Exhibit 99.1 Immatics Announces Full Year 2023 Financial Results and Corporate Update · Interim clinical data update on ACTengine IMA203 GEN1 (PRAME) in melanoma at RP2D in November 2023: 50% confirmed objective response rate with median duration of response not reached at median follow-up of 14.4 months; IMA203 was well tolerated · Registration-enabling randomized Phase 2/3 trial for ACTengine IMA203 GEN1 in 2L+ melanoma planned to begin in 2024 · Next data update on IMA203 GEN1 and IMA203CD8 GEN2 planned ...