Rhythm Pharmaceuticals, Inc.

Item 2.02. Results of Operations and Financial Condition. On August 4, 2026, Rhythm Pharmaceuticals, Inc. (the “Company”) announced its financial results for the second quarter ended June 30, 2026. The full text of the press release issued by the Company in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K (the “Current Report”). The information contained in Item 2.02 of this Current Report (including Exhibit 99.1 attached hereto) shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act, except as expressly provided by specific reference in such a filing.

Item 7.01. Regulation FD Disclosure. On August 4, 2026, the Company also issued a press release and published a presentation announcing preliminary data from its ongoing Phase 2 trial evaluating RM-718 in patients with acquired hypothalamic obesity (HO), which are summarized under Item 8.01 below. The presentation is available in the “Events and Presentations” portion of the Company’s website at ir.rhythmtx.com. A copy of the press release and presentation are furnished as Exhibits 99.2 and 99.3, respectively, to this Current Report on Form 8-K The information contained in Item 7.01 of this Current Report on Form 8-K (including Exhibits 99.1, 99.2 and 99.3 attached hereto) shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act, except as expressly provided by specific reference in such a filing.

Item 8.01. Other Events. On August 4, 2026, the Company announced preliminary data from its ongoing Phase 2 trial evaluating RM-718 in patients with acquired hypothalamic obesity (HO), which are summarized below. Eleven patients with acquired HO were enrolled in the ongoing, open-label trial. Key preliminary findings include: • -11.6% reduction in mean BMI from baseline (n=7) at 16 weeks of RM-718; • RM-718 efficacy results at 16 weeks comparable to mean BMI reduction of -10.1% with bivamelagon (600 mg dose; n=7) at 14 weeks and -10.1% BMI reduction with setmelanotide at 16 weeks (n=64 patients in Phase 2 and 3 trials); and • Two (2) mild instances of hyperpigmentation were reported and were limited to the injection site, with no generalized hyperpigmentation observed. RM-718 was generally well tolerated, with the most common adverse events being injection site reactions, nausea, and vomiting. Eight (8) patients remained on active treatment as of July 16, 2026, including two (2) patients who had not yet reached 16 weeks on therapy. Two participants discontinued treatment due to adverse events: injection site induration and nausea. One patient withdrew from the extension portion of the trial.