X0202 SCHEDULE 13G/A 0001104659-25-112816 0001940272 XXXXXXXX LIVE 1 Common Stock, par value $0.0001 per share 03/31/2026 0001746466 Equillium, Inc. 29446K106 2223 Avenida de la Playa Suite 105 La Jolla CA 92037 Rule 13d-1(b) ADAR1 Capital Management, LLC b TX 0.00 6603754.00 0.00 6603754.00 6603754.00 N 9.9 IA OO Includes (i) 2,786,136 shares of common stock, par value $0.0001 per share ("Common Stock") held by ADAR1 Partners, LP, (ii) 404,699 shares of Common Stock held by Spearhead Insurance Solutions IDF, LLC, (iii) 533,742 shares of Common Stock held by ADAR1 SPV I, LP, (iv) 2,082 shares of Common Stock held by other separately managed accounts and (v) 2,877,095 shares of Common Stock underlying prefunded warrants held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC as of March 31, 2026. Excludes 557,415 shares of Common Stock underlying prefunded warrants held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC, the exchange and exercise of which are subject to 9.99% beneficial ownership limitations. As the investment manager of ADAR1 Partners, LP and ADAR1 SPV I, LP and as the sub-advisor of Spearhead Insurance Solutions IDF, LLC and the separately managed accounts referenced above, ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP; Spearhead Insurance Solutions IDF, LLC; ADAR1 SPV I, LP and the separately managed accounts. Based on 63,226,556 shares of Common Stock of Equillium Inc. (the "Issuer") outstanding as of March 31, 2026, reported in the Issuer's Form 10Q for the quarterly period ended March 31, 2026, filed with the Securities and Exchange Commission on May 13, 2026. ADAR1 Capital Management GP, LLC b TX 0.00 6306184.00 0.00 6306184.00 6306184.00 N 9.5 OO Includes (i) 2,786,136 shares of common stock, par value $0.0001 per share ("Common Stock") held by ADAR1 Partners, LP, (ii) 533,742 shares of Common Stock held by ADAR1 SPV I, LP and (iii) 2,986,306 shares of Common Stock underlying prefunded warrants held by ADAR1 Partners, LP and ADAR1 SPV I, LP as of March 31, 2026. As the general partner of ADAR1 Partners, LP and ADAR1 SPV I, LP, ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP and ADAR1 SPV I, LP. Based on 63,226,556 shares of Common Stock of Equillium Inc. (the "Issuer") outstanding as of March 31, 2026, reported in the Issuer's Form 10Q for the quarterly period ended March 31, 2026, filed with the Securities and Exchange Commission on May 13, 2026. Daniel Schneeberger b V8 0.00 6603754.00 0.00 6603754.00 6603754.00 N 9.9 HC IN Includes (i) 2,786,136 shares of common stock, par value $0.0001 per share ("Common Stock") held by ADAR1 Partners, LP, (ii) 404,699 shares of Common Stock held by Spearhead Insurance Solutions IDF, LLC, (iii) 533,742 shares of Common Stock held by ADAR1 SPV I, LP, (iv) 2,082 shares of Common Stock held by other separately managed accounts and (v) 2,877,095 shares of Common Stock underlying prefunded warrants held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC as of March 31, 2026. Excludes 557,415 shares of Common Stock underlying prefunded warrants held by ADAR1 Partners, LP, ADAR1 SPV I, LP and Spearhead Insurance Solutions IDF, LLC, the exchange and exercise of which are subject to 9.99% beneficial ownership limitations. As the manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC, Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP; Spearhead Insurance Solutions IDF, LLC; ADAR1 SPV I, LP; and the separately managed accounts referenced above. Based on 63,226,556 shares of Common Stock of Equillium Inc. (the "Issuer") outstanding as of March 31, 2026, reported in the Issuer's Form 10Q for the quarterly period ended March 31, 2026, filed with the Securities and Exchange Commission on May 13, 2026. Equillium, Inc. 2223 Avenida de la Playa, Suite 105 La Jolla, CA 92037 This Schedule is being filed on behalf of each of the following persons (each, a "Reporting Person" and collectively, the "Reporting Persons"): (i) ADAR1 Capital Management, LLC ("ADAR1 Capital Management"); (ii) ADAR1 Capital Management GP, LLC ("ADAR1 General Partner"); and (iii) Daniel Schneeberger ("Mr. Schneeberger"). The address of the principal business office of each of the Reporting Persons is 3503 Wild Cherry Drive, Building 9, Austin, Texas 78738. (i) ADAR1 Capital Management is a Texas limited liability company; (ii) ADAR1 General Partner is a Texas limited liability company; and (iii) Mr. Schneeberger is a citizen of Switzerland. N IA HC The information contained on the cover pages of this Schedule 13G is incorporated herein by reference. The information contained on the cover pages of this Schedule 13G is incorporated herein by reference. The information contained on the cover pages of this Schedule 13G is incorporated herein by reference. The information contained on the cover pages of this Schedule 13G is incorporated herein by reference. The information contained on the cover pages of this Schedule 13G is incorporated herein by reference. The information contained on the cover pages of this Schedule 13G is incorporated herein by reference. Y Y N Mr. Schneeberger is filing this Schedule 13G as a control person in respect of shares beneficially owned by ADAR1 Capital Management, an investment adviser as described in SS 240.13d-1(b)(1)(ii)(E). Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. ADAR1 Capital Management, LLC /s/ Daniel Schneeberger 05/15/2026 ADAR1 Capital Management GP, LLC /s/ Daniel Schneeberger 05/15/2026 Daniel Schneeberger /s/ Daniel Schneeberger 05/15/2026