Enhancing Fas-mediated Bystander Killing of Follicular Lymphoma to prevent post-immunotherapy antigen escape.

Follicular lymphoma (FL) is generally considered incurable, however, newer T-cell mediated therapies including bispecific Abs (bsAbs) and CAR-T cells induce complete remissions in a majority of FL patients and show early plateaus in remission curves suggesting that -in 2022- the goal of FL therapy should be durable remission or cure. However, T-cell mediated therapies share a common limitation: tumoral antigen (Ag) escape; rare Ag– cells in heterogeneous tumors evade attack and lead to relapse. After anti-CD19 CAR-T therapy orCD3xCD20 bsAbs a large proportion of relapsing patients have developed CD19– or CD20– tumors respectively. One solution to treat Ag escape -re-targeting a distinct Ag (e.g. anti-CD22 CAR-T)- may be limited by i) concurrent loss of multiple Ag and ii) lack of tumor-specific, homogeneously expressed Ag candidates.

Instead of attempting to treat Ag escape, we recently suggested an innovative approach to prevent it, by enhancing geographically-localized T cell ‘Bystander Killing’. Specifically, we identified the critical role of FasL-Fas-mediated On-Target and Bystander Killing using a 2400-target CRISPR screen and validated this finding in murine and human models of transgenic TCR, CAR-T, and bsAb-directed T cells. We provided evidence from a large anti-CD19 CAR-T clinical trial that constitutive Bystander Killing may already be, partly, preventing Ag escape, by demonstrating that tumoral Fas-expression is an even greater predictor of patients’ survival than CD19-expression itself. Most importantly, we showed that inhibiting Fas regulators e.g. Bcl2, IAP, and HDAC family members, enhanced Bystander Killing.

The proposed Project will i) use cryopreserved excisional FL biopsies from three prior IITs and flow-cytometric-sorting, followed by scRNAseq/CITEseq to characterize both rare CD19– and CD20– primary FL cells (focused on Fas and Fas-regulators e.g. KMT2D, Bcl-2, IAP, and HDAC family members) as well as bulk RNAseq of sorted intratumoral (or autologous matched-PBMC) T cells upon ex vivo bsAb treatment (focused on FasL and FasL-regulators e.g. ADAM10, MMP7, TGFβ), ii) demonstrate that bsAb-activated T cells can mediate Bystander Killing in Ag– FL cells, and iii) determine whether inhibition of known or newly-discovered regulators of Fas or FasL can potentiate Bystander Killing of Ag– FL cells, including KDM5i modulation of KMT2D-mut FL cells.

Name of applicants and institution
PI: Joshua Brody M.D.
Co-investigator: David Dominguez-Sola, M.D., Ph.D.
Co-investigator: Miriam Merad M.D., Ph.D.

Icahn School of Medicine at Mount Sinai