Monday could be a big day for Bluebird Bio (NasdaqGS: BLUE), shares of which are up more than sevenfold in the past year, after the company said on Saturday that a French teenager with severe sickle cell disease responded positively to Bluebird Bio’s LentiGlobin BB305 product.

“The proportion of anti-sickling hemoglobin being produced by the first-ever patient with severe SCD treated with gene therapy (Subject 1204) is rising steadily and accounted for 45% of all hemoglobin production (40% HbAT87Q + 5% HbF) at the patient’s six-month visit post-drug product infusion; this is above the 30% threshold expected to potentially achieve a disease-modifying clinical effect,” the company said in a statement.

Bluebird Bio added: “As of May 2015, Subject 1204 had been free of transfusions for more than three months without complications or hospitalizations for SCD-related events post-transplant, and with improvement in hemolysis markers.”

One patient is just one patient, but those that suffer from severe SCD usually do not show improvement with treatment, indicating markets could react favorably to the Bluebird data. That could be good news for some exchange traded funds that hold the stock, which has nearly doubled this year.

A good ETF starting point for Bluebird Bio is the ALPS Medical Breakthroughs ETF (NYSEArca: SBIO), which focuses on small- and mid-cap companies that have one or more drugs in either Phase II or Phase III U.S. FDA clinical trials. [Biotech ETFs are Scorching Hot]

SBIO, debuted on December 31, is already home to $91 million in assets after surging 38.5%, making it one this year’s top-performing sector funds. The ETF had a 5% weight to Bluebird as of June 12, making the stock the fund’s second-largest holding.

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