X0202 SCHEDULE 13D/A 0001193125-21-032496 0001224962 XXXXXXXX LIVE 8 Common Stock, $0.0001 par value 08/22/2026 false 0001620463 04746L203 LeonaBio, Inc.

18706 North Creek Parkway Suite 104 Bothell WA 98011

Alexander Rakitin (646) 205-5345 Perceptive Advisors LLC, 51 Astor Place 10th Floor New York NY 10003 0001224962 N Perceptive Advisors LLC b AF Y DE 0 1889403 0 1889403 1889403 N 19.99 IA 0001164426 N Joseph Edelman b AF Y X1 0 1889403 0 1889403 1889403 N 19.99 IN 0001249675 N Perceptive Life Sciences Master Fund, Ltd. b WC Y E9 0 1559647 0 1559647 1559647 N 16.5 CO 0001851820 N Perceptive Xontogeny Venture Fund II, LP b WC N DE 0 359837 0 359837 359837 N 3.8 PN Common Stock, $0.0001 par value LeonaBio, Inc. 18706 North Creek Parkway Suite 104 Bothell WA 98011 Item 4 of the Schedule 13D is amended and supplemented as follows: On August 22, 2026, Sermonix notified the Reporting Persons that it will distribute Sermonix Pre-Funded Warrants exercisable for 2,352,932 shares of Common Stock to PXV II pursuant to a distribution of securities to owners of Sermonix's common stock. The distribution is expected to be effective on October 26, 2026. Pursuant to the terms of the Sermonix Pre-Funded Warrants, the pre-funded warrants that will be held by PXV II will not be exerciseable to the extent that such exercise would result in beneficial ownership in excess of 19.99% of the outstanding shares of Common Stock of the Issuer. Item 5 of the Schedule 13D is amended and supplemented as follows: The information set forth in rows 11 and 13 of the cover pages to this Schedule 13D is incorporated by reference. The percentages set forth in row 13 are based on an aggregate of 9,421,663 shares of Common Stock outstanding, as disclosed by the Issuer in its Quarterly Report on Form 10-Q filed with the SEC on August 14, 2026, and give effect to the exercise of warrants held by the Reporting Persons for an aggregate of 30,081 shares of Common Stock. The information set forth in rows 7 through 10 of the cover pages to this Schedule 13D is incorporated by reference. Mr. Edelman holds vested stock options to purchase shares of Common Stock in connection with his service as a director of the Issuer; however, such options are not included in the number of shares beneficially owned by Mr. Edelman or the other Reporting Persons because Mr. Edelman agreed on January 13, 2026 that such options cannot be exercised by Mr. Edelman without providing notice to the Issuer of at least 61 days to the extent that such exercise would result in Mr. Edelman or the other Reporting Persons beneficially owning more than 19.99% of the outstanding shares of Common Stock of the Issuer. Pursuant to the terms of the warrants and pre-funded warrants held by the Master Fund and PXV II, the Reporting Persons may not exercise such warrants or pre-funded warrants to the extent that such exercise would result in beneficial ownership in excess of 19.99% of the outstanding shares of Common Stock of the Issuer. As of the date hereof, the Beneficial Ownership Limitation permits the Master Fund or PXV II to exercise warrants and pre-funded warrants for an aggregate of 30,081 shares of Common Stock. None of the Reporting Persons has effected any transaction in shares of Common Stock in the past sixty days. Perceptive Advisors LLC /s/ Joseph Edelman 08/25/2026 Joseph Edelman /s/ Joseph Edelman 08/25/2026 Perceptive Life Sciences Master Fund, Ltd. /s/ Joseph Edelman 08/25/2026 Perceptive Xontogeny Venture Fund II, LP /s/ Joseph Edelman 08/25/2026