X0202 SCHEDULE 13G/A 0001072613-22-000148 0001666306 XXXXXXXX LIVE 4 Common Stock par value $0.0001 per share 03/31/2026 0001806952 Lyell Immunopharma, Inc. 55083R203 201 Haskins Way South San Francisco CA 94080 Rule 13d-1(d) ARCH Venture Fund IX, L.P. DE 0 3247162 0 3247162 3247162 N 13.9 PN ARCH Venture Fund IX Overage, L.P. DE 0 3247162 0 3247162 3247162 N 13.9 PN ARCH Venture Fund XIII, L.P. DE 0 3247162 0 3247162 3247162 N 13.9 PN ARCH Venture Partners IX, L.P. DE 0 3247162 0 3247162 3247162 N 13.9 PN ARCH Venture Partners IX Overage, L.P. DE 0 3247162 0 3247162 3247162 N 13.9 PN ARCH Venture Partners IX, LLC DE 0 3247162 0 3247162 3247162 N 13.9 OO ARCH Venture Partners XIII, L.P. DE 0 3247162 0 3247162 3247162 N 13.9 PN ARCH Venture Partners XIII, LLC DE 0 3247162 0 3247162 3247162 N 13.9 OO Keith Crandell X1 0 3247162 0 3247162 3247162 N 13.9 IN Clinton Bybee X1 0 1820634 0 1820634 1820634 N 7.8 IN Robert Nelsen X1 0 3247162 0 3247162 3247162 N 13.9 IN Kristina Burow X1 0 3247162 0 3247162 3247162 N 13.9 IN Steven Gillis X1 0 3247162 0 3247162 3247162 N 13.9 IN Paul Berns X1 0 1426528 0 1426528 1426528 N 6.1 IN Lyell Immunopharma, Inc. 201 Haskins Way, South San Francisco, CA 94080 ARCH Venture Fund IX, L.P. ("AVF IX"); ARCH Venture Partners IX, L.P. ("AVP IX LP"); ARCH Venture Partners IX, LLC ("AVP IX LLC"); ARCH Venture Fund IX Overage, L.P. ("AVF IX Overage"); ARCH Venture Partners IX Overage, L.P. ("AVF IX Overage GP"); ARCH Venture Fund XIII, L.P. ("AVF XIII"); ARCH Venture Partners XIII, L.P. ("AVP XIII LP"); ARCH Venture Partners XIII, LLC ("AVP XIII LLC") (collectively, the "Reporting Entities" and individually, each a "Reporting Entity"); and Keith Crandell ("Crandell"), Robert Nelsen ("Nelsen") and Clinton Bybee ("Bybee") (collectively, the "IX Managing Directors" and individually, each a "IX Managing Director"), Steven Gillis ("Gillis") and Kristina Burow ("Burow"), along with Nelsen and Crandell, collectively the "IX Investment Committee" and individually "IX Committee Members"; and Paul Berns ("Berns"), along with Nelsen, Crandell, Gillis, and Burow, collectively the "XIII Investment Committee" and individually "XIII Committee Members". The Reporting Entities, IX Managing Directors, IX Committee Members, and XIII Committee Members collectively are referred to as the "Reporting Persons". The Reporting Persons are filing this report with respect to shares of Common Stock, par value $0.0001 per share (the "Common Stock") of Lyell Immunopharma, Inc. (the "Issuer"). 8755 W. Higgins Avenue, Suite 1025, Chicago, IL 60631 Each of AVF IX, AVF IX LP, AVF IX Overage, AVF IX Overage GP, AVF XIII and AVF XIII LP are limited partnerships organized under the laws of the State of Delaware. AVP IX LLC and AVP XIII LLC are each a limited liability company organized under the laws of the State of Delaware. Each Managing Director is a US citizen. Y AVF IX is the record owner of 910,317 shares of Common Stock (the "AVF IX Shares") as of March 31, 2026. AVP IX LP, as the sole general partner of AVF IX, may be deemed to beneficially own the AVF IX Shares. AVF IX Overage is the record owner of 910,317 shares of Common Stock (the "AVF IX Overage Shares") as of March 31, 2026. AVF IX Overage GP, as the sole general partner of AVF IX Overage, may be deemed to beneficially own the AVF IX Overage Shares, combined with AVF IX Shares (the "IX Record Shares"). AVF XIII is the record owner of 1,426,528 shares of Common Stock (the "XIII Record Shares") as of March 31, 2026. AVP XIII LP, as the sole general partner of AVF XIII, may be deemed to beneficially own the XIII Record Shares. AVP IX LLC, as the sole general partner of AVP IX LP and AVF IX Overage GP, may be deemed to beneficially own the IX Record Shares. As managing directors and investment committee members of AVP IX LLC, each IX Managing Director and IX Committee Members may also be deemed to share the power to direct the disposition and vote of the IX Record Shares. AVP XIII LLC, as the sole general partner of AVP XIII LP, may be deemed to beneficially own the XIII Record Shares. As investment committee members of AVP XIII LLC, XIII Committee Members may also be deemed to share the power to direct the disposition and vote of the XIII Record Shares. The information required by Item 4(b) is incorporated by reference to Row 11 of the cover pages hereto. The percentages set forth on the cover sheet for each Reporting Person is based upon 23,334,087 shares of Common Stock outstanding as of May 1, 2026, as reported on the Issuer's Quarterly Report on Form 10-Q as filed with the Securities and Exchange Commission on May 6, 2026. Each Reporting Person disclaims beneficial ownership of such shares of Common Stock except for the shares, if any, such Reporting Person holds of record. See row 11 of the cover pages. See row 5 of the cover pages. See row 6 of the cover pages. See row 7 of the cover pages. See row 8 of the cover pages. Y Y Y Y Y Y ARCH Venture Fund IX, L.P. /s/ ARCH Venture Partners IX, L.P. 05/15/2026 ARCH Venture Partners IX, LLC 05/15/2026 /s/ Mark McDonnell 05/15/2026 ARCH Venture Fund IX Overage, L.P. /s/ ARCH Venture Partners IX Overage, L.P. 05/15/2026 /s/ ARCH Venture Partners IX, LLC 05/15/2026 /s/ Mark McDonnell 05/15/2026 ARCH Venture Fund XIII, L.P. /s/ ARCH Venture Partners XIII, L.P. 05/15/2026 /s/ ARCH Venture Partners XII, LLC 05/15/2026 /s/ Mark McDonnell 05/15/2026 ARCH Venture Partners IX, L.P. /s/ ARCH Venture Partners IX, LLC 05/15/2026 /s/ Mark McDonnell 05/15/2026 ARCH Venture Partners IX Overage, L.P. /s/ ARCH Venture Partners IX, LLC 05/15/2026 /s/ Mark McDonnell 05/15/2026 ARCH Venture Partners IX, LLC /s/ Mark McDonnell 05/15/2026 ARCH Venture Partners XIII, L.P. /s/ ARCH Venture Partners XIII, LLC 05/15/2026 /s/ Mark McDonnell 05/15/2026 ARCH Venture Partners XIII, LLC /s/ Mark McDonnell 05/15/2026 Keith Crandell /s/ Mark McDonnell 05/15/2026 Clinton Bybee /s/ Mark McDonnell 05/15/2026 Robert Nelsen /s/ Mark McDonnell 05/15/2026 Kristina Burow /s/ Mark McDonnell 05/15/2026 Steven Gillis /s/ Mark McDonnell 05/15/2026 Paul Berns /s/ Mark McDonnell 05/15/2026 * This Schedule 13G was executed by Mark McDonnell pursuant to a Power of Attorney filed as Exhibit 24 to the Form 3 relating to the beneficial ownership of shares of Gossamer Bio, Inc. by the Reporting Persons filed with the Securities Exchange Commission on February 7, 2019 and incorporated herein in its entirety by reference.