Abstract Background Chronic ischaemic heart failure (CIHF) remains an important health problem on the patient/family- and society level. In animal models, Wharton's jelly (umbilical cord matrix) multipotent stem cells (WJMSCs) effectively promote angiogenesis, can differentiate to cardiomyocytes, and drive functional myocardial regeneration. Effective uptake of regenerative cells in ischaemic-impaired tissue is fundamental for any therapeutic effect. Purpose To evaluate safety and myocardial uptake of WJMSCs transcoronary transfer in CIHF applied as a novel myocardial regeneration strategy employing allogenic yet hypo-immunogenic, off-the-shelf “unlimited” source of therapeutic cells (NCT03418233 pilot cohort). Material and methods In ten consecutive patients (age 62.6±2.5), with stable CIHF and no current need for revascularization (LVEF 29.3±3% by echo and 26.3±6% by SPECT; NT-proBNP 1746±329pg/mL; myocardial scar tissue 39.9±3.9% by SPECT) and patency of at least two major native coronary arteries or by-pass graft(s), the CardioCell Investigational Medical Product, based on 30x106 WJMSCs, was administered to viable yet hypokinetic segments using a novel algorithm including a dedicated catheter for transcoronary delivery of cellular therapies. The cells were labeled with 99mTc-extametazime to routinely evaluate their myocardial uptake magnitude. Results No symptoms or signs of novel myocardial ischaemia occurred with cell delivery and no patient showed any adverse periprocedural events. One hour after administration, myocardial WJMSCs uptake (SPECT) was 40.3±6%; see Fig for a typical raw data image. By 6 months there were no adverse events in the study cohort. Figure 1 Conclusions This work indicates safety and unprecedented high-grade myocardial uptake of WJMSCs in CIHF patients. Together with animal data, this provides basis for continued assessment of this strategy in an endpoint-powered randomized controlled clinical trial employing CardioCell as an “unlimited” off-the-shelf cellular therapy strategy. Acknowledgement/Funding K/ZDS/005644 and 265761 (National Centre for Research and Development STRATEGMED)