Program discontinued to persue alternate indications.

The purpose of this study is to evaluate the safety and efficacy of MST-188 in subjects receiving catheter-directed rt-PA for acute lower limb ischemia and to evaluate whether treatment with MST-188 results in more rapid thrombolysis of the occlusion and more rapid tissue perfusion in the effected blood vessel.

Inclusion Criteria:

• Age ≥30 to <80
• Symptoms consistent with ALI in target lower limb classified as Rutherford Category IIa or IIb
• Subject is hospitalized or in the process of hospitalization for the treatment of ALI
• Angiographic confirmation of thrombotic lower limb arterial occlusion

Exclusion Criteria:

• Prosthetic bypass graft occlusion within 1 month of implantation or autogenous graft occlusion within 6 months of placement
• Treatment with a thrombolytic agent within the last 48 hours
• Subject's laboratory results indicate inadequate organ function
• NYHA Class IV congestive heart failure
• Prior major amputation of the target limb
• Other complications or contraindications for receiving rt-PA, anticoagulants, or contrast media