The goal of this clinical trial is to evaluate the safety, tolerability and pharmacokinetic characteristics of Singletine in healthy adult subjects. The main questions it aims to answer are: safety and tolerability of Singletine in healthy subjects, the pharmacokinetic characteristics after single and multiple doses and the effect of food on the pharmacokinetic characteristics. Participants will be treated with Singletine orally and safety and pharmacokinetic evaluations will be conducted according to the protocol.

This study will be an double-blinded, single-center phase I clinical trial. After being informed about the study and potential risks, all subjects giving written informed consent will undergo a 2-week screening period to determine eligibility for study entry. And then subjects will be administered for single-dose treatment or 7-day multiple-dose treatment and 9-day safety follow up after the last dose of treatment. The safety and pharmacokinetic measures will be conducted according to the protocol.

Inclusion Criteria:

• Age 18-45 years old (including both endpoints), healthy males or females;
• Male weight ≥50 kg, female weight ≥45 kg, body mass index (BMI) between 19-28 kg/m2 (including both endpoints);
• No significant abnormal clinical symptoms, normal physical examination, vital signs, 12-lead electrocardiogram (ECG), chest CT, ultrasound, and important indicators in laboratory tests show no clinically significant abnormalities;
• Subjects (including partners) have no parenting plans within 90 days from screening to the last administration of the study drug and voluntarily adopt appropriate and effective contraceptive measures (non-oral contraceptives);
• Have a full understanding of this study, voluntarily participate in the trial, and voluntarily sign the written informed consent form.

Exclusion Criteria:

• Pregnant or lactating women;
• Subjects with special dietary requirements who cannot adhere to a uniform diet;
• Subjects suspected or confirmed to be allergic to any component similar to the study drug or any ingredient in the study drug, or individuals with an allergic constitution;
• Subjects with past or present severe diseases/abnormalities (including but not limited to cardiac/cerebrovascular, respiratory, endocrine, metabolic, renal, hepatic, gastrointestinal, dermatologic, malignant tumors, hematological, immunological, rheumatic, neurological or psychiatric diseases), or any acute or chronic disease or physiological condition that could interfere with the trial results;
• Subjects with severe infectious diseases within six months prior to screening, or a history of herpes zoster, disseminated herpes zoster, any infectious history judged by the investigator to likely worsen due to participation in the study, or any infectious history requiring antimicrobial treatment within two weeks after screening; or the presence of active infections, including acute and chronic infections as well as localized infections;
• Subjects with active or latent tuberculosis, or with a history of tuberculosis.