Potency assays and biomarkers for cell-based advanced therapy medicinal products

Abstract

Advanced Therapy Medicinal Products (ATMPs) based on somatic cells expanded in vitro, with or without genetic modification, is a rapidly growing area of drug development, even more so following the marketing approval of several such products. ATMPs are produced according to Good Manufacturing Practice (GMP) in authorized laboratories. Potency assays are a fundamental aspect of the quality control of the end cell products and ideally could become useful biomarkers of efficacy in vivo. Here we summarize the state of the art with regard to potency assays used for the assessment of the quality of the major ATMPs used clinic settings. We also review the data available on biomarkers that may substitute more complex functional potency tests and predict the efficacy in vivo of these cell-based drugs.

Keywords: CAR (chimeric antigen receptor); T cell therapy; advanced therapy medicinal product (ATMP); biomarker; potency; stem cell; tissue regeneration.

Figure 1

Correlation between CAR expression and the cytotoxic potential of CARCIK-CD19 cells. CARCIK-CD19 cells expanded for clinical use of validation purposes, using the same GMP standard operating procedure, in 2 different Cell Factories (Center of Cellular Therapy “G. Lanzani, Bergamo and Laboratory of Cell and Gene Therapy Stefano Verri, Monza, Italy), in the context of common clinical trials (NCT03389035 and NCT05252403), were tested for percentage of CAR-CD19 expression and cytotoxic activity against the REH leukemic cell line, using the same assays conditions (N=60). Percentage CAR expression correlated significantly with percentage cytotoxicity (potency) (The Pearson correlation coefficient R=0,64, p<0.0001).

Figure 2

Donor MABs form myotubes in vitro. Spontaneous differentiation of donor MABs obtained from the medicinal product before infusion. 2x10⁵ MABs were plated on low-growth factor matrigel coated 3.5 cm Petri dish, in proliferation medium (Megacell). After an O/N incubation at 37°C, 5% CO₂, proliferation medium was replaced by differentiation medium (DMEM supplemented with 2% horse serum), and differentiation extended for 10 days. Cells were stained with anti-myosin heavy chain antibody and Dapi. Reprinted from (204).