An open-label, multi-center, phase I study to evaluate the safety/tolerability and pharmacokinetics of GFS202A in advanced solid tumor patients with pre-cachexia or cachexia. The primary objective is to assess the safety/tolerability of GFS202A, determine its maximum tolerated dose (MTD), and recommend a dose range for future studies.

Enroll participants with cancer cachexia or precachexia to receive GFS202A monotherapy. During the study period, participants will undergo assessments for safety and preliminary efficacy according to the visit schedule. Pharmacokinetic, anti-drug antibody (ADA), and pharmacodynamic (PD) /biomarker samples will be collected.

Inclusion Criteria:

1. Voluntarily participate in the study and sign the informed consent form.
2. Men or women between the ages of 18 and 80 years at the time of written informed consent.
3. Patients with histologically or cytologically confirmed solid tumors. Pre-cachectic and cachectic patients with weight loss or baseline BMI < 21 kg/m2 within 6 months before the first study dose.
4. Persistent concomitant appetite/eating problems related to cancer.
5. It has adequate organ function.
6. The ECOG PS score was 0-2.
7. The investigator judged the expected survival time to be ≥ 3 months.

Exclusion Criteria:

1. With active brain metastases.
2. With other active diseases that lead to reduced food intake or seriously affect digestion and absorption
3. Baseline BMI > 28 kg/m2.
4. With infectious diseases.
5. With clinically significant cardiovascular disease.
6. With uncontrolled metabolic diseases.
7. With known clinically significant allergic reactions to antibodies and excipients.
8. With history of drug or alcohol abuse.
9. Pregnant or lactating female subjects or women planning to become pregnant during the study.
10. With pleural, peritoneal, or pericardial effusion that causes overt symptoms or requires repeated drainage (frequency ≥ 1 time/month).
11. Use of any investigational drug within 28 days before the first study dose or within five half-lives of the drug, whichever was shorter, or planned for the duration of the study.