Investigation of product derived lymphoma following infusion of piggyBac modified CD19 chimeric antigen receptor T-cells.

We performed a Phase I clinical trial of donor derived CD19-specific chimeric antigen receptor T-cells (CAR T-cells) for B-cell malignancy that relapsed or persisted after matched related allogeneic hemopoietic stem cell transplant. To overcome the cost and transgene capacity limitations of traditional viral vectors, CAR T-cells were produced using the piggyBac transposon system of genetic modification. Following CAR T-cell infusion, one patient developed a gradually enlarging retroperitoneal tumor due to a CAR expressing CD4+ T-cell lymphoma. Screening of other patients led to the detection of a second CAR T-cell tumor in thoracic para-aortic lymph nodes in an asymptomatic patient. Analysis of the first lymphoma showed a high transgene copy number, but no insertion into typical oncogenes. There were also structural changes such as altered genomic copy number and point mutations unrelated to the insertion sites. Transcriptome analysis showed transgene promoter driven upregulation of transcription of surrounding regions despite insulator sequences surrounding the transgene. However, marked global changes in transcription predominantly correlated with gene copy number rather than insertion sites. In both patients, the CAR T-cell derived lymphoma progressed and one patient died. We describe the first two cases of malignant lymphoma derived from CAR gene modified T-cells. Although CAR T-cells have an enviable record of safety to date, our results emphasize the need for caution and regular follow up of CAR T recipients, especially when novel methods of gene transfer are used to create genetically modified immune therapies. The trial was registered at www.anzctr.org.au as ACTRN12617001579381.