Initial Filing of Schedule 13G by RA Capital Management, L.P. and Affiliates for Equillium, Inc.

RA Capital Management, L.P. and its affiliates, including Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund, L.P., have filed a Schedule 13G indicating beneficial ownership of 6,480,209 shares of Equillium, Inc. common stock, representing 9.9% ownership. This filing is related to a recent private placement of equity securities that closed on March 13, 2026. The ownership percentage is capped at 9.9% due to a beneficial ownership blocker provision in pre-funded warrants, which prevents the exercise of warrants that would result in ownership exceeding this threshold. The reporting persons have disclaimed beneficial ownership for purposes other than Section 13(d) obligations. The filing confirms that the securities were not acquired or held to influence or change control of the issuer.