UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ☒

Filed by a party other than the Registrant ☐

Check the appropriate box:

EQUILLIUM, INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

Equillium C/O TABULATOR, P.O. BOX 8016, CARY, NC 27512-9903 Your vote matters! Meeting Materials: Notice of Meeting and Proxy Statement & Annual Report on Form 10-K Important Notice Regarding the Availability of Proxy Materials for the Stockholders Meeting To Be Held On May 21, 2025 For Stockholders of record as of April 1, 2025 To order paper materials, use one of the following methods. Equillium, Inc. Annual Meeting of Stockholders Wednesday, May 21, 2025 1:00 PM, Pacific Time Annual Meeting to be held virtually via the internet - please visit www.proxydocs.com/EQ for more details You must register to attend the meeting online and/or participate at www.proxydocs.com/EQ. For a convenient way to view proxy materials, VOTE, and obtain directions to attend the meeting go to www.proxydocs.com/EQTo vote your proxy while visiting this site, you will need the control number in the box below. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet or by mail. This is not a ballot. You cannot use this notice to vote your shares. We encourage you to access and review all of the important information contained in the proxy materials before voting. Under United States Securities and Exchange Commission rules, proxy materials do not have to be delivered in paper. Proxy materials can be distributed by making them available on the internet. If you want to receive a paper or e-mail copy of the proxy material, you must request one. There is no charge to you for requesting a copy. In order to receive a paper package in time for this year's meeting, you must make this request on or before May 12, 2025. SEE REVERSE FOR FULL AGENDA Internet: www.investorelections.com/EQ Call: Email: [email protected]* If requesting material by e-mail, please send a blank e-mail with the control number (located below) in the subject line. No other requests, instructions OR other inquiries should be included with your e-mail requesting material. 1-866-648-8133 Your control number Have the control number located in the box above available when you access the website and follow the instructions. Copyright © 2025 BetaNXT, Inc. or its affiliates. All Rights Reserved

Equillium, Inc. Annual Meeting of Stockholders Equillium THE BOARD OF DIRECTORS RECOMMENDS A VOTE: FOR all the nominees for director listed below and FOR Proposals 2, 3 and 4. PROPOSAL 1. To elect the Board's three nominees for Class I director named as nominees to hold office until the 2028 Annual Meeting of Stockholders and their successors are duly elected and qualified, or until their earlier death, resignation or removal. 1.01 Stephen Connelly, Ph.D. 1.02 Bala S. Manian, Ph.D. 1.03 Barbara Troupin, M.D. 2. To approve an amendment to our Amended and Restated Certificate of Incorporation to effect a reverse stock split of our common stock at a ratio in the range of 1-for-2 to 1-for-20, inclusive, with such ratio to be determined in the discretion of our Board of Directors and with such reverse stock split to be effected at such time and date, if at all, as determined by our Board of Directors in its sole discretion. 3. To ratify the appointment by the Audit Committee of the Board of KPMG LLP as the Company's independent registered public accounting firm for the fiscal year ending December 31, 2025. 4. To approve an amendment to our 2018 Equity Incentive Plan. NOTE: To conduct any other business properly brought before the Annual Meeting or any continuation, postponement or adjournment thereof.