A Safety/Efficacy Study of Alprostadil Liposomes for Injection to Treat Lower Extremity Arteriosclerosis Obliterans

Inclusion Criteria: * An established clinical history of Atherosclerotic Occlusive Disease of the Lower Extremities in accordance with the definition by Chinese Medical Association(2015). * Age\>40 * Atherosclerotic Occlusive Disease of the Lower Extremities diagnosis * Arterial ischemia of the lower extremities pulsation has been weakened or disappeared. * Ankle brachial index(ABI) less than or equal to 0.9 * Diagnosis of artery stenosis or occlusion with imaging tests,including Doppler ultrasonography,CT angiogram(CTA),magnetic resonance angiography (MRA) or digital subtraction angiography(DSA) within 1 month prior to Screening. * Fontaine stage classification:Stage II * Distance of asymptomatic disease and claudication between 50m to 800m(The treadmill setting:pace at 3 km/h,incline at 12%).Subjects have intermittent claudication twice within 1 week prior to enrollment visit(Baseline is defined as the first measurement.Change from baseline in P-values less than or equal to 25%). * Age:80 years old or younger. * Intermittent claudication has been in stable condition in the last 6 months.And there was no history of exacerbations within 3 months prior to enrollment visit. * Informed Consent:A signed and dated written informed consent prior to study participation. Exclusion Criteria: * Subjects who have cardiac disease including caradiac failure,arrhythmias,coronary disease,mitral or aortic stenosis.Subjects with a recent history of myocardial infarction within the past 6 months are to be excluded. * Subjects who have pneumonedema,pulmonary infiltrates,interstitial pneumonia,severe chronic obstructive airway disorders or respiratory insufficiency confirmed by clinical examination. * Liver:Subjects with abnormal liver function tests defined as aspartate aminotransferase(AST) or alanine aminotransferase(ALT) greater than equal to 1.5 times upper limit of normal,as well as a diagnosis of primary liver disease will be excluded. * Renal:Subjects with abnormal kidney function tests defined as Creatinine clearance rate(SCr) greater than or equal to upper limit of normal. * Clinically Uncontrolled Hypertension:Subjects who have clinically significant uncontrolled hypertension(Systolic blood pressure:greater than or equal to 180mmHg;Or diastolic blood pressure:greater than or equal to 110mmHg). * Ankle systolic pressure is less than or equal to 50mmHg. * Subjects with affected limbs surgery or endovascular treatment within 3 months prior to Screening.Subjects who received Prostanoids within the past 1 week are to be excluded. * Subjects who received walking rehabilitation training successfully within the past 6 months. * Subjects with a diagnosis of other diseases such as lower limb joint disorder,spinal lesions,neuropathy,serious lung and heart conditions which may impact intermittent claudication will be excluded. * Subjects who have inflammation of the vascular disease including Takayasu's arteritis,edema perivascular. * Subjects with active peptic ulcerease or bleeding tendency will be excluded. * Glaucoma:Subjects with a diagnosis of glaucoma or high intraocular pressure will be excluded. * Subjects who are medically unable to withhold their vasodilator including naftidrofuryl,pentoxy,buflomedil or cilostazol will be excluded. * Subjects who received any powerful analgesic within 1 month perior to Screening. * Subjects with a history of psychiatric disease or Alzheimer's Disease. * Cancer:Subjects with a diagnosis of cancer will be excluded. * Drug Allergy:Subjects who have a history of any componet of Alprostadil Injection. * Previous Participation:Subjects who were previously enrolled in any clinical trial within 1 month period to Screening. * Pregnancy:Women who are pregnant or lactating or women of childbearing potential who are not using an acceptable method of contraception. * Subjects,who in the opinion of the Investigator,will not be fit for this study.