UCB SA shares gained after the Food and Drug Administration approved its psoriasis drug, paving the way for a €4 billion ($4.2 billion) boost to sales.

The Belgian biotech company had faced delays in seeking US clearance for the medicine, which is already approved in other countries including UK, Canada and in Europe under the brand name Bimzelx. UCB will now seek US approval of the treatment for additional applications, according to Emmanuel Caeymaex, executive vice president for immunology solutions and head of US.

UCB shares rose as much as 5.2%, the most since Feb. 2022, to €83.68.

Sales of the drug have rapidly grown since its launch during the pandemic, reaching €52 million in the first half. The company expects global peak sales for Bimzelx at least €4 billion. In a separate statement, UCB said it also got FDA clearance for its Zilbrysq medicine for some patients with generalized myasthenia gravis.

“We see the shares reacting positively to the approvals of Bimzelx and Zilbrysq,” Citigroup analysts including Peter Verdult wrote in a note, maintaining their €84 price target for the stock.

As many as 91% of patients treated with the psoriasis medicine achieved clear or almost clear skin at week 16 in a late-stage trial, the company said in a statement Wednesday, with 59% to 68% getting complete clearance. The disease affects more than 7.5 million adults in the US.

--With assistance from Michael Msika.