# EDGAR Filing Document

**Accession Number:** 0001649904
**File Stem:** 0001628280-26-012403
**Filing Date:** 2026-2
**Character Count:** 19709
**Document Hash:** eb481f91ad63a866372575fa00f536ae
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001628280-26-012403.hdr.sgml**: 20260226

**ACCESSION NUMBER**: 0001628280-26-012403

**CONFORMED SUBMISSION TYPE**: S-8

**PUBLIC DOCUMENT COUNT**: 16

**REFERENCES 429**: 333-220925

**REFERENCES 429**: 333-223647

**REFERENCES 429**: 333-229642

**REFERENCES 429**: 333-236829

**REFERENCES 429**: 333-253709

**REFERENCES 429**: 333-263168

**REFERENCES 429**: 333-270231

**REFERENCES 429**: 333-277539

**REFERENCES 429**: 333-285411

**FILED AS OF DATE**: 20260226

**DATE AS OF CHANGE**: 20260226

**EFFECTIVENESS DATE**: 20260226

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** RHYTHM PHARMACEUTICALS, INC.
- **CENTRAL INDEX KEY:** 0001649904
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 462159271
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** S-8
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-293816
- **FILM NUMBER:** 26690543

**BUSINESS ADDRESS:**
- **STREET 1:** 222 BERKELEY STREET
- **STREET 2:** 12TH FLOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02116
- **BUSINESS PHONE:** 857-264-4280

**MAIL ADDRESS:**
- **STREET 1:** 222 BERKELEY STREET
- **STREET 2:** 12TH FLOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02116

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** RHYTHM METABOLIC, INC.
- **DATE OF NAME CHANGE:** 20150803

**As filed with the Securities and Exchange Commission on February 26, 2026**

**Registration No. 333-** 

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

**FORM S-8**

**REGISTRATION STATEMENT**

***UNDER***

***THE SECURITIES ACT OF 1933***

**Rhythm Pharmaceuticals, Inc.**

**(Exact name of registrant as specified in its charter)**

---

| | |
|:---|:---|
| **Delaware** | **46-2159271** |
| **(State or other jurisdiction of incorporation or organization)** | **(I.R.S. Employer Identification No.)** |

---

**222 Berkeley Street**

**12th Floor**

**Boston, MA 02116**

**(857) 264-4280**

**(Address of Principal Executive Offices) (Zip Code)**

**Rhythm Pharmaceuticals, Inc. 2017 Equity Incentive Plan**

**(Full title of the plan)**

**David P. Meeker, M.D.**

**Chief Executive Officer, President and Chairman of the Board**

**Rhythm Pharmaceuticals, Inc.**

**222 Berkeley Street**

**12**<sup>th</sup> **Floor**

**Boston, MA 02116**

**(857) 264-4280**

**(Name and address of agent for service) (Telephone number, including area code, of agent for service)**

***With copies to:***

**Peter N. Handrinos, Esq.**

**Latham & Watkins LLP**

**John Hancock Tower** 

**200 Clarendon Street**

**Boston, MA 02116**

**(617) 948-6060**

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

------

---

| | |
|:---|:---|
| Large accelerated filer ⌧ | Accelerated filer ◻ |
| Non-accelerated filer ◻ | Smaller reporting company ◻ |
| | Emerging growth company ◻ |

---

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 7(a)(2)(B) of Securities Act. ◻

**EXPLANATORY NOTE**

This Registration Statement on Form S-8 is being filed for the purpose of registering an additional 2,688,212 shares of the Registrant's common stock to be issued pursuant to the Rhythm Pharmaceuticals, Inc. 2017 Equity Incentive Plan (the "Incentive Plan"). A Registration Statement of the Registrant on Form S-8 relating to the Incentive Plan is effective.

**INCORPORATION BY REFERENCE OF CONTENTS OF REGISTRATION STATEMENTS ON FORM S-8**

The contents of the Registration Statements on Form S-8 (File Nos. <u>[333-220925](https://www.sec.gov/Archives/edgar/data/1649904/000110465917061965/a17-23051_1s8.htm)</u>, <u>[333-223647](https://www.sec.gov/Archives/edgar/data/1649904/000110465918017477/a18-6648_1s8.htm)</u>, <u>[333-229642](https://www.sec.gov/Archives/edgar/data/1649904/000110465919007907/a19-4560_1s8.htm)</u>, <u>[333-236829](https://www.sec.gov/Archives/edgar/data/1649904/000110465920027924/tm2011031-1_s8.htm)</u>, <u>[3](https://www.sec.gov/Archives/edgar/data/1649904/000110465921030005/tm218067d1_s8.htm)[33-253709](https://www.sec.gov/Archives/edgar/data/1649904/000110465921030005/tm218067d1_s8.htm)</u>, <u>[333-263168](https://www.sec.gov/Archives/edgar/data/1649904/000110465922028778/tm227881d2_s8.htm)</u>, <u>[333-270231](https://www.sec.gov/Archives/edgar/data/1649904/000110465923027957/tm237899d1_s8.htm)</u>, <u>[333-277539](https://www.sec.gov/Archives/edgar/data/1649904/000110465924029422/tm247388d1_s8.htm)</u>, and <u>[333-285411](https://www.sec.gov/Archives/edgar/data/1649904/000155837025001935/tmb-20250228xs8.htm)</u>, including any amendments thereto, filed with the Securities and Exchange Commission, relating to the Incentive Plan, are incorporated herein by reference.

**Item 8. Exhibits**

---

| | |
|:---|:---|
| **Exhibit**<br> Number | **Description** |
| 4.1 | <u>[Amended and Restated Certificate of Incorporation of Rhythm Pharmaceuticals, Inc.](https://www.sec.gov/Archives/edgar/data/1649904/000155837025008924/rytm-20250624xex3d1.htm)[and Certificate of Amendment](https://www.sec.gov/Archives/edgar/data/1649904/000155837025008924/rytm-20250624xex3d1.htm)[(incorporated by reference to Exhibit 3.1 to Rhythm Pharmaceuticals, Inc.'s Current Report on Form 8-K (File No. 001-38223) filed on June 26, 2025)](https://www.sec.gov/Archives/edgar/data/1649904/000155837025008924/rytm-20250624xex3d1.htm)</u> |
| 4.2 | <u>[Amended and Restated Certificate of Designations of Rhythm Pharmaceuticals, Inc. (incorporated by reference to Exhibit 3.4 to Rhythm Pharmaceuticals, Inc.'s Quarterly Report on Form 10-Q (File No. 001 38223) filed on May 7, 2024)](https://www.sec.gov/Archives/edgar/data/1649904/000155837024007076/rytm-20240331xex3d4.htm)</u> |
| 4.3 | <u>[Amended and Restated Bylaws of Rhythm Pharmaceuticals, Inc. (incorporated by reference to Exhibit 3.1 to Rhythm Pharmaceuticals, Inc.'s Current Report on Form 8-K (File No. 001-38223) filed on December 18, 2023)](https://www.sec.gov/Archives/edgar/data/1649904/000110465923126873/tm2332524d2_ex3-1.htm)</u> |
| 5.1\* | <u>[O](rytm-51opinionclean.htm)[pinion of Latham & Watkins LLP](rytm-51opinionclean.htm)</u> |
| 23.1\* | <u>[Consent of Ernst & Young LLP, Independent Registered Public Accounting Firm](rytm-20260226xex231.htm)</u> |
| 23.2\* | <u>[Consent of Latham & Watkins LLP (included in Exhibit 5.1)](rytm-51opinionclean.htm)</u> |
| 24.1\* | <u>[Power of Attorney (included on signature page)](#idead54511a854df9a588219469294711_34)</u> |
| 99.1 | <u>[Rhythm Pharmaceuticals, Inc. 2017 Equity Incentive Plan and Form of Option Agreement (incorporated by reference to Exhibit 10.2 to Rhythm Pharmaceuticals, Inc.'s Quarterly Report on Form 10-Q (File No. 001-38223) filed on November 14, 2017)](https://www.sec.gov/Archives/edgar/data/1649904/000155837017008882/rytm-20170930ex102a02cce.htm)</u> |
| 99.2 | <u>[2017 Equity Incentive Plan Form of Restricted Stock Unit Award Agreement (incorporated by reference to Exhibit 10.18 to Rhythm Pharmaceuticals, Inc.'s Annual Report on Form 10-K (File No. 001-38223) filed on March 2, 2020)](https://www.sec.gov/Archives/edgar/data/1649904/000155837020001896/rytm-20191231ex101831313.htm)</u> |
| 99.3 | <u>[2017 Equity Incentive Plan Performance Unit Agreement (incorporated by reference to Exhibit 10.4 to Rhythm Pharmaceuticals, Inc.'s Quarterly Report on Form 10 Q (File No. 001 38223) filed on May 7, 2024)](https://www.sec.gov/Archives/edgar/data/1649904/000155837024007076/rytm-20240331xex10d4.htm)</u> |
| 107.1\* | <u>[Filing Fee Table](ex1071filingfees.htm)</u> |

---

\* Filed herewith.

------

**SIGNATURES**

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston, Commonwealth of Massachusetts, on February 26, 2026.

---

| | |
|:---|:---|
| **RHYTHM PHARMACEUTICALS, INC.** | **RHYTHM PHARMACEUTICALS, INC.** |
| By: | /s/ David P. Meeker, M.D. |
|  | David P. Meeker, M.D. |
|  | *Chief Executive Officer, President and Chairman of the Board* |

---

**POWER OF ATTORNEY**

Each person whose signature appears below hereby constitutes and appoints David P. Meeker, M.D. and Hunter C. Smith, or each of them singly, with full power to act without the other, such person's true and lawful attorneys-in-fact and agents, with full power of substitution and re-substitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign this registration statement and any and all amendments, including post-effective amendments to this registration statement, and to file the same, with exhibits and schedules thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary or desirable to be done in connection therewith as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or any of them, or their or his or her substitute or substitutes may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the date indicated.

---

| | | |
|:---|:---|:---|
| **Signature** | **Title** | **Date** |
| /s/ David P. Meeker, M.D. | Chief Executive Officer, President and Director | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026  |
| David P. Meeker, M.D. | (Principal Executive Officer) |  |
| /s/ Hunter C. Smith | Chief Financial Officer | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026  |
| Hunter C. Smith | (Principal Financial Officer) |  |
| /s/ Christopher P. German | Corporate Controller | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026  |
| Christopher P. German | (Principal Accounting Officer) |  |
| /s/ Edward T. Mathers | Lead Director | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026  |
| Edward T. Mathers |  |  |
| /s/ Stuart Arbuckle | Director | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026  |
| Stuart Arbuckle |  |  |
| /s/ Jennifer L. Good | Director | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026 |
| Jennifer L. Good |  |  |
| /s/ Christophe R. Jean | Director | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026 |
| Christophe R. Jean |  |  |
| /s/ David W. J. McGirr | Director | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026 |
| David W. J. McGirr |  |  |
| /s/ Lynn A. Tetrault, J.D. | Director | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;February 26, 2026 |
| Lynn A. Tetrault, J.D. |  |  |

---

------

## Ex-Filing

?xml version='1.0' encoding='ASCII'? EX-FILING FEES

---

| |
|:---|
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Calculation of Filing Fee Tables**  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **S-8**  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **RHYTHM PHARMACEUTICALS, INC.**  |

---

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Security Type**  | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Security Class Title**  | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Fee Calculation Rule**  | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Amount Registered**  | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Proposed Maximum Offering Price Per Unit**  | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Maximum Aggregate Offering Price**  | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Fee Rate**  | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **Amount of Registration Fee**  |
| Equity | Common Stock, par value $0.001 per share | 457(a) | 2688212 | $97.35 | $261697438.20 | 0.0001381 | $36140.42 |
| Total Offering Amounts: | Total Offering Amounts: | Total Offering Amounts: | Total Offering Amounts: |  | $261697438.20  |  | $36140.42  |
| Total Fee Offsets:  | Total Fee Offsets:  | Total Fee Offsets:  | Total Fee Offsets:  |  |  |  | $0.00  |
| Net Fee Due:  | Net Fee Due:  | Net Fee Due:  | Net Fee Due:  |  |  |  | $36140.42  |

---

---

| | |
|:---|:---|
| | |
| **Rule 457(p)** | **Rule 457(p)** |
| Fee Offset Claims | N/A |
| Fee Offset Sources | N/A |

---

## Exhibit 5.1

![](rytm-51opinionclean001.jpg)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;US-DOCS\168479110.2 200 Clarendon Street Boston, Massachusetts 02116 Tel: +1.617.948.6000 Fax: +1.617.948.6001 www.lw.com FIRM / AFFILIATE OFFICES Austin Milan Beijing Munich Boston New York Brussels Orange County Century City Paris Chicago Riyadh Dubai San Diego Düsseldorf San Francisco Frankfurt Seoul Hamburg Shanghai Hong Kong Silicon Valley Houston Singapore London Tel Aviv Los Angeles Tokyo Madrid Washington, D.C. February 26, 2026 Rhythm Pharmaceuticals, Inc. 222 Berkeley Street, 12th Floor Boston, Massachusetts 02116 Re: Registration Statement on Form S-8; 2,688,212 shares of Common Stock, par value $0.001 per share, of Rhythm Pharmaceuticals, Inc. To the addressee set forth above: We have acted as special counsel to Rhythm Pharmaceuticals, Inc., a Delaware corporation (the "Company"), in connection with the preparation and filing by the Company with the Securities and Exchange Commission of a registration statement on Form S–8 (the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), relating to the issuance of up to 2,688,212 shares of the Company's common stock, par value $0.001 per share (the "Shares"), which may be issued pursuant to the Rhythm Pharmaceuticals, Inc. 2017 Equity Incentive Plan (the "2017 Plan"). This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or the prospectus forming a part thereof, other than as expressly stated herein with respect to the issuance of the Shares. As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon the foregoing and upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein only as to the General Corporation Law of the State of Delaware, as amended (the "DCGL"), and we express no opinion with respect to any other laws. Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, when the Shares shall have been duly registered on the books of the transfer agent and registrar therefor in the name or on behalf of the recipients thereof, and have been issued by the Company for legal consideration in excess of par value in the circumstances contemplated by the 2017 Plan, assuming in each case that the individual grants or awards under the 2017 Plan are duly authorized by all necessary corporate action and duly granted or awarded and exercised in accordance with the requirements of law and the 2017 Plan (and the agreements and awards duly adopted thereunder and in accordance therewith), the issue and sale of the

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![](rytm-51opinionclean002.jpg)

February 26, 2026 Page 2 US-DOCS\168479110.2 Shares will have been duly authorized by all necessary corporate action of the Company, and the Shares will be validly issued, fully paid and nonassessable. In rendering the foregoing opinion, we have assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the DGCL. This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Securities Act. We consent to your filing this opinion as an exhibit to the Registration Statement. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Securities and Exchange Commission thereunder. Sincerely, /s/ Latham & Watkins LLP

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## Exhibit 23.1

**Exhibit 23.1**

**Consent of Independent Registered Public Accounting Firm**

We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the Rhythm Pharmaceuticals, Inc. 2017 Equity Incentive Plan of our reports dated February 26, 2026, with respect to the consolidated financial statements of Rhythm Pharmaceuticals, Inc. and the effectiveness of internal control over financial reporting of Rhythm Pharmaceuticals, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2025, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Boston, Massachusetts

February 26, 2026

<br>