This Phase I study is a randomized, double-blind, placebo-controlled, dose-escalation trial conducted at a single center. It consists of two parts:

Part 1 (SAD): Evaluates the safety, tolerability, and pharmacokinetics (PK) of single ascending intravenous doses of JKN2501 in healthy adults. Biological samples (blood, urine, feces) will be collected for PK analysis.

Part 2 (MAD): Evaluates the safety, tolerability, and PK of multiple ascending intravenous doses of JKN2501 in healthy adults.

Dose levels may be adjusted based on emerging safety, tolerability, and PK data from preceding cohorts.

Inclusion Criteria:

• Voluntary informed consent; able to comply with study requirements and communicate effectively.
• Healthy subjects aged 18-45 years (inclusive) at screening.
• BMI 19.0-26.0 kg/m² (inclusive); weight ≥50 kg (male) or ≥45 kg (female).
• Vital signs, physical examination, ECG, laboratory tests, chest X-ray, and abdominal ultrasound results judged as normal or clinically insignificant by the investigator.
• Agreement to use effective non-pharmaceutical contraception from signing ICF until 90 days after last dose; no sperm/egg donation plans during this period.

Exclusion Criteria:

• Pregnant/lactating women; positive pregnancy test; unprotected sex within 2 weeks prior to dosing.
• Investigator-determined history or presence of clinically significant disorder that may affect safety or trial participation.
• Use of drugs known to inhibit/induce hepatic metabolism within 4 weeks, or any medication (prescription, OTC, herbal, vitamins) within 2 weeks prior to dosing; planned use during the trial.
• Major surgery within 3 months prior to screening or planned during trial; history of surgery potentially affecting results.
• History of febrile illness or active infection within 2 weeks prior to screening.
• Blood loss/donation >400 mL within 3 months prior to screening, or received blood products; plans to donate blood during trial or within 30 days after last dose.
• History of significant food/drug allergy, or allergy to JKN2501/excipients.
• Excessive alcohol consumption; inability to abstain from alcohol from 48h pre-dose until end of study.
• Smoking ≥5 cigarettes/day within 3 months prior to screening; inability to abstain from smoking from 48h pre-dose until end of study.
• History of drug abuse; positive urine drug screen at baseline (Day -1).
• Positive alcohol breath test at baseline (Day -1).
• Participation in another interventional clinical trial within 3 months prior to screening or planned during this trial.
• Estimated glomerular filtration rate (eGFR) <90 mL/min.
• Serum total calcium below lower limit of normal at screening.
• Investigator-determined unsuitable venous access for PK sampling/infusion, or history of adverse symptoms/phobias related to infusion/phlebotomy.
• Excessive daily intake of tea, coffee, or caffeinated beverages within 3 months prior to screening.
• Consumption of grapefruit, Seville oranges, caffeine, or xanthine-rich foods/beverages within 48h prior to first dose; inability to abstain during the trial.
• History of QTc prolongation; or investigator-determined clinically significant ECG abnormalities at screening/baseline.
• Any other condition deemed by the investigator to make the subject unsuitable for participation.