X0202 SCHEDULE 13G/A 0001647491 XXXXXXXX LIVE 2 Class A common stock, $0.01 par value per share 03/31/2026 0001380106 Rapid Micro Biosystems, Inc. 75340L104 25 Hartwell Avenue Lexington MA 02421 Rule 13d-1(d) Longitude Capital Partners II, LLC b DE 0 3529245 0 3529245 3529245 N 8.6 OO All such shares are held of record by LVPII (as defined in the Explanatory Note below). LCPII (as defined in the Explanatory Note below) is the general partner of LVPII and may be deemed to have voting and dispositive power with respect to these securities. Patrick G. Enright and Juliet Tammenoms Bakker are the managing members of LCPII and may each be deemed to share voting and dispositive power with respect to these securities. Based on 41,267,511 shares of Class A Common Stock, outstanding as of March 31, 2026, as reported by the Issuer in the definitive proxy statement on Schedule 14A, filed with the United States Securities and Exchange Commission (the Commission) on April 8, 2026 (the Proxy Statement). Longitude Venture Partners II, L.P. b DE 0 3529245 0 3529245 3529245 N 8.6 PN All such shares are held of record by LVPII. LCPII is the general partner of LVPII and may be deemed to have voting and dispositive power with respect to these securities. Patrick G. Enright and Juliet Tammenoms Bakker are the managing members of LCPII and may each be deemed to share voting and dispositive power with respect to these securities. Based on 41,267,511 shares of Class A Common Stock, outstanding as of March 31, 2026, as reported by the Issuer in the Proxy Statement. Longitude Prime Partners, LLC b DE 0 0 0 0 0 N 0 OO Longitude Prime Fund, L.P. b DE 0 0 0 0 0 N 0 PN Patrick G. Enright b X1 0 3529245 0 3529245 3529245 N 8.6 IN All such shares are held of record by LVPII. LCPII is the general partner of LVPII and may be deemed to have voting and dispositive power with respect to these securities. Patrick G. Enright and Juliet Tammenoms Bakker are the managing members of LCPII and may each be deemed to share voting and dispositive power with respect to these securities. Based on 41,267,511 shares of Class A Common Stock, outstanding as of March 31, 2026, as reported by the Issuer in the Proxy Statement. Juliet Tammenoms Bakker b DE 0 3529245 0 3529245 3529245 N 8.6 IN All such shares are held of record by LVPII. LCPII is the general partner of LVPII and may be deemed to have voting and dispositive power with respect to these securities. Patrick G. Enright and Juliet Tammenoms Bakker are the managing members of LCPII and may each be deemed to share voting and dispositive power with respect to these securities. Based on 41,267,511 shares of Class A Common Stock, outstanding as of March 31, 2026, as reported by the Issuer in the Proxy Statement. Rapid Micro Biosystems, Inc. 25 Hartwell Avenue, Lexington, MA 02421 Explanatory Note: This Amendment No. 2 ("Amendment No. 2") amends and supplements the Schedule 13G initially filed with the Commission on February 15, 2022, as amended by Amendment No. 1 filed with the Commission on February 14, 2023 (the "Original Schedule 13G") and is being filed by Longitude Capital Partners II, LLC ("LCPII"), Longitude Venture Partners II, L.P. ("LVPII"), Longitude Prime Partners, LLC ("LPP") and Longitude Prime Fund, L.P. ("LPF" and together with LCPII, LVPII and LPP, the "Reporting Entities") and Patrick G. Enright and Juliet Tammenoms Bakker (together, the "Reporting Individuals"). The Reporting Entities and the Reporting Individuals are collectively referred to as the "Reporting Persons." The agreement among the Reporting Persons to file jointly in accordance with the provisions of Rule 13d-1(k)(1) under the Act is filed as Exhibit 1 to the Original Schedule 13G. Only those items that are hereby reported are amended; all other items reported in the Original Schedule 13G remain unchanged. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable. Capitalized terms not defined in this Amendment No. 2 have the meanings ascribed to them in the Original Schedule 13G. The address of the principal business office of each Reporting Person is 2740 Sand Hill Road, 2nd Floor, Menlo Park, CA 94025. Each of LCPII and LPP is a limited liability company organized under the laws of the State of Delaware. Each of LVPII and LPF is a limited partnership organized under the laws of the State of Delaware. Each of the Reporting Individuals is a citizen of the United States of America. Y See Row 9 of the cover page for each Reporting Person and the corresponding footnotes. Except to the extent of his, her or its pecuniary interest therein, each Reporting Person disclaims beneficial ownership of such shares of Class A Common Stock, except for the shares, if any, such Reporting Person holds of record. See Row 11 of the cover page for each Reporting Person and the corresponding footnotes. Except to the extent of his, her or its pecuniary interest therein, each Reporting Person disclaims beneficial ownership of such shares of Class A Common Stock, except for the shares, if any, such Reporting Person holds of record. See Row 5 of the cover page for each Reporting Person and the corresponding footnotes. Except to the extent of his, her or its pecuniary interest therein, each Reporting Person disclaims beneficial ownership of such shares of Class A Common Stock, except for the shares, if any, such Reporting Person holds of record. See Row 6 of the cover page for each Reporting Person and the corresponding footnotes. Except to the extent of his, her or its pecuniary interest therein, each Reporting Person disclaims beneficial ownership of such shares of Class A Common Stock, except for the shares, if any, such Reporting Person holds of record. See Row 7 of the cover page for each Reporting Person and the corresponding footnotes. Except to the extent of his, her or its pecuniary interest therein, each Reporting Person disclaims beneficial ownership of such shares of Class A Common Stock, except for the shares, if any, such Reporting Person holds of record. See Row 8 of the cover page for each Reporting Person and the corresponding footnotes. Except to the extent of his, her or its pecuniary interest therein, each Reporting Person disclaims beneficial ownership of such shares of Class A Common Stock, except for the shares, if any, such Reporting Person holds of record. Y N Under certain circumstances set forth in the limited partnership agreements of each of LVPII and LPF and the limited liability company agreement of each of LCPII and LPP, the general and limited partners or members, as the case may be, of each of such entities may be deemed to have the right to receive dividends from, or the proceeds from, the sale of securities of the Issuer owned by each such entity of which they are a partner or member, as the case may be. Y Y Y Y Longitude Capital Partners II, LLC /s/ Cristiana Blauth Oliveira 05/15/2026 Longitude Venture Partners II, L.P. /s/ Cristiana Blauth Oliveira 05/15/2026 Longitude Prime Partners, LLC /s/ Cristiana Blauth Oliveira 05/15/2026 Longitude Prime Fund, L.P. /s/ Cristiana Blauth Oliveira 05/15/2026 Patrick G. Enright /s/ Cristiana Blauth Oliveira 05/15/2026 Juliet Tammenoms Bakker /s/ Cristiana Blauth Oliveira 05/15/2026