This study is an open-label, multicenter Phase I/II clinical trial to evaluate the safety, tolerability, pharmacokinetics and efficacy of SHR-1681 for injection in patients with advanced solid tumors.

Inclusion Criteria:

1. Subjects must voluntarily agree to participate in the trial and sign a written informed consent form;
2. Subjects with histologically or cytologically confirmed unresectable locally advanced or metastatic solid tumors which is relapsed or refractory to standard treatment, or lack of standard treatment, or standard treatment is not applicable currently;
3. Have at least one measurable tumor lesion per RECIST v1.1;
4. ECOG performance score of 0-1;
5. Life expectancy ≥ 3 months;
6. Adequate bone marrow and organ function.

Exclusion Criteria:

1. Subjects with active central nervous system metastases or meningeal metastases;
2. History of serious cardiovascular and cerebrovascular diseases;
3. Subjects with a history of interstitial pneumonitis or imaging at screening suggestive of suspected interstitial pneumonitis;
4. Severe infection within 4 weeks prior to the first dose;
5. Ongoing or previous anti-tumor therapies within 4 weeks prior to the first dose of study drug;
6. Adverse reactions of previous anti-tumor treatment have not recovered to Grade ≤ 1 per NCI-CTCAE v5.0.