GlaxoSmithKline's talk of leaving rare diseases—amid slow Strimvelis sales—highlights challenges in the field

GSK on Wednesday announced it's exploring a sale of its rare disease meds.

GlaxoSmithKline’s decision to explore a sale for its rare disease portfolio offers an opportunity for those who may be eyeing the field, but it's also another warning sign that drugmakers can struggle to find a market for their expensive gene therapies. And with Novartis and Kite Pharma on the verge of approvals for cancer treatments of that ilk—likely to be quite pricey—more companies will face similar challenges.

After conducting a review of its rare disease meds, GSK on Wednesday disclosed it is “considering options for future ownership of these assets.” The group includes Strimvelis, a $665,000 treatment for the rare immune system disorder ADA-SCID, and two other programs in development. 

In a statement to FiercePharma, GSK spokeswoman Mary Anne Rhyne said that while the drugmaker has “been heavily invested in this area, we believe there is someone else who can best ensure the commercial availability of these medicines for patients.” GSK isn't leaving "cell and gene therapy R&D, but will focus on oncology and more common indications," Rhyne added.

"Our immediate priorities are to focus on meeting our obligations to patients," she said in a statement. "Our intention is to ensure that these medicines are given the best possible chance of successful development and commercialization."

RELATED: GlaxoSmithKline stops development of 30 pipeline prospects, mulls sale of rare disease unit

So far, just two patients have received treatment with Strimvelis and two more are lined up to receive the gene therapy later this year. The med won European approval last May to treat a disease that affects about 15 children per year there.

GSK’s decision follows uniQure’s announcement earlier this year it will stop selling Glybera after that gene therapy’s marketing authorization expires in October.

Priced at a staggering $1-million-plus, Glybera won a green light in 2012 in Europe to treat lipoprotein lipase deficiency. But uniQure said in April the med has seen “extremely limited” use since its introduction and that the company doesn’t see demand getting better. The biotech is instead planning to focus on programs for hemophilia B and Huntington’s disease, as well as a cardiovascular collaboration with Bristol-Myers Squibb.

Strimvelis has its own challenges, including cost. At $665,000, it’s among the most expensive therapies in the world. But like other gene therapies, it’s also a cure, in this case for severe immunodeficiency stemming from a lack of adenosine deaminase (ADA-SCID), rather than an ongoing treatment as other rare disease drugs are.

RELATED: With its launch fizzling out, UniQure gives up on $1M+ gene therapy Glybera

GSK set up pay-for-performance deals in some markets to deal with the pricing issue. “The drug has to deliver what you say or we don’t pay,” Luca Pani, director general of the European Medicines Agency, said of its own arrangement with GSK last year. “If it does not work, they will return the money.”

When approved, the company said its drug would be distributed only in Milan, Italy, which means families had to travel for treatment, and the Italian health authorities’ arrangement with GSK covers all European patients, MIT Tech Review said at the time. Strimvelis was developed in partnership with Italy’s San Raffaele Telethon Institute for Gene Therapy.

On the other side of the rare disease coin, Biogen is seeing quite different results for its new super pricey Spinraza to treat spinal muscular atrophy. The drug costs $750,000 for the first year of treatment and blew past analyst sales projections in second-quarter results released Tuesday. After a U.S. approval late last year, the drug turned in $203 million in sales for the quarter, far surpassing the $69 million Street estimate.

RELATED: Payer buy-in for Biogen's Spinraza gives big biotech major revenue boost

Some market-watchers worried the med’s price would cause payers to put up barriers, but those fears at least for now seem to be unwarranted. Many top payers cover the med for SMA types 1 to 3, while two groups limit its use to type 1, according to a recent note from Bernstein analyst Ronny Gal.

To help allay payer concerns, Biogen has said it’s working to ink value-based deals, too. CEO Michel Vounatsos said on Tuesday the company has inked four deals so far and is continuing to develop those arrangements.