CellProthera has published the first peer-reviewed results from its Excellent Phase 1/2b trial in JACC: Heart Failure, reporting safety and feasibility findings for its autologous stem cell therapy ProtheraCytes in patients with severe heart failure following a myocardial infarction.

The trial enrolled patients one week after a major heart attack with significant myocardial damage and an average left ventricular ejection fraction of 35%. While not designed to prove efficacy, the study reported early signs of functional benefit alongside a manageable procedural risk.

Patients treated with ProtheraCytes showed an average 9% reduction in left ventricular end-systolic volume index, a 50% reduction in severely damaged heart tissue at six months and a 70% average drop in NT-proBNP levels at three months.

No adverse drug reactions were reported and there were no deaths. Over six months, one of 33 treated patients required hospitalisation for heart failure, compared with three of 16 in the standard care group, one of whom went on to receive a transplant. There were nine procedure-related complications in the active group, but all patients recovered. CellProthera said future procedures will be refined with improved imaging, planning and operator training.

Prof Jérôme Roncalli said: “The fact that several cardiac markers improved in the first six months in this population with severe MI encourages us to further investigate it in a larger study with longer follow-up and all the necessary safeguards in place to reduce the risk of procedural complications.”

The company also highlighted the robustness of its automated expansion platform, which consistently produced patients’ own CD34+ stem cells at clinical scale. Average purity was over 90% and viability nearly 98%, with fresh cells delivered to catheter labs in France and the UK within hours of preparation.

“These results demonstrate that ProtheraCytes can be manufactured and delivered to some of the most fragile post-MI patients while maintaining exceptional quality,” said Matthieu de Kalbermatten, CEO of CellProthera.

The Excellent trial was a prospective, multicentre, open-label, randomised controlled study in France and the UK. Of 49 patients analysed, 33 received ProtheraCytes by transendocardial injection on top of standard care, and 16 received standard care alone. CellProthera is now preparing larger studies to confirm long-term benefits and further evaluate safety in this high-risk population.