A prospective, multi-center, double blind, 2 stage, placebo-controlled, phase II study, evaluating acute intra-coronary injected collagenase prior to routine standard-of-care percutaneous revascularization procedures in subjects with chronic total coronary artery occlusions (CTOs).

Inclusion Criteria:

• Male or females patients > 18 years of age who has a clinically driven, planned PCI of the target CTO, in a major epicardial coronary artery, without planned revascularization of other coronary stenosis/stenoses in major epicardial segments.
• Target CTO must be greater than or equal to 3 calendar months prior to Screening
• Target CTO must meet protocol defined criteria for entry
• Patient is receiving a course of optimal anti-ischemic medical therapy (at least 2 anti-anginal agents or the maximum tolerated anti-anginal therapy)

Exclusion Criteria:

• Documented chest radiation exposure > 4.0 Gray within 8 weeks of Day 0
• Target vessel is not an occluded stent, saphenous vein graft
• Patient had ACS < 4 weeks from Screening, attributable to any coronary vessel
• Patient has non-healed dissection plane extending to a point adjacent to the coronary lumen distal to the target CTO
• Patient has a known or suspected target vessel perforation within 30 days of Day 0
• Angiographic exclusion criteria as defined in the protocol