A phase I trial of CD19-targeted EGFRt/19-28z/4-1BBL armored chimeric antigen receptor (CAR) modified T cells in patients with relapsed or refractory chronic lymphocytic leukemia

TPS7568 Background: Despite the recent progress in the therapy of CLL with BTK, PI3Kδ, and BCL2 inhibitors, CLL remains incurable and patients with high-risk disease features (i.e. del17p, complex karyotype) and patients whose disease progress after treatment with the above targeted agents continue to have extremely poor prognosis. CD19-specific chimeric antigen receptor (CAR) T cell therapy with various 2nd generation CARs (19-28z or 19-41BBz) have demonstrated anti-tumor efficacy in CLL but the complete response (CR) rates in CLL have been suboptimal (20-45%) compared to CR rates in ALL (80-90%). The suboptimal activity of the current 2nd generation CAR T cells can be due to the inhibitory tumor microenvironment (TM) of CLL. We believe one approach to over the hostile TM is through the use of CD19-CAR T cells further modified to express a second costimulatory ligand, 4-1BBL. A binding of 4-1BBL to its cognate receptor enhances T cell proliferation, IL-2 secretion, and survival and cytolytic activity of the T cells compared to 19-28z. 19-41BBz and 1928BBz (Zhao Z et al. Cancer Cell 2015;28:415-428). Methods: This phase I dose escalating trial is a single-center clinical trial (MSKCC) to study the safety and efficacy of autologous EGFRt/19-28z/4-1BBL+ CAR T cells in patients with relapsed CLL. Given the concern for potential systemic toxicity the vector includes a "safety switch" in the form of a gene for the expression of truncated form of human epidermal growth factor receptor (EGFRt). Patients with relapsed CLL are eligible for the trial. Patients will receive conditioning chemotherapy of cyclophosphamide followed by escalating doses of CAR T cells (1x105 – 3x106 CAR T cells/kg). The primary endpoint is safety and maximum tolerated doses of the CAR T ells. Secondary objectives include response assessment by iwCLL criteria. The comprehensive treatment algorithms for CRS and neurotoxicity are based on our CAR T cell experience in other studies. The study will begin enrollment in February 2017 and enroll up to 30 patients. Clinical trial information: Pending.