Bluebird Bio seeks to bring its gene therapies to European Market before the U.S., taking the advantages of a favorable regulatory pathway.

EMA's adaptive pathways process is appealing.

Andrew Obenshain, head of Bluebird Europe, told that the company is already in negotiations on possible regulatory filings with the EMA and the U.K.'s Medicine and Healthcare products Regulatory Agency (MHRA) .

The EMA's adaptive pathways process—which allows new therapies to be approved in stages based on stepwise collection of data—is a key part of that decision, as is the fact that the agency "works very closely with companies coming forward with new methodologies," said Morgan. And with Brexit looming, it makes sense to discuss these plans with the MHRA separately.

Two years ago, Bluebird—which targets severe genetic diseases and cancer—was hit hard when the NorthStar trial of lead therapy LentiGlobin failed to hit the mark in sickle cell disease and beta thalassemia, mainly because of variable patient responses to the treatment.

In a recent SEC filing, the company said that combined data from Northstar and other trials, including a follow-up Northstar-2 study, "could support the filing of a marketing authorization application in the EU" for transfusion-dependent thalassemia—provided they all meet the primary objective of freeing patients from the need for regular blood transfusions.

So far, no approved gene therapies have been in the U.S., while Europe has seen two approvals, namely for UniGene's Glybera (alipogene tiparvovec) for lipoprotein lipase deficiency and GlaxoSmithKline's Strimvelis for the ultrarare "bubble boy syndrome," or ADA-SCID.

Even getting approval is no guarantee of success, however. Glybera was taken off the market in April due to a lack of demand for the €1 million (around $1.2 million)-per-year therapy, with only one patient receiving it commercially since its launch in 2012.

GSK, meanwhile, has priced Strimvelis at a lower rate (around $650,000 a year) to try to encourage takeup, but hasn't given any updates and said last week it may put its rare disease unit up for sale. Rare disease head Carlo Russo moved to Italian biotech Genenta in January.