This is a multicenter, open-label, Phase I clinical study to evaluate the safety, tolerability, pharmacokinetics, and efficacy of SNH-118110 administered orally. The study consists of a dose-escalation phase and a dose-expansion phase.

This first-in-human, open-label, multicenter Phase I study is designed to assess the safety, tolerability, pharmacokinetics (PK), and preliminary efficacy of SNH-118110 administered orally. The study comprises two sequential parts: a dose-escalation phase to identify the maximum tolerated dose (MTD) or maximum administered dose (MAD), followed by a dose-expansion phase to further evaluate safety and anti-tumor activity. The primary endpoints include safety, MTD, and/or MAD.

Inclusion Criteria:

• Ability to understand and voluntarily sign an informed consent form (ICF) prior to any study related procedures.
• Age ≥ 18 years at the time of signing the ICF.
• Histologically or cytologically confirmed diagnosis of advanced solid tumors, with the following additional requirements:

Dose-escalation phase: Patients with advanced solid tumors harboring a RET gene alteration who have failed standard therapy or are intolerant to standard therapy.

Dose-expansion phase:

Cohort 1: Locally advanced or metastatic NSCLC with RET gene fusion who have progressed after at least one prior line of therapy, which must include a RET inhibitor.

Cohort 2: Treatment-naïve patients with locally advanced or metastatic NSCLC harboring a RET gene fusion.

Cohort 3: Other advanced solid tumors harboring RET gene alterations.

• At least one measurable target lesion according to RECIST version 1.1.
• Documentation of a RET fusion or other activating RET gene alteration (based on a local or central laboratory report).
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, with no deterioration within the 2 weeks prior to the first dose of study drug.
• Life expectancy of at least 3 months.

Exclusion Criteria:

• Presence of other known oncogenic driver mutations.
• Prior anti-tumor therapy within specified washout periods prior to first dose (e.g., small molecules, biologics, radiotherapy, major surgery), or failure to recover from clinically significant toxicities.
• Clinically significant uncontrolled or active conditions, including but not limited to:

Inadequate bone marrow, hepatic, or renal function. Significant cardiovascular disease (e.g., uncontrolled hypertension, prolonged QTc, poor ejection fraction, recent thromboembolic events).

Active or uncontrolled infections, bleeding diathesis, or significant pleural/abdominal/pericardial effusion requiring intervention.

Central nervous system metastases unless stable and asymptomatic off steroids.

• Conditions affecting oral drug absorption or gastrointestinal function.
• History of severe allergic reactions to similar agents.
• Pregnant or lactating women, or patients with serious concurrent medical or psychiatric conditions that would compromise safety or study compliance.