Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 336

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 336
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, which was recorded as research and development expense in the consolidated statements of operations and comprehensive loss
because the acquired license represented in-process research and development with no alternative future use. In addition, the Company is required to pay Sanofi a total of up to $40.0 million upon
achievement of certain late-stage developmental and commercial milestones. The developmental milestone payment will be recorded when the milestone is achieved, and the commercial milestone payment and royalties will be recorded when the sales occur.
As of December 31, 2023, none of such milestones have been achieved. The Company is also required to pay royalties to Sanofi in the low single-digit percentage range based on net sales of licensed products, subject to customary reductions and
offsets. Such royalty payments shall be reduced for products covered by derived patents.

CFF Payment Agreement

In December 2019, the Company entered into a payment agreement (the “CFF Payment Agreement”) with the Cystic Fibrosis Foundation
(“CFF”), pursuant to which the Company agreed to provide CFF with compensation in exchange for the grant of, or forbearance from exercising, certain of CFF’s rights existing under the license agreement by and between CFF (through an
assignment by Cystic Fibrosis Foundation Therapeutics, Inc.) and Genzyme Corporation, an affiliate of Sanofi (the “CFFT-Genzyme Agreement”). Under the CFF Payment Agreement, the Company is obligated
to compensate CFF in connection with the Company’s development and commercialization of licensed products under the Sanofi License Agreement.

As initial consideration for CFF’s grant of, and forbearance from exercising, its rights under the
CFFT-Genzyme Agreement, the Company paid an upfront fee of $0.2 million and issued CFF 300,300 shares of its Series Seed preferred stock, valued at $1.0 million. In addition, the Company agreed
to pay CFF a sub-teen double-digit percentage of any amounts paid by it to Sanofi under the Sanofi License Agreement, other than milestone, royalty or reimbursement payments. In addition, the

F-20

Company is required to pay CFF a total of up to $40.0 million upon achievement of certain late-stage developmental and commercial milestones. Such milestone and royalty payments shall be
reduced for products covered by derived patents. Further, a side letter was executed between the Company and Sanofi, which clarifies the relationship between the Company, Sanofi and CFF, under