Adoptive cell therapies like CAR-T have proven effective, potentially curative treatments for certain blood cancers, and the technology is being applied to autoimmune diseases, including inflammatory bowel disease (IBD), rheumatoid arthritis (RA), multiple sclerosis (MS), and systemic lupus erythematosus (SLE). Given these modalities involve extracting a patient’s own cells, engineering and expanding them outside the body into a safe and reproducible “living drug” to be readministered to the patient, an entirely new pharmaceutical science referred to as process development has evolved to manage, optimize, and ensure the quality of the manufacturing process.

Process development scientists labor to emulate the clinical manufacturing of the cell therapy product at every stage of the drug pipeline. The immune cells engineered into disease-fighting drugs often are in low circulating abundance. For example, regulatory T cells (Tregs; e.g., CD4+CD25+FoxP3+ cells), a popular target for autoimmune cell therapy, comprise only ~1% of peripheral T cells. Isolating Tregs by apheresis is needed as a first step before fluorescence-assisted cell sorting.¹ Therefore, process development teams often use lymphocyte-enriched apheresis products from human donors (a.k.a. “leukopaks”) as surrogates for establishing process development parameters in anticipation of the “real thing” coming from patients in clinical trials.

Most leukopaks come from healthy donors; however, patients with autoimmune conditions typically present with different immune cell profiles than healthy-matched controls (Figure 1). Peripheral blood immunophenotype distributions can distinguish Crohn’s disease and ulcerative colitis patients², RA and Spondyloarthritis at early stages of disease³, and correlate with disease progression and treatment response in MS⁴. Thus, access to leukopaks from patients with confirmed disease can provide a more accurate representation of the lymphocyte apheresis material from patients receiving the autologous treatment.