Mesoblast defends stem cell therapy for heart failure after trial miss

Mesoblast’s stem cell-based therapy was unable to reduce heart failure (HF) patients’ reliance on a left ventricular assist device (LVAD) in a phase 2 trial, sparking a steep slide in its shares.

The Australian biotech said the trial showed that injections of MPC-150-IM (mesenchymal precursor cells) into the myocardium when the LVAD was implanted were not able to wean patients off the devices entirely, which it put down to blood clots in the devices that reduced the number of attempts.

The therapy did however allow a subgroup of patients with ischemic HF to be weaned off the LVADs temporarily, and there was a significant 76% reduction in major gastrointestinal bleeds plus a 65% drop in bleed-related hospitalizations in patients treated with the therapy. Mesoblast says GI bleeds are “a major cause of morbidity and increased cost” with LVAD implants and affect up to 40% of recipients.

CEO Silviu Itescu, who told Australia’s Stockhead news service that share price crashed on the announcement—which carved almost a third off the value of the ASX-listed stock—had been “misunderstood by the market.”

He insisted that the study has set up a “pathway for potential regulatory approval” in end-stage HF patients in the prevention of GI bleeds, although he added that the FDA has confirmed that temporary weaning off LVAD wouldn’t be considered “clinically meaningful in and of itself.”

Last year, a few months after Teva decided it no longer wanted to partner on the therapy, Mesoblast opted to continue a phase 3 trial of MPC-150-M after an interim look at the blinded data suggested there was no safety issue.

That 600-patient study—which is well on the way to being fully enrolled—is designed to see if the therapy can reduce nonfatal heart failure-related major adverse cardiac events such as death, needing a pacemaker implanted or undergoing a heart transplant. A lot is now riding on the outcome of that trial as Mesoblast tries to keep up with its main rivals in the category.

One of those is California biotech BioCardia, which earlier this year presented data on the first 10 patients in its phase 3 CardiAMP-HF trial of stem cells harvested from HF patients. That showed improvements in six-minute walk tests as well as New York Heart Association class, backing up earlier positive data in phase 2. The biotech is also testing this approach in patients with chronic myocardial ischemia.

Among other players, CardioCell presented mixed results on its candidate in 2016 but has pressed ahead with development and is planning a phase 2a study in LVAD patients, while Celyad's C-Cure product failed to meet its objectives in its phase 3 CHART trial.

Meanwhile, away from the cardiovascular arena, Mesoblast is also developing a mesenchymal precursor cell-based therapy for diabetes, called rexlemestrocel-L (MPC-300-IV), that EvaluatePharma has suggested could become a $227 million product by 2024. That program is in midstage trials.

Its lead candidates are remestemcel-L for graft-versus-host disease, which is approved and sold in Japan by licensee JCR Pharmaceuticals as Temcell and is in phase 3 elsewhere, and MPC-06-ID for chronic lower back pain.