Background: IDO is an enzyme of interest in immuno-oncology because of the immunosuppressive effects that result from its role in tryptophan catabolism. Clinical trials of IDO inhibitors with immunotherapy are under active investigation. The addition of angiogenesis inhibitor may further enhance the anti-tumor immune responses. Here we report the safety and efficacy results of SHR9146 (IDO inhibitor) plus camrelizumab (PD-1 antibody) with/without apatinib (VEGFR-2 inhibitor) in patients (pts) with advanced solid cancers who failed standard antitumor therapies. Methods: This was an open-label, phase I study. Eligible puts would receive SHR9146 (escalated dose) plus camrelizumab (200 mg IV, q2w) alone (Cohort A) or in combination with apatinib (250 mg p.o. qd) (Cohort B). Each cohort was conducted according to a 3+3 dose escalation design. The starting dose of SHR9146 was 100mg bid, followed by 200, 400, 600 mg bid. The two primary endpoints were Dose-limiting Toxicity (DLT) and Maximum Tolerated Dose (MDT). The secondary objective was to analysis the incidence of Adverse Events (AEs) and efficacy. Results: As of Oct 31, 2020, 23 pts have been enrolled (Cohort A:14, Cohort B: 9; median age: 54 years; median prior therapies: 2 lines;). Cohort A was escalating at 600mg, and Cohort B was escalating at 400mg. Two pts experienced DLTs: one DLT (G4 hypercalcemia) was observed at 600mg in Cohort A; the other DLT (G3 rash) was observed at 400mg in Cohort B. MDT was not reached and the study was still ongoing. In Cohort A, ORR and DCR in evaluable pts were 21.4% (3/14, all confirmed) and 42.9% (6/14). Partial response was observed in 3 pts with liver cancer (1/3), renal cancer (1/3), and cervix cancer (1/3). In Cohort B, ORR and DCR in evaluable pts were 33.3%(3/9, all confirmed) and 77.8%(7/9). Partial response was observed in 3 pts with SCLC (1/3), prostate cancer (1/3) and renal cancer (1/3). The incidence of pts with TRAEs and grade>=3 TRAEs were 91.3% (21/23) and 39.1% (9/23) respectively. The most common grade>=3 TRAEs were hypercalcemia (26.1%, 6/23), fatigue (17.4%, 4/23) and nausea (13.0%, 3/23). No fatal AEs were observed. G3 nausea, G3 lipase increased and G2 GGT increased resulted in SHR9146 dose reduction in 3 pts (Cohort A). Conclusions: SHR9146 plus camrelizumab in combination with/without apatinib demonstrated promising anti-tumor activity with acceptable safety in pts with advanced solid tumors. Further study is needed to validate the efficacy and safety. Clinical trial information: NCT03491631