BASEL, Switzerland — AveXis Inc.’s parent company said sales of its flagship gene therapy increased by $26 million over the last quarter, signalling strong demand for the drug due to start production in its Longmont plant this year.

Novartis AG (NYSE: NVS) said it sold $186 million worth of doses of Zolgensma, a one-time therapy for young children with spinal muscular atrophy, for the period. It sold $160 million in the quarter before in its first full quarter on the market, far outpacing analyst expectations at that point.

The drug is the world’s most expensive at $2.1 million per dose, meaning Novartis sold an additional 12 doses on top of its previous sales in Q3 2019.

AveXis is based in the Chicagoland area but recently began the process of getting federal approval to make Zolgensma at the 692,000-square-foot plant in Longmont formerly owned by AstraZeneca PLC (NYSE: AZN). At full capacity, the plant could produce between 800 to 1,200 doses to treat SMA, which treats a genetic disorder that prevents newborns from developing the strength needed to move body parts unassisted. Most patients die before they reach the age of 2.

The company also said newborn screening for SMA in the U.S. rose from 30 percent to nearly 50 percent between Q3 and the end of 2019, and it expects as much as 70 percent of newborns to be screened for the disease by the end of 2020.

In response to criticism over pricing, Novartis announced last month it would give away 100 doses of the drug outside of the U.S. in 2019 and 2020 in a lottery-like giveaway.