UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 9, 2026 RHYTHM PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38223 46-2159271 (IRS Employer Identification Number) (State or other jurisdiction of incorporation) (Commission File Number) 222 Berkeley Street 12th Floor Boston, MA 02116 (Address ...