ABSTRACT Nearly 1 million percutaneous coronary interventions (PCIs) are performed each year in the US. Approximately 70% of these cases are considered complex and require the treatment of calcified lesions, tortuous vessels, and multi-vessel disease, often with total or sub-totally occluded lesions. Many operators avoid these more complex cases due to the lack of guide catheter support required to effectively deliver coronary stents and other interventional devices. To overcome this limitation, guide extension catheters (GEC) have been developed to help deliver stents in these challenging anatomies. However, GECs are utilized in only 18% of all coronary interventions, mostly as a bailout option, because of their inability to access more distal tortuous lesions in 28% of cases which prevents stent delivery. Blunt ended tubular GECs also have serious safety issues with coronary artery dissection and/or plaque or thrombus embolization. Such limited utilization demonstrates that a significant volume of patients are not treated effectively. Hence, CrossLiner Inc. has developed a novel multi-functional GEC that combines the requirement for deeper catheter intubation with a microcatheter leading tip, and pre- dilatation balloon on the leading element, to allow safe crossing of severe lesions in tortuous coronary vessels, with balloon pre-dilatation, followed by crossing the lesion with the guide extension and then seamless stent delivery. The combination of a GEC with a seamless transition to a microcatheter-balloon provides the capability for easier and safer stent delivery, which can be unsheathed at the lesion as opposed to being delivered from a poorly supported proximal location. This approach enabled by the CrossLiner GEC will substantially improve PCI in patients with complex lesions while reducing risks, procedural duration, radiation/contrast exposure, stent dislodgement, coronary dissection and perforation that occur with current GECs. Data from Phase II bench verification studies demonstrates safety and performance against ISO standards while conforming to design specifications. Formative usability evaluation supports the ease of use and safety, as validated on bench and in vivo which demonstrated a 100% technical success rate, 40% reduction in time to treat, 43% reduction in radiation dose, and 2-3x increase in coronary intubation depth compared to current market leading GECs. These results, value proposition and likely market adoption were corroborated by interviews with 67 interventional cardiologists where over 70% expected improved clinical outcomes and 94% indicated they would use the CrossLiner GEC, rather than a conventional GEC. The company is now ready for final verification and process validation in conjunction with regulatory submission and clearance. Successful execution of these Phase IIB studies will position the CrossLiner GEC system for full commercialization of a highly innovative approach to improve the treatment for compl...