Exhibit 5.1
August 14, 2020
Equillium, Inc.
2223 Avenida de la Playa, Suite 105
La Jolla, CA 92037
Re: Equillium, Inc.
Ladies and Gentlemen:
You have
requested our opinion with respect to certain matters in connection with the offer and sale by Equillium, Inc., a Delaware corporation (the “Company”), of 5,750,000 shares (the “Shares”) of the Company’s common stock par
value $0.0001 per share (the “Common Stock”), which amount includes 750,000 shares of Common Stock that may be issued and sold by the Company to the underwriters pursuant to their option to purchase additional shares, pursuant to an
underwriting agreement dated August 13, 2020 with Jefferies LLC, SVB Leerink LLC and Stifel, Nicolaus & Company, Incorporated acting as representatives of the several underwriters named on Schedule A thereto (the
“Underwriting Agreement”).
The Shares will be issued pursuant to (i) the Company’s registration statement on Form S-3 (File No. 333-234683) declared effective by the Securities and Exchange Commission on November 25, 2019 under the Securities Act of 1933, as amended (the
“Securities Act”) and the prospectus dated November 25, 2019 included in such registration statement (the “Registration Statement”), and (ii) a preliminary prospectus supplement dated August 13, 2020 and a final
prospectus supplement dated August 13, 2020 and filed with the Securities and Exchange Commission on August 14, 2020 (collectively, the “Prospectus”).
We have examined the Registration Statement, the Prospectus, the Underwriting Agreement and other instruments, certificates, records and
documents, matters of fact and questions of law that we have deemed necessary for the purposes of this opinion.
In our examination of the
foregoing and in rendering the opinion set forth herein, we have assumed, without independent investigation or verification: (i) the genuineness of all signatures on all agreements, instruments, corporate records, certificates and other
documents submitted to us; (ii) the authenticity and completeness of all agreements, instruments, corporate records, certificates and other documents submitted to us as originals; (iii) that all agreements, instruments, corporate records,
certificates and other documents submitted to us as certified, electronic, facsimile, conformed, photostatic or other copies conform to authentic originals thereof, and that such originals are authentic and complete; (iv) the legal capacity and
authority of all persons or entities executing all agreements, instruments, corporate records, certificates and other documents submitted to us; (v) the due authorization, execution and delivery of all agreements, instruments, certificates and
other documents by all parties thereto; (vi) that the statements contained in the certificates and comparable documents of public officials, officers and representatives of the Company and other persons on which we have relied for the purposes
of this opinion letter are true and correct; and (vii) that the officers and directors of the Company have properly exercised their fiduciary duties. As to all questions of fact material to the opinion set forth herein and as to the materiality
of any fact or other matter referred to herein, we have relied (without independent investigation) upon representations and certificates or comparable documents of officers and representatives of the Company.
Based upon the foregoing, we are of the opinion that the Shares have been duly authorized by all necessary corporate action on the part of the
Company and, when issued in accordance with the terms of the Underwriting Agreement and the Registration Statement, the Shares will be validly issued, fully paid and nonassessable.
