This open label ascending dose study is designed to evaluate the safety, pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity of AV-380 in cancer patients with Cachexia. AV-380 is an immunoglobulin (Ig) G1 monoclonal antibody (mAb) intended to bind circulating human growth differentiation factor 15 (GDF-15), a cytokine involved in cancer-induced cachexia.

Inclusion Criteria:

1. Patient must be ≥ 18 years of age at the time of signing the informed consent.

2. Patients with histologically confirmed solid tumor cancer who are actively receiving SoC therapy for this cancer.

3. Patients with cachexia as defined by Fearon criteria:

   1. Weight loss > 5% over past 6 months (in absence of simple starvation), or
   2. BMI < 20 kg/m2 and any degree of weight loss > 2%, or
   3. Sarcopenia and any degree of weight loss > 2%

4. Patients with life expectancy ≥ 3 months

Exclusion Criteria:

1. History of allergic or anaphylactic reaction to any monoclonal antibody (IgG protein) or molecules made of components of monoclonal antibody
2. Known brain metastases or cranial epidural disease unless adequately treated with radiotherapy and/or surgery (including radiosurgery) and stable for at least 2 weeks before first dose of study treatment.
3. Myocardial infarction or heart failure of New York Heart Association Grade 3-4 within 3 months prior to start of protocol therapy
4. Uncontrolled pericardial effusion, or ascites requiring recurrent drainage procedures (once monthly or more frequently)
5. Cachexia is caused by other reasons (e.g., severe chronic obstructive pulmonary disease, heart failure, or HIV/AIDS), or the patient has uncontrolled reversible causes of reduced oral food intake, including, but not limited to, oral mucositis, nausea/vomiting, diarrhea, and/or obstruction, impairing the patient's ability to eat as determined by the Investigator.
6. Patients receiving tube feedings or parenteral nutrition at the time of Screening.