Role of Cell Therapy Product Characteristics in Patient Response to TAK-940 (CD19(T2)28z1xx Chimeric Antigen Receptor (CAR) T): Biomarker Analyses from a Phase I Study in Adult Patients with Relapsed or Refractory B-Cell Malignancies

TAK-940 (CD19(T2)28z1XX Chimeric Antigen Receptor (CAR) T) is an autologous CD19 CAR T cell therapy utilizing an optimized 1XX signaling domain substituting for the natural CD3ζ immunoreceptor tyrosine-based activation motifs. This 1XX design extends the functional persistence of CAR T cells with increased potency in mice (Feucht J et al. Nat Med 2019). TAK-940 is being evaluated in a Ph1 trial in patients with Relapsed or Refractory B-cell malignancies (NCT04464200) with demonstrated early signals of clinical efficacy (Park J et al. ASH 2022). The present study aims to provide a better understanding of the clinical performance of CD19(T2)28z1XX CAR T cells by in depth characterization of the cellular products and patient samples from this Ph1 trial.

A total of 28 subjects were enrolled and treated in the dose escalation and expansion cohorts of the Ph1 trial. Responses were observed across all dose levels (25x10⁶ to 200x10⁶ CAR T cells), achieving ORR 82%, CR 71%. Immunophenotyping by flow cytometry was conducted on patient apheresis material, un-transduced cells, transduced cellular drug product and peripheral blood samples from infused subjects. Circulating cytokine profiling was performed on patient serum samples collected pre and post treatment with TAK-940.

In the transduced cellular drug products, CAR+ and CAR- CD8+ central memory and transitional memory T cells were more abundant than naïve, stem cell memory or terminal effector populations. This elevation in central and transitional memory T cells seen in the drug product was not observed in the patient apheresis material, indicating that this effect is likely driven by the production process. CD57 and TIM3 expression in both CD4+ and CD8+ CAR+ T cells in the drug product showed a positive association with clinical response, while CTLA4 or LAG3 expression independently was negatively associated with response. The drug product also contained low numbers of dysregulated/exhausted T cells, with no observable difference between responders and non-responders. Interestingly, in the starting apheresis material, increased expression of TIM3 as well as decreased expression of either LAG3 or KLRG1 in CD8 T cells, independently associated with responses. Current analysis is based on associations with complete response. Additional analyses to be reported will include associations with ORR and durability of responses. These findings suggest potential utility of these T cell markers in predicting patient response and warrant evaluation in a larger population.

Although CD57 expression has been associated with a senescent phenotype, we hypothesize that the observed increase in CD57 expression in CD4+ and CD8+ CAR+ T cells in the product may indicate higher cytotoxic potential of those cells. Increase in CD57+ CAR+ T cell subsets has been previously associated with durable CRs in large B cell lymphoma patients treated with axi-cel (Good Z et al. Nat Med 2022). Additional analyses to further characterize the CD57+ cell populations and establish their role in clinical responses to CAR T cell therapy with the 1XX CAR design are in progress.

The increased expression of CD57 and the activation marker TIM3, and decreased expression of inhibitory receptors CTLA4 and LAG3 in the drug product from responders, together with the robust clinical responses observed with doses as low as 25x10⁶ CAR T cells, suggest that the product consists of highly potent T cells, in accordance with the preclinical results obtained with the 1XX CAR. Low levels of circulating cytokines were observed following treatment with TAK-940, including IFNg, IL-6, IL-10, indicating a safe and tolerable CAR T product consistent with the observed clinical safety profile of TAK-940. Correlative analysis of T cell immunophenotypes observed in the product to clinical parameters including durability of responses, metabolic tumor volume/tumor burden, and induction of cytokines and chemokines is ongoing and will be reported. This will further contribute to our understanding of CD19 CAR T cells endowed with a 1XX signaling domain and potentially support the identification of product and/or apheresis biomarkers that may predict patient response.