A phase I clinical trial using armored GPC3 CAR T cells for children with relapsed/refractory liver tumors.

Abstract

TPS2647 Background: CAR T therapies have been successful against hematologic malignancies, but have benefited only a handful of patients with solid cancers. Glypican 3 (GPC3) is an attractive immunotherapeutic target due to its preferential expression on multiple pediatric and adult solid cancers and lack of expression on non-malignant tissues. GPC3-CAR T cells were tested preclinically and inclusion of the 4-1BB costimulatory endodomain with IL-15 and IL-21 co-expression enabled CAR T cells to expand and persist the most in vitro and in vivo and led to robust antitumor activity in vivo. We are now testing GPC3-CAR T cells with IL15 and IL-21 for the first time in children with relapsed/refractory liver tumors. Methods: In this Phase 1 trial (GAP, NCT02932956), we are evaluating patients in 3 cohorts: 1) GPC3-CAR alone; 2) GPC3-CAR and IL-15; 3) GPC3-CAR with IL-15 and IL-21. We will 1) define the safety and establish the Recommended Phase 2 Dose (RP2D) of GPC3-CAR T cells co-expressing IL-15 and IL-21; 2) determine persistence and anti-tumor activity of GPC3-CAR T cells; 3) examine changes in gene and protein expression in the tumor microenvironment associated with potential immune escape mechanisms. Inclusion criteria are the following: age ≤18; histology proven, GPC3-positive tumor; life expectancy>12 weeks; Child-Pugh-Turcotte score<7; serum AST<5 times ULN; total bilirubin<3 times ULN for age; INR ≤1.7; absolute neutrophil count>500/μl; platelet count>20,000/μl; Hgb≥9.0 g/dl. Toxicity will be monitored using the Common Terminology Criteria of Adverse Events v4. The RP2D will be determined by the standard 3+3 dose escalation method using 5 dose levels. Persistence will be quantified using RT-PCR and flow cytometry. Antitumor activity will be defined by 3D imaging using RECIST 1.1 criteria and the immune-related response criteria. Immune-escape will be examined using single cell RNA sequencing and imaging of paraffin-embedded tissues using codetection by indexing to evaluate candidate proteins. Data will be analyzed via descriptive statistics. Cohort 1 of this study is now open for enrollment. Clinical trial information: NCT02932956.

Rational design of chimeric antigen receptor T cells against glypican 3 decouples toxicity from therapeutic efficacy

“…Because GPC3-1 and GPC3-2 share a V H sequence, they were expected to maintain a shared epitope for GPC3 binding. Indeed, in competition assays, GPC3-1 and GPC3-2 effectively competed each other for GPC3 binding, confirming that they recognize a similar if not identical epitope, but they did not compete with another high-affinity antibody GPC3, GC33 [23] (Supplementary Fig. 1A and 1B).…”

“…To confirm that both GPC3-1 and GPC3-2 CARs support CAR-T cell function, we co-cultured Jurkat cells transduced with GPC3-1 or GPC3-2 CARs with the GPC3expressing HCC line, Hep3B. Both GPC3-1 and GPC3-2 CARs drove specific upregulation of the activation marker CD69 in co-culture with Hep3B cells, similar to a positive control CAR using the GC33 scFV [23]. GPC3-2 drove slightly stronger activation than GPC3-1 in this assay, possibly owing to the increased avidity (Fig 1D).…”

Novel Cellular Therapies for Hepatocellular Carcinoma

“…Whilst these response rates are disappointing, the toxicity profile was broadly tolerable, and this study has provided the foundation for further development of 'optimised' GPC3-CAR-T approaches. To this end, 'armoured' GPC3-CAR-T designs, with engineered modules for 41BBL and IL-15/IL-21 (NCT02932956) [75], combinatorial approaches using concurrent TKIs or IPIs (NCT03980288), and targeted delivery via hepatic artery infusion (NCT03993743) are all under investigation.…”

Beyond direct killing—novel cellular immunotherapeutic strategies to reshape the tumor microenvironment

“…"Armored" CARs in contrast constitutively express these cytokines for permanent enhanced cellular function [65,66]. Though not exhaustively listed due to the magnitude of research, examples of cytokines targeted for coexpression on these cellular therapies include IL-7 [67], IL-12 [66,[68][69][70], IL-15 [71][72][73], IL-18 [74][75][76], IL-21 [77,78], IL-23 [79], IL-24 [80], IL-33 [81], and IL-36 g [82]. These cytokines have a range of effects that include signaling T-cell survival, improving T-cell proliferation, and promoting their differentiation into further subtypes.…”