• Mesoblast’s six-year study into using a cell stem injection to prevent heart failure failed to meet clinical endpoints
  • Rexlemestrocel-L appeared to reduce deaths in patients with mild heart failure but not hospitalisations
  • But Mesoblast says the findings are dramatic and it will ask the FDA to approve the treatment

Mesoblast (ASX:MSB) shares have dropped more than 12 per cent to a nearly one-month low after a six-year trial investigating using its stem cell treatment to treat advanced chronic heart failure delivered confusing results.

The injection of stem cells into the heart appeared to prevent deaths in patients with mild symptoms but not hospitalisations. That was the primary goal of the study, which Mesoblast says is the largest and most rigorous cell therapy trial ever performed.

In the Phase III trial involving 537 patients with advanced chronic heart failure, the group treated with an injection of rexlemestrocel-L had 60 per cent fewer heart attacks and strokes than those treated with a sham treatment.

Also, in the 206 patients with mild heart failure symptoms, those who received rexlemestrocel-L suffered 60 per cent fewer deaths than those in the placebo group.

But the trial failed to meet its predefined primary endpoint in that the treatment failed to reduce hospitalisations during the follow-up period, which lasted an average of 30 months.

At 11.36am, MSB shares were down 12.3 per cent to $3.98, their lowest level since mid-November.


‘A quite dramatic finding’

But Mesoblast said that overall the study was incredibly positive and that it would seek regulatory approval in the United States as well as a large commercial partner to meet what it sees as a huge market opportunity.

On a conference call with analysts this morning, Mesoblast chief executive Dr Silviu Itescu said that rexlemestrocel-L had delivered a “dramatic reduction in mortality” that may “change the paradigm of how patients with advanced cancer may be treated.”

He said Mesoblast planned to meet again shortly with the US Food and Drug Administration and ask for drug approval of rexlemestrocel-L, (REVASCOR®), which consists of an injection of 150 million mesenchymal precursor cells directly into the heart.

“This is a very surprising finding and quite dramatic,” he said. “And I think that any therapy that has this degree of reduction in mortality in a well-conducted randomized placebo-controlled study of this size has to be taken seriously in terms of its ability to completely change the natural course of the disease.

“So, we will be having those discussions. I think there are clear pathways towards accelerated approval.”

Dr Itescu said that the rexlemestrocel-L injection may not have reduced recurrent hospitalisations because advanced heart failure patients are “brittle” and may need hospital treatment to be stabilised.

“It appears our therapy does not have an impact on those types of outcomes,” he said.

Mesoblast believes that the stem cell injection works to reduce severe inflammation in the heart muscle.

Other drugs in this patient population have reduced mortality by less than 20 per cent, Dr Itescu said.

‘A very large market opportunity’

The drug would be aimed at patients with class 2 heart disease – mild symptoms such as shortness of breath or angina, but who did not yet have problems walking short distances.

“That would be our target market in the patient journey, in terms of that being a very large market opportunity,” Dr Itescu said.

“Clearly, we will be looking for a strategic commercial partner that has strength and commitment in the commercial channels that will be required to make this product available to these large numbers of patients. We have ongoing discussions with a number of large pharmaceutical companies in this space.”

Dr Itescu said that a rexlemestrocel-L injection would not displace other therapies, but would be a “single delivery of a therapeutic that gives three o=o four years at least, of mortality benefit and reduction in major vascular events like heart attacks and stroke.”