Preclinical safety and efficacy testing of T-cell receptor (TCR)-based immunotherapies is challenging as these human-specific biologics require functioning human immune systems, and are therefore inadequately assessed in conventional animal models. Immune Mobilizing Monoclonal TCR Against Cancer (ImmTAC) molecules are bi-specific biologics that have shown significant therapeutic potency, but if misdirected, have the potential to cause serious toxicities.
In a recent paper in PLoS ONE, Harper et al. propose that a comprehensive but entirely in vitro set of assays will be adequate for preclinical efficacy and safety testing of TCR-based therapeutics. Proof of principle in vitro preclinical analyses were performed using four ImmTAC molecules. Among other tests, in vitro efficacy and specificity assays were performed on normal human and cancer cells to assess on-target and off-tumor activity; and in silico analyses of the ImmTAC peptide binding motifs were performed to identify possible cross-reactive peptides. In this study, the two most sensitive measurements of efficacy, namely target cell killing by cell lysis or cell apoptosis, were used to estimate safe starting doses for human trials. Kinetic analysis of apoptosis was measured over 52 hours using NucView® Caspase-3 Substrate and the IncuCyte® Live Cell Imaging System (Sartorius).
The authors conclude that the proposed assays, which comprise cellular and molecular assays using human tissues, can predict human responses, and should be considered for TCR-based therapies, and in other cases when relevant animal species are not available.