Inclusion Criteria:

Ia phase:

1. Male and female subjects aged 18-55 years (inclusive), at the time of signing the ICF.;
2. Body weight ≥ 50 kg for males and ≥ 45 kg for females, with a body mass index (BMI = weight (kg)/height 2 (m) 2) of 18.5-26 kg/m2 (inclusive);
3. Participants (including their partners) who have no plan to become pregnant and voluntarily use effective contraception from screening to 6 months after the last dose;

Ib phase:

1. Subjects aged ≥ 18 years at screening;
2. Subjects who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, and other study procedures;
3. ECOG performance status score of 0, 1;
4. Cancer cachexia documented in medical records; -

Exclusion Criteria:

Ia phase:

1. Subjects with clinically significant abnormal laboratory findings, or with clinically significant diseases or conditions, who are considered by the investigator to be ineligible for enrollment in this study.
2. History of HIV infection, syphilis, hepatitis B, or hepatitis C;
3. History of recurrent infections or active infections；
4. Subjects who, in the judgment of the investigator, are not suitable for participation in the study.

Ib phase:

1. Current active reversible causes of decreased food intake
2. Cachexia caused by other reasons
3. Receiving tube feedings or parenteral nutrition within 28 days prior to the first administration of the investigational product
4. Presence of concomitant conditions, other than neoplastic cachexia, which are deemed by the investigator to cause difficulty in oral intake or malabsorption of ingested food.
5. Subjects with known allergy to QLS2319 or any of its components, or with a history of severe allergic reactions or uncontrolled allergic asthma.