CellProthera has published peer-reviewed results from its phase 1/2b Excellent trial in JACC: Heart Failure, evaluating the safety and feasibility of ProtheraCytes in patients with heart failure after a severe myocardial infarction (MI).

The open-label, randomised controlled study enrolled patients about one week after a large heart attack, with an average left ventricular ejection fraction of 35%. The company said the data support further development of expanded CD34+ stem cells delivered by transendocardial injection.

The trial was not designed to demonstrate efficacy but showed encouraging trends. Patients treated with ProtheraCytes recorded a 9% average reduction in left ventricular end-systolic volume index, a 50% reduction in severely damaged heart tissue at six months, and a 70% drop in NT-proBNP levels at three months.

ProtheraCytes were well tolerated. No adverse drug reactions or deaths were reported. One of 33 treated patients (3%) required hospitalisation for heart failure within six months, compared with three of 16 patients (19%) in the standard-care group, one of whom later received a heart transplant.

There were nine procedure-related complications in the treatment group, all of which resolved. The company said future procedures will use improved imaging, planning and training to further reduce risk.

“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,” said Prof Jérôme Roncalli.

CellProthera’s automated expansion platform produced each patient’s own CD34+ stem cells with more than 90% purity and almost 98% viability. The fresh cells were delivered to catheter laboratories in France and the UK within hours for administration.

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

The Excellent trial analysed 49 patients: 33 received ProtheraCytes plus standard care, and 16 received standard care alone. Building on these findings, CellProthera is preparing larger trials to confirm longer-term outcomes and further evaluate safety in high-risk populations.