee (or co-trustee) or beneficiary of the trust or the estate of a beneficiary of such trust, (iv) to a corporation, partnership, limited liability company or other entity of which the
lock-up party and the immediate family of the lock-up party are the legal and beneficial owner of all of the outstanding equity securities or similar interests, (v) to a nominee or custodian of a person
or entity to whom a disposition or transfer would be permissible under clauses (i) through (iv) above, (vi) if the lock-up party is a corporation