Exhibit 99.1 Lyell Immunopharma Reports Business Highlights and Financial Results for the First Quarter 2024 • Expect to share initial clinical and translational data from the Phase 1 trial of LYL797, a ROR1-targeted CAR T‑cell product candidate, this quarter • On track to report initial clinical data from the Phase 1 trial of LYL845, an epigenetically enhanced TIL product candidate, in the second half of 2024 • IND for second generation ROR1-targeted CAR T-cell product candidate on track for submission thi ...