674. Development of the Retroviral Vector Manufacturing Process for MM-TK Therapy

Abstract

The MM-TK Drug Product (DP) is a medicinal product used as adjunctive therapy in leukaemia patients undergoing stem cell transplantation. It is constituted of T lymphocytes genetically modified ex vivo with the γ retroviral vector SFCMM-3 Mut2 #48 encoding the HSV-TK Mut2 suicide gene and the cell surface marker ΔLNGFR. During clinical development, different improvements were introduced in retroviral vector (RVV) manufacturing in order to obtain simple and robust processes producing RVV with low level of impurities and high performance in lymphocyte transduction. Single-use bioreactors are currently replacing conventional bioreactors also for mammalian cell culture. They allow to increase biological and process safety by reducing cleaning and sterilization procedures and the risk of cross contaminations. In this context, we are currently evaluating different single-use, closed-system bioreactors for the manipulation of adherent packaging cell lines. A feasibility study is on-going, using a single-use bioreactor based on the 2D multi-tray stacks technology Xpantion system (Pall LifeSciences). This study explores the role of gas control on cell growth and its impact on the RVV quality attributes evaluating key metabolites, as glucose and lactate, and viral titer during cell expansion. In parallel a manufacturing process in 10-layers cell factories (CFs) has been developed and validated. The results obtained with the Am12/SFCMM-3 Mut2 #48 producer cell line grown up to 10 days in XP10 and in XP50 bioreactors showed an infectious viral titer on the reference cell line CEM A3.01, a transduction efficiency on T cells and an impurities level close to those obtained with the CFs.Process development and comparability data will be presented in more detail.