This study is to evaluate the safety, tolerability, PK, and preliminary efficacy of NTS071 in adults with TP53 Y220C-mutated solid tumors.

This is a Phase 1/2a, first-in-human, open-label, multi-center study with the aim of exploring the safety, tolerability, PK, and preliminary efficacy of NTS071 in subjects with unresectable locally advanced or metastatic solid tumors containing a TP53 Y220C mutation.

This study includes two parts: Phases 1 and 2a. The Phase 1 part consists of the dose escalation and backfill part; The Phase 2a part consists of the cohort expansion part.

Inclusion Criteria:

1. Male or female subjects, ≥ 18 years
2. Advanced solid tumors with TP53 Y220C mutation
3. Previously treated with one or more lines of anticancer therapy and progressive disease
4. At least one measurable lesion according to RECIST version 1.1 criteria
5. Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 or 1
6. Adequate organ and bone marrow function

Exclusion Criteria:

1. Known CNS primary tumor and active or untreated CNS metastases
2. History of another primary malignancy that has been diagnosed or required therapy within the past 2 years
3. Toxicities of prior therapy have not been resolved to ≤ Grade 1 or to baseline
4. Significant cardiovascular disease, including congestive heart failure
5. Known hepatitis B, hepatitis C, or human immunodeficiency virus infection that is active
6. Have a known psychiatric or substance abuse disorder that would interfere with the participant's ability to cooperate with the requirements of the study.