The S&P/ASX 200 Index (ASX: XJO) is having a volatile session but is currently on course to record a small gain. In early afternoon trade, the benchmark index is up slightly to 8,208.5 points.

Four ASX shares that are rising more than most today are listed below. Here's why they are climbing:

AVITA Medical Inc (ASX: AVH)

The AVITA Medical share price is up 5% to $4.00. Investors have been buying this regenerative medicine company's shares after the United States Food and Drug Administration (FDA) approved its premarket approval (PMA) supplement for RECELL GO mini. AVITA CEO, Jim Corbett, said: "The FDA approval of RECELL GO mini strengthens our ability to provide clinicians with fit-for-purpose solutions that meet the diverse needs of patients with full-thickness wounds. By introducing a treatment option specifically for smaller wounds, we are expanding the accessibility of RECELL to a wider range of patients."

GenusPlus Group Ltd (ASX: GNP)

The GenusPlus Group share price is up 4% to $2.55. This follows news that the essential services provider has won another big contract. According to the release, GenusPlus has been awarded a contract for Stage 1 of TasNetworks' North West Transmission Developments (NWTD) project. The company notes that the staged contract commences with the award of the early contractor involvement phase of NWTD Stage 1 which is worth approximately $42 million to GenusPlus.

Mesoblast Ltd (ASX: MSB)

The Mesoblast share price is up 1.5% to $2.57. This biotechnology company's shares have been on fire this week after announcing some big news. Mesoblast revealed that the US FDA has approved its Ryoncil (remestemcel-L) product as the first mesenchymal stromal cell (MSC) therapy in the United States. It notes that Ryoncil is the only MSC therapy approved in the U.S. for any indication. It is also the only approved therapy for steroid-refractory acute graft versus host disease (SR-aGvHD) in children 2 months and older, including adolescents and teenagers.

Polynovo Ltd (ASX: PNV)

The Polynovo share price is up a further 1.5% to $2.09. This medical device company's shares have been pushing higher this week after it released a trading update. That trading update revealed that the company achieved its first $10 million sales month in November. This means that year to date, Polynovo's revenue is now $49.6 million. This is an increase of $10.1 million or 25.4% on the prior corresponding period.