LentiGlobin Looks Promising On Sickle Cell For bluebird bio, Says Analyst

November 19, 2014

By Riley McDermid, BioSpace.com Breaking News Sr. Editor

Gene therapy company bluebird bio has a winner on its hands with sickle cell anemia drug LentiGlobin and has achieved “robust” proof of concept for the therapy so far, said Joshua Schimmer, a biotech analyst with Piper Jaffray, Wednesday.

“Yesterday we hosted a call with a hemoglobinopathy specialist. Based on this and our assessment of the data reported for LentiGlobin in beta-thal, we conclude the product has achieved robust proof of concept which is also likely to translate into success in sickle cell anemia,” wrote Schimmer in a note to investors.

So far, bluebird has reported results from three patients with the less severe zero/E form of beta-thal, including one patient who has not yet reached steady state Hb levels but seems to be tracking at a slower rate of improvement, said Schimmer.

The first two patients who achieved transfusion independence had a vector copy number x dose of cells above 10 x 10^6/kg 'genes.’ One patient reached 13.4 x 10^6/kg 'genes,' the other reached 28.6 x 10^6/kg 'genes.' The lagging patient was well below at only 6.8 x 10^6/kg 'genes.'

“Obviously there are some limitations to our calculations but from a high level perspective it should help inform expectations,” said Schimmer Projecting the next patients is also doable, said Schimmer. Two patients have not yet reached a measurement of Hb response. One zero/E patient received only 3.8 x 10^6/kg 'genes' while the zero/zero patient we calculate to have received 18.5 x 10^6/kg 'genes'.

“The latter should have a robust response and reach transfusion independence, we suspect, because even modest residual contribution from the native cells should be enough to sustain a target Hb >10,” he said. “This would be an important positive for BLUE.”

Overall, the data analysts have seen “seems adequate and bodes well” for patients with sickle cell anemia, said Piper Jaffray. LentiGlobin does not need to hit 100 percent transfusion independence to be commercially viable, the note stressed.

“We believe if the response rate to date holds up, the product will have a meaningful role in the treatment armamentarium for beta-thal,” wrote Schimmer.

“Furthermore, the specialist indicated that diluting the S (sickle) gene to 30 percent in sickle cell patients using transfusions can halt sickling and for some even dilution to 50 percent can halt. The first two patients treated so far have reached corrected Hb levels of 70 percent and 62 percent respectively. At least over the short term, we suspect 3/5 patients will be above a 50 percent dilution threshold.”