(Bloomberg) -- Bluebird Bio Inc.’s first gene therapy, a treatment for an inherited blood disorder, was cleared by European Union regulators, another milestone for the field following approval of Novartis AG’s $2.1 million treatment for a lethal childhood disease.

Bluebird’s Zynteglo was authorized in Europe for patients 12 years and older afflicted with a beta thalassemia, the Cambridge, Massachusetts-based company said in a statement Monday. While the company didn’t specify a price, it has said that costs for the one-time therapy will be capped at $2.1 million.

Drug companies including Bluebird and Novartis are seeking to overcome a slow financial start for gene therapies. Only a handful of patients received Strimvelis, a $665,000 treatment for a rare immune disorder, before GlaxoSmithKline Plc offloaded it to Orchard Therapeutics Plc, and UniQure NV in 2017 withdrew its $1 million gene therapy for another rare condition because of extremely limited use.

Gene therapies offer potential cures for a range of devastating diseases, aiming to fix their root cause with a single dose. While prices are high, manufacturers have proposed spacing out costs over time. Governments and insurers are still trying to figure out how to pay for the treatments and facing uncertainty over long-term benefits and safety.

Bluebird, which expects approval in the U.S. in 2020, said earlier this year that it plans to make as much as 80% of the therapy’s cost dependent on its performance over a period of up to five years. The drugmaker said it will carry out a country-by-country effort to gain reimbursement for the therapy.

In an interview in March, Bluebird Chief Executive Officer Nick Leschly signaled that getting countries to agree to pay for the therapy could take some time. European nations may grant coverage over six months to two years, with Germany possibly coming first, he said at the time. The company has a manufacturing site in Munich and has arranged nine treatment centers in Europe, including four in Italy and three in Germany.

Novartis’s Zolgensma, the first multimillion-dollar drug in the U.S., is approved to treat children under two years old who have a severe illness called spinal muscular atrophy. The company has also said it plans to offer refunds to patients when the treatment fails to work.

To contact the reporter on this story: James Paton in London at jpaton4@bloomberg.net

To contact the editors responsible for this story: Eric Pfanner at epfanner1@bloomberg.net, John Lauerman

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