Males and females 40 to 80 years of age, inclusive.

Clinical diagnosis of PAD, secondary to atherosclerosis, in both lower limbs, confirmed by objective evidence:

Symptoms of severe intermittent claudication (IC) in at least 1 lower limb persisting for ≥ 6 months

Patients with a peak walking time (PWT) of 1 to 10 minutes (inclusive) using the standardized exercise treadmill test at each of the 2 consecutive treadmill tests performed at least a week apart during the Screening period. The mean PWT from the 2 consecutive visits must also be 1 to 10 minutes (inclusive).

During Screening, patients must demonstrate consistency of PWTs between 2 standardized exercise treadmill tests (Walk 1 and Walk 2) performed at least 1 week apart.

Consistency of the PWT between the 2 visits is achieved if the difference between PWT at Walk 1 and Walk 2 is ≤ 25% of the higher of the 2 PWTs ([higher PWT - lower PWT]/higher PWT).

If the difference between PWT at Walk 1 and Walk 2 is > 25% of the higher of the 2 PWTs, a third treadmill test (Walk 3) may be performed at the discretion of the Principal Investigator between 7 and 14 days following Walk 2. The variability in PWT warranting the performance of Walk 3 must be secondary to circumstances that may contribute to the observed variation (e.g., prior exertion, inconsistent timing, ingestion of a meal within 4 hours, etc). To qualify for the study, the difference between PWT at Walk 2 and Walk 3 must be ≤ 25% of the higher of the 2 PWTs ([higher PWT - lower PWT]/higher PWT).

An acceptable mean PWT must be achieved within 4 weeks of treatment administration.

Patients have been considered for other potential treatment options including exercise rehabilitation, smoking cessation, and pharmacological therapy prior to enrollment.

Claudication severity, concomitant medications for the treatment of CAD, PAD, and IC, smoking status and exercise habits should be clinically stable for 3 months prior to Screening.

Patients who are committed to following the protocol requirements as evidenced by written informed consent.

Patients with Critical Limb Ischemia (CLI). (NOTE: Rutherford Category 4: ischemic rest pain, Rutherford Category 5: non-healing ischemic ulcers and minor tissue loss, Rutherford Category 6: non-healing ischemic ulcers and major tissue loss)

Patients in whom arterial insufficiency in the lower extremity is the result of acute limb ischemia or an immunological or inflammatory non-atherosclerotic disorder (eg, thromboangiitis obliterans [Buerger’s Disease]) and systemic sclerosis [both limited and diffuse forms]).

A PAD-specific surgical revascularization procedure within 6 months of enrollment or a percutaneous procedure within the previous 3 months, or patients likely to require a revascularization procedure within 6 months after enrollment.

Patients with aortoiliac disease that limits inflow in either leg:

Patients with concomitant aortoiliac disease (i.e., patients with a significant component of inflow disease in the distal aorta, common or external iliac, or proximal common femoral artery) as assessed by an imaging modality (e.g., segmental limb pressures and waveform analysis, duplex ultrasound scanning, magnetic resonance angiography, or radio-contrast arteriogram) performed within 1 year prior to Screening. If subject has had a bypass after the imaging study, then documentation of graft patency is required within 6 months prior to randomization.

If it is suspected at Screening that a patient has aortoiliac disease based on vascular examination, an imaging modality (e.g., segmental limb pressures and waveform analysis, duplex ultrasound scanning, magnetic resonance angiography, or radio-contrast arteriogram) must be performed to rule it out if there is not one available within the times specified above.

Patients in whom walking impairment due to pain in the index leg is the result of these nonatherosclerotic comorbid conditions: venous claudication, chronic compartment syndrome, peripheral nerve pain (e.g., severe peripheral neuropathy), pseudoclaudication caused by spinal cord compression, or acute limb ischemia which, in the Principal Investigator’s judgment are severe enough to confound the assessment of the patient’s IC.

Conditions other than IC of significant severity that could confound PWT on the standardized exercise treadmill test causing premature or inconsistent termination of exercise (e.g., angina pectoris, heart failure [New York Heart Association {NYHA} Classes III and IV], respiratory disease [e.g., chronic obstructive pulmonary disease], orthopedic disease, neurological disorders, rheumatologic disorders [e.g., severe degenerative joint diseases], dyspnea, fatigue, prior lower limb amputation, including amputations proximal to the metatarsal or phalangeal joints).

Presence or history of cancer within 5 years or not current with recommended screening guidelines for colorectal, lung, prostate, breast, cervical, and uterine cancers, with the exception of low grade and fully resolved non-melanoma skin malignancy.

Patients with a well-defined clinical or genetic disorder predisposing to malignancy should be excluded (e.g., von Hippel Lindau, familial polyposis coli, BRCA1, BRCA2, etc).

Patients with baseline funduscopic evidence of active proliferative diabetic retinopathy, preproliferative diabetic retinopathy, or wet AMD AND/OR Patients with a history of treatment for active proliferative diabetic retinopathy or wet AMD within 5 years of study participation.

Diabetes type 1 (juvenile onset)

Poorly controlled type 2 diabetes (ie, HbA1C >10%) at Screening

Active hepatitis defined as clinically significant increase in liver enzymes (ie, 3 times the ULN) or other current infectious disease

Patients with symptoms of respiratory infection at time of Screening and/or randomization period and/or patients who have been on systemic or oral antibiotics for active infection within 2 weeks of study drug administration.

Patients with clinically significant abnormal hematology (eg, hematocrit < 30%, white blood cell count > 10,000), blood chemistry, renal, hepatic, or other laboratory parameters that could be the result of an underlying 2.5 mg/dL), as judged≥malignancy or systemic infection (e.g., serum creatinine by the investigator.

Patients with the following comorbidities who may not be healthy enough to successfully complete all protocol requirements or in whom results may be particularly difficult to assess:

Patients with a known allergy to the vehicle, placebo control, or any other medications or imaging agents required for participation in this study.

Fertile women who are pregnant, nursing, or using either no or an inadequate form of contraception.

Fertile men who are not willing to use barrier-type contraception.

Patients with a recent history of alcoholism or drug abuse, or severe emotional, behavioral or psychiatric problems, who may not be able to adequately comply with the requirements of the study.

Patients receiving experimental medications or participating in another study using an experimental drug or experimental procedure within 30 days of screening into this study.

Patients previously enrolled in a prior angiogenic gene therapy clinical study, unless patient was a known placebo patient.