This is a multicenter, open study to evaluate the long-term safety and efficacy of TPN171H in men with erectile dysfunction.

Inclusion Criteria:

• 18 years to 75 years (inclusive);
• Males with ED at least 3 months;
• IIEF-5 ≤ 21 at visit 1;
• Patients in a stable, heterosexual relationship during the study;
• At the end of the untreated baseline period, the following conditions are met：（1）The subject must make at least four attempts at sexual intercourse during the untreated baseline period. （2）At least 50% of attempts during this period must be unsuccessful,（unsuccess means at least one of the first three questions should be answered "No" in SEP）.（3）5≤IIEF-EF≤25.
• Patients who are willing to have 4 or more attempts of sexual intercourse per month, demonstrated compliance with the study protocol, including drug administration, diary completion, and scheduled study visits, during the qualifying trial;
• Patients who are willing to take proper contraceptive during the study and within 3 months after the last dose;
• Patients who have voluntarily decided to participate in this study, and signed the informed consent form.

Exclusion Criteria:

• Patients who have a history of hypersensitivity to other PDE5 inhibitors or TPN171H;
• Patients with anatomical malformations of the penis;
• Patients with primary hypoactive sexual desire;
• Patients with ED, which is caused by any other primary sexual disorder;
• Patients with ED, which is caused by spinal injury or have had a radical prostatectomy or other surgery;
• Patients who have a penile implant;
• Patients who do not respond to marketed PDE5 inhibitors or have adverse reactions that lead to drug discontinuation;
• CYP3A4 potent inhibitors, moderate inhibitors, and potent inducers need to be used during the trial or discontinued for less than 31 days before enrollment;
• Subjects who are taking nitrate or NO donor drugs, guanylate cyclase agonists and cannot be discontinued during the trial;
• Patients with the following cardiovascular disease: Myocardial infarction or stroke within the last 6 months; Unstable angina or angina occurring during sexual intercourse; New York Heart Association Class 2 or greater heart failure in the last 6 months;
• Uncontrolled hypotension (<90/60mmHg) or uncontrolled hypertension (≥180/110mmHg);
• Patients with diabetic complications (diabetic nephropathy, peripheral neuropathy);
• Patients with hepatic or renal dysfunction as per the following: AST, ALT>3*ULN, serum creatinine exceeds 50% of the upper limit of normal value;
• Patients with active gastrointestinal ulcers and bleeding disorders;
• Patients who have a history of NAION, or with a known genetically degenerative retinopathy, including retinitis pigmentosa;
• Patients who have a history of sudden decrease or loss of hearing;
• Patients with a history of severe central nervous system injury or peripheral muscular neurological disease in the past 6 months;
• Patient with a history of malignancy;
• Patients with significant neurological abnormalities who are unable or unwilling to cooperate;
• Patients whose partner is breastfeeding/pregnant/trying to become pregnant, has a gynecological disease or is restricted in their activities during treatment;
• Patients who have used other drugs in clinical trials within the last 1 month;
• For other reasons besides the aforementioned cases, patient whose participation is deemed inappropriate.