116 Applications of the ΔtBIG method of cooling rate quantification to cell therapy cryopreservation under GMP compliance

Abstract

Cryopreservation is a commonly adopted method for preserving allogeneic cell therapies through long-term storage and distribution to end-users. For clinical and eventually commercial manufacturing of these products, the cooling leg of the cryopreservation cycle is performed within a manufacturing environment that is regulated for Good Manufacturing Practices (GMP). To comply with GMP, the cooling process is held to high standards for process characterization and control, including defining critical process parameters, specifying acceptable ranges for those parameters, and verifying that each parameter is consistently controlled to within its specified range during normal operation. For cell products of defined composition, cooling rate is the primary critical process parameter that drives the performance of the cooling process. To successfully describe product cooling, cooling rate should be quantified in a specific and relevant manner that is independent of scale and freezer model, and enables measurement of multiple unit containers across a freezer load of interest. To support process development, engineering, scale-up and validation of the controlled-rate freezing step for CLT-008, an “off-the-shelf” cryopreserved myeloid progenitor cell therapy for neutropenia, we have defined a term which quantifies product cooling rate and serves as the primary critical process parameter linking product cooling to recovery of function. This cooling rate term, Δt BIG , represents the time required for bulk ice growth and is defined as the time difference between product nucleation and achieving −20 °C: Δ t BIG = t - 20 - t n ′ . Δt BIG has been successfully applied to internal and external monitoring of cryobags and vials to determine cooling rates of multiple individual product containers across controlled-rate freezer loads. Δt BIG distributions have served as the basis for load configuration and cooling program engineering as well as a means of setting acceptable ranges for performance qualification of GMP manufacturing freezes. The application of this cooling rate quantification method to cell cryopreservation development and GMP manufacturing is described using CLT-008 as a case study. Source of funding: Biomedical Advanced Research and Development Authority (BARDA). Conflict of interest: Cellerant is developing CLT-008 as a commercial therapy for neutropenia. dfrey@cellerant.com