The S&P/ASX 200 Index (ASX: XJO) is on form again after returning from the Christmas break. At the time of writing, the benchmark index is up 0.4% to 8,255.7 points.

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

Bowen Coking Coal Ltd (ASX: BCB)

The Bowen Coking Coal share price is up almost 17% to 7 cents. This morning, this coal miner released a trading update which revealed that it has recorded 544Kt of coal sales for the quarter to date. Management notes that this represents a new quarterly sales record for the company and a 31% improvement from the September quarter. CEO Daryl Edwards said: "The Burton Mine Complex continues at steady-state and we are proud to report another record being achieved, this time a quarterly coal sales record."

DroneShield Ltd (ASX: DRO)

The DroneShield share price is up 13% to 72.5 cents. This is despite there being no news out of the counter drone technology company. However, with its shares falling heavily in recent months, investors may believe that a buying opportunity has opened up. Despite today's gain, the DroneShield share price remains down 56% over the past six months.

Mesoblast Ltd (ASX: MSB)

The Mesoblast share price is up a further 8% to $2.76. This biotechnology company's shares have been racing higher this week thanks to the release of a big announcement. That announcement revealed that the US 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. 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. This could be a positive sign for its other stem cell therapies that are seeking approval.

St Barbara Ltd (ASX: SBM)

The St Barbara share price is up 8.5% to 21.7 cents. This appears to have been driven by bargain hunters swooping in after the gold miner's shares were sold off earlier this week. Investors rushed to the exits after the company revealed that the Papua New Guinea Internal Revenue Commission (IRC) has delivered correspondence to Simberi Gold's tax agent. That correspondence contains details of tax assessments with additional taxes, inclusive of a 200% penalty imposition, that amount to PGK 523 million. This is the equivalent to approximately A$210 million.