Cellectis Publishes Article in Frontiers in Immunology Unveiling Pre-Clinical Data on a Novel Treatment Paradigm for Successful CAR T Immunotherapy Against Stroma-rich Solid Tumors

Published on May 12, 2023

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May 12, 2023 - New York, NY – Cellectis (the “Company”) (Euronext Growth: ALCLS - NASDAQ: CLLS), a clinical-stage biotechnology company using its pioneering gene-editing platform to develop life-saving cell and gene therapies, today published an article in Frontiers Bioenginnering, demonstrating the efficacy of its TALEN® engineered FAP UCART-cells in cancer-associated fibroblast (CAF) depletion, reduction of desmoplasia and tumor infiltration.

Adoptive cell therapy based on chimeric antigen receptor-engineered T (CAR-T) cells has proven to be lifesaving for many cancer patients.

However, its therapeutic efficacy has so far been restricted to only a few malignancies, with solid tumors proving to be especially recalcitrant to efficient therapy. Poor intra-tumor infiltration by T cells and T cell dysfunction due to a desmoplastic, immunosuppressive microenvironment are key barriers for CAR T-cell success against solid tumors.-

Cancer-associated fibroblasts (CAFs) are critical components of the tumor stroma, evolving specifically within the tumor microenvironment (TME). The CAF secretome is a significant contributor to the extracellular matrix and a plethora of cytokines and growth factors that induce immune suppression. Together they form a physical and chemical barrier which induces a T cell-excluding ‘cold’ TME. CAF depletion in stroma rich solid tumors can thus provide an opportunity to convert immune evasive tumors susceptible to tumor-antigen CAR T-cell cytotoxicity.

Cellectis used its TALEN®-based gene editing platform to engineer non-alloreactive, immune-evasive UCAR T-cells targeting the unique CAF marker Fibroblast Activation Protein, alpha (FAP) to test whether FAP UCAR T-cell pre-treatment can make ‘cold’ tumors susceptible to subsequent tumor-antigen targeting CAR T-cells. Cellectis also generated non-alloreactive CAR T-cells against the tumor associated antigen (TAA) Mesothelin which is overexpressed in most solid tumors including mesothelioma and large sub-sets of ovarian, breast, pancreatic and lung adenocarcinomas. The combination treatment strategy was tested in a pre-clinical mouse model of triple-negative breast cancer (TNBC), an aggressive, stroma-rich breast cancer sub-type with poor prognosis and very limited treatment options at present.

Over 90% of epithelial cancers including breast, colorectal, pancreatic and lung adenocarcinomas express the CAF-specific surface marker, fibroblast activation protein α (FAP), which makes it a promising CAR T-cell target. In this study, we propose a novel and versatile approach of combination CAR T-cell therapy that can be extended to most stroma-rich cold tumors with relevant tumor-antigen targeting CAR T-cells which otherwise are recalcitrant to cell therapy”, said Shipra Das, Ph.D., Senior Scientist & Team Leader at Cellectis.


Preclinical data showed that :

  • In a mouse xenograft model, successful implantation of injected CAFs in the tumors was confirmed by positive staining of spindle-like cells with human-specific FAP antibody, recapitulating a physiologically relevant TNBC tumor with tumor and stromal compartments.
  • FAP UCART-cells alone significantly reduced tumor growth.
  • In vitro and in vivo results show that FAP UCART-cells enable the reprogramming of the cold, stroma-rich triple negative breast cancer (TNBC) TME, making the tumor susceptible to subsequent Meso UCAR T infiltration and cytotoxicity and improving the overall antitumor activity of the treatment.
  • In the context of combination therapy with anti-PD1 checkpoint inhibitor, maximal anti-tumor activity and survival benefits were observed upon FAP UCAR T-cell treatment followed by Meso UCAR T-cell treatment.

This article is available on Frontiers Bioengineering website by clicking on this link

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