LAUSR

Background & Aim Despite extensive usage of gene therapy medicinal products (GTMPs) in clinical studies and recent approval of CAR T cell therapy, little information has been made available on the precise molecular characterization and possible variations in terms of insert integrity and vector copy numbers of different GTMPs during the complete production chain. Within this context we characterize αβT cells Engineered to express a defined γδT cell receptor (TEGs) currently used in a first-in-human clinical study (NTR6541). Methods, Results & Conclusion Utilizing Targeted Locus Amplification in combination with Next Generation Sequencing for the vector producer clone and TEG001 products we report on 5 single nucleotide variants and 9 intact vector copies integrated in the producer clone. The vector copy number in TEG001 cells was on average a factor 0.72 (SD 0.11) below that of the producer cell clone. All nucleotide variants were transferred to TEG001, without having an effect on cellular proliferation during extensive in vitro culture. Based on an environmental risk assessment of the 5 nucleotide variants present in the non-coding viral region of the TEG001 insert, there was no altered environmental impact of TEG001 cells. We conclude that TEG001 cells do not have an increased risk for malignant transformation in vivo. In conclusion, we have reported an extensive molecular characterization of TEG001 transgene integrity that resulted in the approval a phase I clinical study which did not only allow to investigate the safety and tolerability of TEG001 in patients with relapsed/refractory acute myeloid leukemia, high-risk myelodysplastic syndrome, and relapsed/refractory multiple myeloma but also will provide a valuable framework for the molecular characterisation of future GTMPs.