Mesoblast (ASX:MSB) has released more data from its halted COVID-19 trial, saying its stem cell treatment apparently significantly reduced mortality in severely ill younger patients – but the controversial biotech isn’t sure it will seek an emergency use authorisation for it.

Mesoblast’s remestemcel-L infusion reduced death by 46 per cent in ventilator-dependent patients under age 65, but not in patients 65 and older, the study indicated. When remestemcel-L was combined with the anti-inflammatory medication dexamethasone, it appeared to cut mortality by 75 per cent, compared to when dexamethasone was used alone.

An independent committee stopped the US trial in December after 222 patients had been enrolled, rather than the 300 planned, because the data monitoring board judged the study was unlikely to meet its primary endpoint of a 43 per cent reduction in death at 30 days.

Mesoblast shares plunged by more than a third on the news, and have declined further in the past few months, yesterday closing at a one-year low of $1.83.

At 10.18am this morning, Mesoblast shares were up 10.9 per cent to $2.03, still down significantly from over $5 in September.


Results ‘exciting’, ‘important’

On a conference call with analysts this morning, Mesoblast chief executive Dr Silviu Itescu called reduction in mortality “exciting” and “very important” and said that perhaps a different dosing regimen might be more effective in older patients, whom he noted have more comorbidities (health problems).

Itescu and chief medical officer Dr Fred Grossman said the company was still in discussions with the FDA about using remestemcel-L to treat graft-versus-host disease in children, a complication of bone marrow transplants.

But Itescu said it was too early to say whether Mesoblast would seek an emergency use authorisation with the FDA for using remestemcel-L as a COVID-19 treatment.

“As noted, this study was stopped before its completion, and the signal detection work that we’ve done has been something that’s very very important, and significant enough to warrant these discussions with the FDA for suitable paths forward,” Dr Grossman said.

There’s no COVID-19 treatment that substantially reduces mortality, he said.