LeonaBio, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE

SECURITIES EXCHANGE ACT OF 1934

(AMENDMENT NO. )

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☒ Definitive Proxy Statement

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Dear Fellow Stockholders:

We are pleased to invite you to attend the special meeting of stockholders and any postponement, adjournments or other delays thereof, which we refer to as the Special Meeting of LeonaBio, Inc., a Delaware corporation, or the Company. The Special Meeting will be held on March 18, 2026, at 8:00 a.m., Pacific Time. The Special Meeting will be conducted virtually via live audio webcast. You will be able to attend the Special Meeting virtually by visiting www.virtualshareholdermeeting.com/LONA2026SM, where you will be able to listen to the meeting live, submit questions and vote online. The Special Meeting will be held for the following purposes:

Proposal 1.

To approve the issuance of 5,502,402 shares of common stock, par value $0.0001 per share, or the common stock, pursuant to the exercise of a pre-funded warrant, or the Sermonix Pre-Funded Warrant, held by Sermonix Pharmaceuticals, Inc., or Sermonix, in accordance with Nasdaq Rule 5635(a)(2).

Proposal 2.

To approve the issuance of shares of common stock to Sermonix pursuant to an exercise of the Sermonix Pre-Funded Warrant if, immediately following such exercise, Sermonix, together with its affiliates and any other persons whose beneficial ownership of shares of common stock would be aggregated with Sermonix for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act, would beneficially own in excess of 19.99% of our outstanding common stock, in accordance with Nasdaq Rule 5635(b).

Proposal 3.

To approve the issuance of shares of common stock to Perceptive Advisors or its affiliates pursuant to the exercise of warrants if, immediately following such exercise, Perceptive Advisors, together with its affiliates and any other persons whose beneficial ownership of shares of common stock would be aggregated with Perceptive Advisors for purposes of Section 13(d) of the Exchange Act, would beneficially own in excess of 19.99% of our outstanding common stock, in accordance with Nasdaq Rule 5635(b).

Proposal 4.

To approve the LeonaBio, Inc. 2026 Equity Incentive Plan.

Proposal 5.

To amend our amended and restated certificate of incorporation to increase the number of authorized shares of common stock.

Proposal 6.

To adjourn the Special Meeting, if necessary or appropriate in the view of the board of directors, including to solicit additional proxies if there are insufficient votes at the time of the Special Meeting to adopt any of Proposal 1, Proposal 2, Proposal 3, Proposal 4 or Proposal 5.

These items of business are more fully described in the attached formal meeting notice and proxy statement. The record date for the Special Meeting is January 27, 2026. Only stockholders of record at the close of business on that date are entitled to notice of and may vote at the Special Meeting or any adjournment thereof.

Your vote is important. Whether or not you attend the Special Meeting virtually, it is important that your shares be represented and voted at the Special Meeting. Therefore, we urge you to vote and submit your proxy promptly via the internet, telephone or mail.

On behalf of our board of directors, we would like to express our appreciation for your continued support of and interest in the Company.

Sincerely,

Mark J. Litton, Ph.D.

President and Chief Executive Officer

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

By order of the Board of Directors,

Mark J. Litton, Ph.D.

President and Chief Executive Officer

Bothell, Washington

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE SPECIAL STOCKHOLDER MEETING TO BE HELD ON MARCH 18, 2026.

The proxy statement is available free of charge at www.ProxyVote.com. Information on this website, other than this proxy statement, is not a part of this proxy statement.

Please sign, date and return the enclosed proxy card in the envelope provided, or submit your proxy and voting instructions over the Internet or by telephone by following the instructions on the enclosed proxy card so that you may be represented at the special meeting.

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