Effects of Prior Exposure to Tec Kinase(BTK/ITK) Inhibitors on Kte-X19 Products
Authors: Scarfò Irene , Gallagher Kathleen M.E. , Leick Mark B. , Kann Michael C. , Budka Justin , Sowrirajan Bharat , Nguyen Kim , Shen Rhine R. , Bot Adrian , Maus Marcela V. 
Published: November 2021

Abstract
Introduction:
Frequent and durable responses were recently reported in relapsed or refractory (R/R) mantle cell lymphoma (MCL) patients treated with KTE-X19, an autologous CD19-targeted chimeric antigen receptor-engineered T-cell (CAR-T) product (Wang et al. N Engl J Med. 2020). Most patients enrolled had received at least one line of Tec kinase inhibitor prior to KTE-X19 manufacturing, either in the form of ibrutinib, a Bruton's tyrosine kinase (BTK) and Inducible T cell kinase (ITK) inhibitor, or acalabrutinib, a more selective BTK inhibitor. Pharmacokinetic expansion of KTE-X19 was higher in ibrutinib-treated patients relative to acalabrutinib-treated patients. We previously showed that prolonged exposure to ibrutinib enhanced T cell effector function and proliferation in patients with CLL (Fraietta et al, Blood, 2016). To assess the impact of Tec kinase inhibitor on KTE-X19 products and downstream clinical outcomes, we examined the phenotype, transcriptional profile and cytokine production of KTE-X19 infusion products and post-infusion lymphocytes from patients with R/R MCL treated on the Zuma-2 study.
Study Design and Methods:
We evaluated biospecimens from MCL patients who enrolled on the Zuma-2 clinical trial (NCT02601313) and who were previously treated with ibrutinib (n=14) or acalabrutinib (n=6). Samples analyzed consisted of KTE-X19 CAR T products and peripheral blood mononuclear cells (PBMC) collected 7 days after infusion. Lymphocytes were assessed for CAR expression, T cell phenotype, transcriptional profile and cytokine production. In addition, CAR T cell phenotypes and cytokines were profiled following co-culture of KTE-X19 with CD19 + Toledo cells (DLBCL).
Results:
Flow cytometric analysis of KTE-X19 demonstrated similar distributions of CD4+ and CD8+ T cells and comparable frequencies of central and effector memory populations in the CAR+ T cells derived from patients with prior exposure to ibrutinib vs. acalabrutinib. T helper subset analysis trended towards enrichment of Th1/Th17 populations within the CAR+ CD4+ cells of the ibrutinib cohort. This finding was further supported by transcriptional profiling of sorted CAR+ T cells from infusion products, where Th1/Th17, Jak/STAT and activation-related genes were enriched in the cohort with prior ibrutinib exposure. In addition, the Th1 phenotype was more frequent in PBMC of ibrutinib-exposed patients (8/14) compared to acalabrutinib-exposed patients (1/4). Interestingly, a shift from a central memory-dominant product towards an effector memory phenotype was observed in peripheral CD4+ and CD8+ CAR T cells in the ibrutinib cohort, whereas acalabrutinib post-infusion CAR T cells maintained a central memory phenotype. In vitro stimulation of KTE-X19 CAR-T infusion products with tumor cells resulted in a significant enrichment of the Th1 population in patients who had received ibrutinib compared to those that received acalabrutinib (p=0.0058). Following stimulation, CAR-T cells from the acalabrutinib cohort produced higher levels of Th2 cytokines, including IL-4, IL-5, and IL-13 as well as GM-CSF compared to the ibrutinib cohort.
Conclusions:
Analysis of KTE-X19 infusion products and day 7 post-infusion PBMC demonstrated that CAR T cells from patients with prior ibrutinib exposure have a Th1 predominant phenotype, suggesting that ibrutinib but not acalabrutinib promotes Th1 differentiation and effector function, potentially through the inhibition of ITK. Furthermore, our data suggest that inhibition of non-BTK targets such as ITK may play a role in driving a Th17 phenotype. Prior exposure to ibrutinib may increase CAR T cell effector function to a greater extent than exposure to acalabrutinib to enhance clinical outcome in patients with MCL.

Disclosures
Budka: Kite Pharma: Current Employment. Sowrirajan: Kite Pharma: Current Employment. Nguyen: Kite Pharma: Current Employment. Shen: Gilead Sciences: Current equity holder in publicly-traded company; Kite, a Gilead Company: Current Employment, Other: Leadership role, Patents & Royalties; Atara: Current Employment, Current equity holder in publicly-traded company, Other: Leadership role, Patents & Royalties. Bot: Kite, a Gilead Company: Current Employment; Gilead Sciences: Consultancy, Current equity holder in publicly-traded company, Other: Travel support. Maus: Agenus: Consultancy; Arcellx: Consultancy; Astellas: Consultancy; AstraZeneca: Consultancy; Atara: Consultancy; Bayer: Consultancy; BMS: Consultancy; Cabaletta Bio (SAB): Consultancy; CRISPR therapeutics: Consultancy; In8bio (SAB): Consultancy; Intellia: Consultancy; GSK: Consultancy; Kite Pharma: Consultancy, Research Funding; Micromedicine: Consultancy, Current holder of stock options in a privately-held company; Novartis: Consultancy; Tmunity: Consultancy; Torque: Consultancy, Current holder of stock options in a privately-held company; WindMIL: Consultancy; Adaptimmune: Consultancy; tcr2: Consultancy, Divested equity in a private or publicly-traded company in the past 24 months; century: Current equity holder in publicly-traded company; ichnos biosciences: Consultancy, Current holder of stock options in a privately-held company.