The market is a sea of red on Thursday but that isn't stopping the Mesoblast Ltd (ASX: MSB) share price from rocketing.

In morning trade, the allogeneic cellular medicines developer's shares are up 30% to a 52-week high of $2.57.

Why is the Mesoblast share price shooting higher?

Investors have been hitting the buy button this morning after the company made arguably the most important announcement in its history.

According to the release, the US Food and Drug Administration (FDA) has approved its Ryoncil (remestemcel-L) product as the first mesenchymal stromal cell (MSC) therapy in the United States.

Ryoncil is the only MSC therapy approved in the U.S. for any indication, and the only approved therapy for steroid-refractory acute graft versus host disease (SR-aGvHD) in children 2 months and older, including adolescents and teenagers. It is a life-threatening condition with high mortality rates.

The company highlights that annually in the United States approximately 10,000 patients undergo an allogeneic bone marrow transplant, 1,500 of whom are children.

Approximately 50% develop aGvHD and almost half of those do not respond to steroids, which is the recognised first-line treatment.

There is now hope for people that develop aGvHD. Mesoblast notes that in a single-arm multicenter phase 3 trial of children with SR-aGvHD, 89% of whom had high severity Grade C or Grade D disease, 70% achieved an overall response by day 28 of treatment with Ryoncil. This is a measure that predicts survival in aGVHD.

Ryoncil treatment was not discontinued or interrupted in any patient for any laboratory abnormality, and the full course was completed without interruption in more than 85% of patients.

Management commentary

Commenting on the US FDA's approval of Ryoncil, Mesoblast's chief executive, Dr. Silviu Itescu, said:

We are very pleased that the FDA has granted approval of RYONCIL and are proud of the company's commitment to the GVHD community in bringing this important new treatment to children and families with no other acceptable options.

Dr Itescu appears optimistic that this could be the first of further approvals of products in its portfolio. He adds:

With RYONCIL approval by FDA, Mesoblast has demonstrated the ability to bring the first MSC product to market. We will continue to work closely with FDA to obtain approval of our other late-stage products, including REVASCOR for cardiovascular diseases and rexlemestrocel-L for inflammatory pain indications, as well as expanding the indications for RYONCIL in both children and adults with inflammatory conditions.

The Mesoblast share price is now up approximately 750% since this time last year.