Exhibit 99.1 Arcus Biosciences Reports Fourth-Quarter and Full-Year 2023 Financial Results and Provides a Pipeline Update • Arcus and Gilead announced an additional equity investment of $320 million into Arcus and modifications to their domvanalimab + zimberelimab clinical program to focus on the highest unmet medical needs and largest market opportunities • Pharmacokinetic (PK), pharmacodynamic (PD), safety and early efficacy data, including initial observations from the expansion cohort, from ARC-20, supp ...