FDA lets blue­bird re­sume tri­als for sick­le cell gene ther­a­py af­ter can­cer scare, but big ques­tions linger over field

Blue­bird bio an­nounced that the FDA has lift­ed its holds on clin­i­cal tri­als for their gene ther­a­pies for sick­le dis­ease and be­ta-tha­lassemia, end­ing a 4-month saga that be­gan af­ter the biotech re­port­ed that two pa­tients had come down with can­cer and a can­cer-like con­di­tion.

Reg­u­la­tors were con­cerned that the cas­es may have been trig­gered by the virus blue­bird us­es to de­liv­er a healthy gene for he­mo­glo­bin in­to pa­tients with rare blood dis­or­ders, as had hap­pened in a 2004 gene ther­a­py tri­al that re­lied on a sim­i­lar virus. Blue­bird large­ly al­layed those con­cerns in March, when they re­leased a ge­net­ic analy­sis show­ing that the virus didn’t in­ter­fere with the pa­tient’s DNA in a way like­ly to trig­ger can­cer, but ex­perts say the cas­es have broad­ly raised con­cerns about the risks any of the more than half dozen of sick­le dis­ease gene ther­a­pies now in clin­i­cal de­vel­op­ment may pose.

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