TO THE EDITOR:

Tisagenlecleucel (CTL019; Kymriah) is an anti-CD19 genetically modified autologous T-cell therapy that is approved by the US Food and Drug Administration for treatment of relapsed/refractory pediatric and young adult B-cell acute lymphocytic leukemia (ALL) and adult diffuse large B-cell lymphoma (DLBCL).1,2  Before commercially manufactured CTL019 products can be labeled as tisagenlecleucel and released for administration to patients, a cryopreserved sentinel vial of manufactured cell product is thawed and tested for viability, using either Trypan blue exclusion or dual-fluorescence automated cell counting. For commercially manufactured CTL019, the viability specification for release of manufactured cells is at least 80% viability. In our and others’ experience, there is a proportion of CTL019 products that have viabilities lower than 80%. In the United States, CTL019 products with less than 80% viability currently require that patients enroll in an expanded access program...

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