Stem cell product company Mesoblast has raised $US90 million ($138 million) of fresh funds as it makes a major push with trials and a scale-up in manufacturing of its key drug candidate to treat seriously ill COVID-19 patients.

Investors bought in at $3.20 per share price, a 7 per cent discount the close of trading on May 8. The fresh fund raising effort comes on the back of $75 million placement to build product inventory and a targeted American sales force in October.