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): October 31, 2017

RHYTHM PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Delaware		001-38223		46-2159271
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification Number)

500 Boylston Street, 11th Floor

Boston, MA 02116

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: (857) 264-4280

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. x

Item 8.01 Other Events

On October 31, 2017, Rhythm Pharmaceuticals, Inc. (the “Company”) issued the attached press release regarding preliminary data from an ongoing Phase 2 proof-of-concept study evaluating the safety and efficacy of setmelanotide, the Company’s novel melanocortin-4 receptor (MC4R) agonist, for the treatment of Bardet-Biedl syndrome (BBS). Results are being presented at the ObesityWeek 2017 meeting held October 29 — November 2, 2017 in Washington D.C.

Item 9.01 Financial Statements and Exhibits.

Exhibit No.		Description

99.1		Press release dated October 31, 2017, filed herewith.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	RHYTHM PHARMACEUTICALS, INC.

Date: November 1, 2017	By:	/s/ Hunter Smith
		Hunter Smith
		Chief Financial Officer