Determinants of response and resistance to CD19 chimeric antigen receptor (CAR) T cell therapy of chronic lymphocytic leukemia

Abstract

Tolerance to self-antigens prevents the elimination of cancer by the immune system1,2. We used synthetic chimeric antigen receptors (CARs) to overcome immunological tolerance and mediate tumor rejection in patients with chronic lymphocytic leukemia (CLL). Remission was induced in a subset of subjects, but most did not respond. Comprehensive assessment of patient-derived CAR T cells to identify mechanisms of therapeutic success and failure has not been explored. We performed genomic, phenotypic and functional evaluations to identify determinants of response. Transcriptomic profiling revealed that CAR T cells from complete-responding patients with CLL were enriched in memory-related genes, including IL-6/STAT3 signatures, whereas T cells from nonresponders upregulated programs involved in effector differentiation, glycolysis, exhaustion and apoptosis. Sustained remission was associated with an elevated frequency of CD27+CD45RO- CD8+ T cells before CAR T cell generation, and these lymphocytes possessed memory-like characteristics. Highly functional CAR T cells from patients produced STAT3-related cytokines, and serum IL-6 correlated with CAR T cell expansion. IL-6/STAT3 blockade diminished CAR T cell proliferation. Furthermore, a mechanistically relevant population of CD27+PD-1CD8+ CAR T cells expressing high levels of the IL-6 receptor predicts therapeutic response and is responsible for tumor control. These findings uncover new features of CAR T cell biology and underscore the potential of using pretreatment biomarkers of response to advance immunotherapies.

Mechanisms of resistance to CAR T cell therapy

“…Given the high response rates with CAR T cell therapy in patients with leukaemia and thus the small numbers of nonresponders, systematically evaluating and establishing parameters associated with a lack of responsiveness are difficult -particularly considering that the underlying causes are likely to be multifactorial and not fully attributable to product variables alone. In patients with CLL, however, among whom response rates have been substantially lower than those in patients with ALL or lymphoma, Fraietta et al 36 were able to identify favourable product characteristics, such as enrichment for IL-6-STAT3 signatures and an elevated frequency of CD29 + CD45RO − CD8 + T cells before CAR T cell generation. Furthermore, pre-infusion anti-CD19 CAR T cell products comprising polyfunctional T cells subsets, defined on the basis of cytokine and chemokine expression profiles, have been associated with an improved response in patients with lymphoma compared with products without such polyfunctional activity 57 .…”

“…Preferential manufacturing approaches involving these unique T cell populations are under development. In a study of patients with CLL who received an anti-CD19 CAR T cell product 36 , responders were found to have a CAR T cell population that was enriched for expression of memory-related genes, compared with that of nonresponders, and had higher numbers of CD27 + PD-1 − CD8 + CAR T cells expressing high levels of the IL-6 receptor, thus leading to better tumour control; this cell phenotype was more predictive of a response than other disease and patient characteristics 36 .…”

“…Similarly, specific integration of the CAR gene into the TCRα constant (TRAC) locus of the T cell genome using CRISPR-Cas9 editing machineries results in better antitumour responses than those observed with conventionally transduced CAR T cells in preclinical models 92 . Advances in gene-editing technologies 93 combined with enhanced understanding of determinants of CAR T cell potency and knowledge of determinants of therapeutic responsiveness will be crucial to the design of the next generation of CAR T cell technologies 36,94 . Thus, future directions to improve CAR persistence will rely heavily on understanding the optimal T cell biology in relation to CAR T cell functionality and subsequent optimization of CAR T cell design to promote persistence (when persistence is desired).…”

Inhibition of AKT signaling uncouples T cell differentiation from expansion for receptor-engineered adoptive immunotherapy

“…Similarly, infusion of less-differentiated T cell subsets that coexpress lymphoid homing markers like CD62L or costimulatory markers such as CD27 are associated with greater tumor regression (12)(13)(14). For example, in a recent clinical trial testing the antitumor efficacy of a second-generation anti-CD19 CAR containing a CD28 costimulatory domain, we found that the frequency of CD62L-expressing T central memory (T CM ) cells in the infusion product significantly correlated with the magnitude of CAR + cells in the peripheral blood (15).…”

Evolution of chimeric antigen receptor (CAR) T cell therapy: current status and future perspectives

“…For example, it was recently reported that CD19-targeting CAR-T cells created from inherently exhausted T cells isolated from chronic lymphoblastic leukemia (CLL) patients exhibit limited anticancer activity in patients owing to poor proliferative capacity (Fraietta et al 2018a). Whether such exhausted T cells can be reinvigorated through additional engineering is an important question for future CAR research (Ghoneim et al 2016).…”