This study is a Phase I/IIa, multi-center, open-label study of BR790 in combination with Tislelizumab with a dose escalation part followed by a dose expansion part in adult subjects with advanced solid tumors.

These treatment to characterize the safety, tolerability, PK, PD and preliminary antitumor activity.

The study treatment will be administered until the subject experiences unacceptable toxicity, progressive disease, and/or has treatment discontinued at the discretion of the Investigator or the subject, or due to withdrawal of consent.

Phase 1 (Dose Escalation Phase of BR790 Tablets Combined with Tislelizumab Injection): According to the incidence of DLT in BR790 Tablets Combined with Tislelizumab Injection Monoclonal Antibody in the Treatment of Advanced Solid Tumors, MTD and the Phase 2 clinical trial dose (RP2D) combining PK , efficacy and safety data were determined.

Stage II (BR790 Tablets combined with tislelizumab injection dose expansion stage): Evaluate the objective response rate (ORR) of BR790 Tablets combined with tislelizumab injection according to Response Evaluation Criteria in Solid Tumors (RECIST) V1.1 .

Inclusion Criteria:

1. Sign informed consent voluntarily.
2. Age ≥18 and ≤75 years old.
3. Subjects with advanced solid tumors diagnosed by histology or cytology，whose desease progressed after standard treatment or have no standard treatment.
4. Had at least one measurable lesion.
5. ECOG≤1.
6. Expected survival period ≥ 3 months.

Exclusion Criteria:

1. Any previous treatment with SHP-2 inhibitor.
2. Symptomatic brain metastases.
3. Subjects with thoracic/ascites fluid that need drainage or intervention.
4. Subjects with not enough organ functional reserve at baseline, which met at least one of the following criteria： ANC<1.5×10^9/L PLT<100×10^9/L Hb<90g/L TBIL>1.5×ULN ALT, AST>2.5×ULN (without liver metastases) or ALT, AST>5×ULN (with liver metastases), Cr >1.5×ULN.
5. With uncontrolled severe disease.