To Evaluate Safety, Tolerability, PK/PD & Food Effect of Single/Multiple Oral TUL321 Capsules in Healthy Participants.

Prior treatment

• Suspected or confirmed allergy to investigational product or its similar components; or history of multiple drug/food allergies.
• Confirmed active systemic bacterial, viral or fungal infection within 2 weeks before screening.
• History of confirmed encapsulated bacterial infection within 6 months before screening, including but not limited to meningococcus, streptococcus pneumoniae, Haemophilus influenzae type b.
• Received other vaccines not specified in the protocol within 1 month before screening, or plan to receive such vaccines during the study.
• Participated in another interventional clinical trial within 3 months before screening (excluding subjects who only completed screening without enrollment, or enrolled but did not receive study treatment).
• Average daily cigarette consumption \>5 cigarettes within 3 months before screening.
• History of drug/substance abuse within 6 months before screening, or positive drug abuse screening test.
• Acute illness or concomitant medication occurs from screening to pre-first-dose.

Other illness

• Past history of tuberculosis infection or active tuberculosis at screening.
• Known or suspected history of immunodeficiency, inherited or acquired complement deficiency.
• Positive for HBsAg, anti-HCV, anti-HIV or syphilis-specific antibody at screening.
• Chronic constipation or diarrhea, or other conditions judged by investigator to interfere with fecal sample collection.
• Difficulty swallowing, intolerance to venipuncture, or history of needle-syncope or blood-syncope.

Lab values

• Clinically significant abnormal findings in laboratory tests, physical examination, vital signs, ECG, chest X-ray or abdominal ultrasound at screening.
• QTcF (Fridericia correction) ≥450 ms at screening; or other risk factors for torsades de pointes (TdP), such as heart failure, hypokalemia, hypomagnesemia, family history of long QT syndrome.
• eGFR \<90 mL/min/1.73 m² (calculated by CKD-EPI formula) at screening.

Other

• Required or plan to perform heavy physical labor or strenuous exercise during study participation.
• Pregnant or lactating women, or women of child-bearing potential with positive pregnancy test at screening.
• Cannot tolerate high-fat meal (applies only to subjects in the food-effect sub-study).
• Investigator judges that the subject is unsuitable for this study for any other reason.

• Participants can communicate well with investigators, fully understand the study, volunteer to take part, comply with all study requirements, and sign written informed consent before study procedures.
• Age 18-45 years (inclusive) at informed consent, male or female.
• Weight ≥50.0 kg for males, ≥45.0 kg for females; BMI 19.0-26.0 kg/m² (inclusive).
• Female participants with child-bearing potential, and male participants whose partners have child-bearing potential: no pregnancy, sperm or egg donation from consent to 3 months after last dose, and willing to use study-required contraception.
• For MAD-only participants: receive ACYW135 meningococcal vaccine and pneumococcal vaccine at least 14 days before first dose. No re-vaccination is needed if pneumococcal vaccine was given within 5 years, or ACYW135 meningococcal vaccine within 3 years prior to first dose.