T cell therapy with L1-CAM-targeting chimeric antigen receptors (CAR) as immune therapy for neuroblastoma patients after haploidentical stem cell transplantation.
Final Report Abstract
Despite therapeutic efficacy of chimeric antigen receptor (CAR) redirected T cell immunotherapy in the setting of leukemia and lymphoma, similar clinical responses in the setting of solid tumors, such as neuroblastoma remains to be seen. In my project, I used a CAR targeting CE7, an epitope on CD171 (L1CAM). CD171 was initially found to be overexpressed in neuroblastoma and more recently, correlation of CD171 expression with tumor progression and metastasis in several other cancer entities has been shown. I designed a series of CD171-specific CARs with varying extracellular spacer lengths and cytoplasmic signaling domains that, when expressed by T cells, displayed differential magnitudes of tumor cell cytolysis and cytokine secretion based on in vitro assays. Unexpectedly, the extracellular long spacer variant of the 2nd generation (G) 4-1BBzeta CAR that displayed the highest in vitro activity performed the worst in vivo. Using an in vitro assay system that recapitulates recursive CAR triggering by repetitive tumor exposure, we observed that a high performance long spacer CAR upregulated FasL to a greater extent resulting in exaggerated activation induced cell death (AICD). Moreover, the 4-1BBzeta short spacer CAR that under performed in vitro, but exhibited the most potent anti-tumor effect in vivo, when converted to a 3rd G CAR, lost therapeutic potency in vivo. This was concurrent with acquisition of augmented AICD. In conclusion, we showed that extracellular spacer length and cytoplasmic signaling domain(s) have an enormous impact on CAR T cell function. As such, our data suggests that CAR development and design requires therefore careful attention. Further, highest CAR output in single pass T cell assays did not determine the optimal CAR for clinical use. Our new CAR-T cell stress test revealed new and potentially clinical relevant parameters for inspection in the development of CAR T cell immunotherapy. Together with Julie Park, I wrote a clinical protocol about using CD171-CAR-T cells for treatment of neuroblastoma patients. This phase I, open-label, non-randomized study will enroll children with recurrent or primary refractory neuroblastoma to examine the safety and feasibility of administering autologous, peripheral blood-derived T cells expressing a CD171-specific CAR. The primary objectives of this study will be the feasibility of deriving the cell product, the safety of the T cell product infusion, and to determine the maximum tolerated dose and dose limiting toxicities of 2nd and 3rd G CAR-T cells and to describe the full toxicity profile. The FDA approved the IND and the first patients were enrolled in January 2015. Using apheresis products from neuroblastoma patients previously harvested during initial therapy as possible CAR T cell source is currently under evaluation and might be part of a subsequent trial.
Publications
- Functional tuning of CARs reveals signaling threshold above which CD8+ CTL antitumor potency is attenuated due to cell Fas-FasL dependent AICD. Cancer Immunol Res, 2015 Jan 9
Künkele, A., et al.
(See online at https://doi.org/10.1158/2326-6066.CIR-14-0200)
