United States securities and exchange commission logo June 13, 2022 Pablo J. Cagnoni, M.D. Chief Executive Officer Rubius Therapeutics, Inc. 399 Binney Street, Suite 300 Cambridge, MA 02139 Re: Rubius Therapeutics, Inc. Registration Statement on Form S-3 Filed June 8, 2022 File No. 333-265482 Dear Dr. Cagnoni: This is to advise you that we have not reviewed and will not review your registration statement. Please refer to Rules 460 and 461 regarding requests for acceleration. We remind you that the company and its management are responsible for the accuracy and adequacy of their disclosures, notwithstanding any review, comments, action or absence of action by the staff. Please contact Tyler Howes at 202-551-3370 with any questions. Sincerely, Division of Corporation Finance Office of Life Sciences cc: Yasin Akbari, Esq.