The purpose of this study is to evaluate the safety , tolerability, and pharmacokinetics of ascending single dose Fadanafil （XZP-5849）in Chinese healthy adult male subjects. This is the first XZP-5849 clinical study

XZP-5849 is a selective phosphodiesterase (PDE5) inhibitor. The proposed randomized Phase 1 trial is a double-blind, placebo-controlled, single ascending dose study in approximately 66 Chinese healthy adult male subjects. The study consists of 8 cohorts (1 cohort per dose level). Each subject will participate in only one cohort.

Inclusion Criteria:

• Healthy male subjects 18-45 years old, inclusive.
• Body weight ≥50kg and Body Mass Index: 19.0~25.0 kg/m2, inclusive
• subjects should be willing to take appropriate contraceptive measures during the period of taking the study drug and within 6 months after discontinuation to avoid pregnancy of their partners.

Exclusion Criteria:

• Subjects who have a history of clinical significanct drug allergy (especially those who are known or suspected to have a history of allergy to any PDE-5 inhibitor or its components) or a history of atopic allergic diseases (asthma, urticaria, eczema dermatitis) or severe allergic constitution.
• History of clinically significant ECG abnormality or family history of long QT syndrome (grandparents, parents, brothers and sisters).
• Subjects with serious systemic diseases, such as respiratory, blood, endocrine, cardiovascular and cerebrovascular diseases or mental disorders.
• Subjects who have used over-the-counter drugs, health products, herbal medicine or traditional Chinese medicine within 2 weeks before screening, or are taking foods that affect CYP3A4, such as grapefruit or drinks containing grapefruit (except those who occasionally take paracetamol, but the total maximum dose cannot exceed 1g, and the drug is not allowed to take orally within 48 hours before the first administration).
• Subjects who have used any prescription drugs (especially CYP3A4 inhibitors, nitrates, α receptor blockers, drugs potential to cause QT interval prolongation, etc.) within 4 weeks before screening.