The investigational drug, SOA101, is a nanobody-based trispecific antibody T cell engager targeting PD-L1/HLA-G/CD3. This is a Phase I/IIa study including dose-escalation, dose optimization and dose expansion parts to exam safety, tolerability, pharmacokinetics, immunogenecity and efficacy of SOA101 on advanced or metastatic solid tumor treatment.

Inclusion Criteria:

1. Male or female subjects aged ≥ 18 years old.

2. Subjects with locally advanced, or metastatic solid tumors confirmed histologically or cytologically as one of the following cancer types for whom no suitable alternative standard-of-care therapy exists:

   1. Non-small cell lung cancer (NSCLC);
   2. Ovarian cancer (OC);
   3. Head and neck carcinoma (H&N);
   4. Breast cancer (BC);
   5. Colorectal cancer (CRC).

3. Pathologically confirmed combined positive score (CPS) with ≥ 1% expression of PD-L1.

4. At least one measurable lesion

5. Adequate organ function

6. Female subject must either not be of childbearing potential or a negative pregnancy test

7. Non-vasectomized male subjects must practice highly effective contraception

Exclusion Criteria:

1. Active bacterial, fungal, viral OR atypical infection requiring systemic medication.
2. Received any investigational drug within 4 weeks before screening.
3. Confirmed active HIV (without controlled disease on HAART), HBV, or HCV infection.
4. Symptomatic, unstable central nervous system malignancy OR metastasis
5. Have received organ or tissue transplantation or allogeneic cell therapies.
6. Non-adequate cardiac function
7. Known hypersensitivity to any anti-PD-L1 therapy or anti-CD3 therapy.