Partnerships	6 Months Ended
Jun. 30, 2025
Collaboration And License Agreement [Abstract]
Partnerships	7. Partnerships Asset Purchase Agreement with Ono Pharmaceutical Co., Ltd. On December 5, 2022, the Company and Ono, a Japan kabushiki kaisha, entered into an Asset Purchase Agreement pursuant to which the Company granted Ono the exclusive right, but not the obligation, to acquire the Company’s rights to itolizumab (the Option). These rights included all therapeutic indications and the rights to commercialize itolizumab in the United States, Canada, Australia, and New Zealand. In exchange for the Option, Ono paid the Company a one-time, upfront payment of an amount equal to JPY 3.5 billion, or $26.4 million. The Company was responsible for conducting all research and development of itolizumab, which had been funded by Ono from July 1, 2022 through October 30, 2024, the end of the option period. On October 30, 2024, the option period expired and the Asset Purchase Agreement automatically terminated pursuant to its terms. During the three and six months ended June 30, 2025, there was no revenue recognized under the Asset Purchase Agreement. During the three and six months ended June 30, 2024, the Company recognized revenue of $13.9 and $24.5 million, respectively, under the Asset Purchase Agreement. Such revenue was comprised of $9.2 million and $17.2 million associated with development funding for the three and six months ended June 30, 2024, respectively, and $4.7 million and $7.3 million associated with the amortization of the upfront payment for the three and six months ended June 30, 2024, respectively. Biocon Collaboration and License Agreement In May 2017, the Company entered into a collaboration and license agreement (which was amended in September 2018, April 2019, December 2019, April 2021 and November 2022), clinical supply agreement, investor rights agreement, and common stock purchase agreement (collectively License Agreements) with Biocon SA (subsequently assigned to Biocon Limited, or together, Biocon). Pursuant to the License Agreements, Biocon granted the Company an exclusive license to develop, make, have made, use, sell, have sold, offer for sale, import and otherwise exploit itolizumab and any pharmaceutical composition or preparation containing or comprising itolizumab that uses Biocon technology or Biocon know-how (collectively a Biocon Product) in the United States, Canada, Australia and New Zealand (collectively Equillium Territory). The Company also has the right to sublicense through multiple tiers to third parties, provided such sublicenses comply with the terms of the License Agreements and the Company provides Biocon a copy of each sublicense agreement within 30 days of execution. If the Company grants a third party a sublicense of its rights to develop and commercialize Biocon Products in Australia or New Zealand, the Company will be required to pay Biocon a high double-digit percentage of any upfront payment the Company receives from such sublicensee for such sublicense, as well as a high double-digit percentage of any additional payments the Company receives from such sublicensee for such sublicense, including but not limited to royalty payments on net sales of Biocon Products by such sublicensee. Under the License Agreements, the Company granted back to Biocon a license to use its technology and know-how related to itolizumab and Biocon Products in certain countries outside of the Equillium Territory. Pursuant to the License Agreements, Biocon agreed to be the Company’s exclusive supplier of itolizumab clinical drug product. Biocon will provide clinical drug product at no cost for up to three concurrent orphan indications until the Company’s first U.S. regulatory approval and all other clinical drug product at Biocon’s cost. In consideration of the rights granted to the Company by Biocon, the Company issued Biocon a total of 2,316,134 shares of its common stock. In addition, the Company is obligated to pay Biocon up to an aggregate of $30 million in regulatory milestone payments upon the achievement of certain regulatory approvals and up to an aggregate of $565 million in sales milestone payments upon the achievement of first commercial sale of product and specified levels of product sales. The Company is also required to pay royalties on tiers of aggregate annual net sales of Biocon Products by the Company, the Company’s affiliates and the Company’s sublicensees in the United States and Canada at percentages from the mid-single digits to sub-teen double-digits and on tiers of aggregate annual net sales of Biocon Products by the Company and the Company’s affiliates (but not the Company’s sublicensees) in Australia and New Zealand, in each case, subject to adjustments in certain circumstances. Biocon is also required to pay the Company royalties at comparable percentages for sales of itolizumab (EQ001) outside of the Equillium Territory if the approvals in such geographies included or referenced the Company’s data including data from certain of the Company’s clinical studies, subject to adjustments in certain circumstances. Under the License Agreements, net sales are calculated on a country-by-country basis and are subject to adjustments, including whether the Biocon Product is sold in the form of a combination product. As of June 30, 2025, the Company has not made or received payments in connection with the milestones or royalties within the agreement.

Partnerships

6 Months Ended

Jun. 30, 2025

Collaboration And License Agreement [Abstract]

7. Partnerships

Asset Purchase Agreement with Ono Pharmaceutical Co., Ltd.

On December 5, 2022, the Company and Ono, a Japan kabushiki kaisha, entered into an Asset Purchase Agreement pursuant to which the Company granted Ono the exclusive right, but not the obligation, to acquire the Company’s rights to itolizumab (the Option). These rights included all therapeutic indications and the rights to commercialize itolizumab in the United States, Canada, Australia, and New Zealand. In exchange for the Option, Ono paid the Company a one-time, upfront payment of an amount equal to JPY 3.5 billion, or $26.4 million.

The Company was responsible for conducting all research and development of itolizumab, which had been funded by Ono from July 1, 2022 through October 30, 2024, the end of the option period. On October 30, 2024, the option period expired and the Asset Purchase Agreement automatically terminated pursuant to its terms.

During the three and six months ended June 30, 2025, there was no revenue recognized under the Asset Purchase Agreement. During the three and six months ended June 30, 2024, the Company recognized revenue of $13.9 and $24.5 million, respectively, under the Asset Purchase Agreement. Such revenue was comprised of $9.2 million and $17.2 million associated with development funding for the three and six months ended June 30, 2024, respectively, and $4.7 million and $7.3 million associated with the amortization of the upfront payment for the three and six months ended June 30, 2024, respectively.

Biocon Collaboration and License Agreement

In May 2017, the Company entered into a collaboration and license agreement (which was amended in September 2018, April 2019, December 2019, April 2021 and November 2022), clinical supply agreement, investor rights agreement, and common stock purchase agreement (collectively License Agreements) with Biocon SA (subsequently assigned to Biocon Limited, or together, Biocon). Pursuant to the License Agreements, Biocon granted the Company an exclusive license to develop, make, have made, use, sell, have sold, offer for sale, import and otherwise exploit itolizumab and any pharmaceutical composition or preparation containing or comprising itolizumab that uses Biocon technology or Biocon know-how (collectively a Biocon Product) in the United States, Canada, Australia and New Zealand (collectively Equillium Territory). The Company also has the right to sublicense through multiple tiers to third parties, provided such sublicenses comply with the terms of the License Agreements and the Company provides Biocon a copy of each sublicense agreement within 30 days of execution. If the Company grants a third party a sublicense of its rights to develop and commercialize Biocon Products in Australia or New Zealand, the Company will be required to pay Biocon a high double-digit percentage of any upfront payment the Company receives from such sublicensee for such sublicense, as well as a high double-digit

percentage of any additional payments the Company receives from such sublicensee for such sublicense, including but not limited to royalty payments on net sales of Biocon Products by such sublicensee. Under the License Agreements, the Company granted back to Biocon a license to use its technology and know-how related to itolizumab and Biocon Products in certain countries outside of the Equillium Territory. Pursuant to the License Agreements, Biocon agreed to be the Company’s exclusive supplier of itolizumab clinical drug product. Biocon will provide clinical drug product at no cost for up to three concurrent orphan indications until the Company’s first U.S. regulatory approval and all other clinical drug product at Biocon’s cost.

In consideration of the rights granted to the Company by Biocon, the Company issued Biocon a total of 2,316,134 shares of its common stock.

In addition, the Company is obligated to pay Biocon up to an aggregate of $30 million in regulatory milestone payments upon the achievement of certain regulatory approvals and up to an aggregate of $565 million in sales milestone payments upon the achievement of first commercial sale of product and specified levels of product sales. The Company is also required to pay royalties on tiers of aggregate annual net sales of Biocon Products by the Company, the Company’s affiliates and the Company’s sublicensees in the United States and Canada at percentages from the mid-single digits to sub-teen double-digits and on tiers of aggregate annual net sales of Biocon Products by the Company and the Company’s affiliates (but not the Company’s sublicensees) in Australia and New Zealand, in each case, subject to adjustments in certain circumstances. Biocon is also required to pay the Company royalties at comparable percentages for sales of itolizumab (EQ001) outside of the Equillium Territory if the approvals in such geographies included or referenced the Company’s data including data from certain of the Company’s clinical studies, subject to adjustments in certain circumstances. Under the License Agreements, net sales are calculated on a country-by-country basis and are subject to adjustments, including whether the Biocon Product is sold in the form of a combination product. As of June 30, 2025, the Company has not made or received payments in connection with the milestones or royalties within the agreement.