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317 B7-H3-targeted CAR T cell with an inducible caspase 9 suicide gene effectively eradicates uveal melanoma liver metastases
  1. Marco Ventin1,
  2. Giulia Cattaneo2,
  3. Jingyu Jia3,
  4. Shahrzad Arya3,
  5. Luke Maggs3,
  6. Yi Sun4,
  7. Genevieve M Boland2,
  8. Russell W Jenkins5,6,
  9. Bruce R Ksander7,
  10. Rizwan Haq6,8,
  11. Xinhui Wang3,
  12. Sandra Ryeom9,
  13. Cristina R Ferrone10 and
  14. Soldano Ferrone3
  1. 1Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
  2. 2Massacusetts General Hospital, Boston, MA, USA
  3. 3Division of Surgical Oncology, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
  4. 4MGH, Brookline, MA, USA
  5. 5Massachusetts General Hospital Cancer Center, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
  6. 6Broad Institute of MIT and Harvard, Cambridge, MA, USA
  7. 7Department of Ophthalmology, Schepens Eye Research Institute of Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA
  8. 8Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
  9. 9Department of Surgery, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
  10. 10Cedars Sinai Medical Center, Department of Surgery, Los Angeles, CA, USA
  • Journal for ImmunoTherapy of Cancer (JITC) preprint. The copyright holder for this preprint are the authors/funders, who have granted JITC permission to display the preprint. All rights reserved. No reuse allowed without permission.


Background Most uveal melanoma (UM) patients will develop metastatic disease to the liver. No effective therapies are currently available to treat metastatic UM (mUM). B7-H3/CD276 is an immune checkpoint molecule expressed in many tumors and notably, expressed at high levels in mUM. Here we investigated the preclinical efficacy of a Chimeric Antigen Receptor (CAR) T cell-based immunotherapy targeting B7-H3. Our B7-H3-specific CAR construct includes an inducible caspase 9 (iC9) suicide gene controlled by the chemical induced of dimerization AP1903 in case of an adverse reaction. This mechanism allows rapid and conditional elimination of iC9.B7-H3 CAR T cells.

Methods B7-H3 expression on human UM tissue samples and cell lines was assessed by immunohistochemistry and flow cytometry. iC9.B7-H3 CAR T cells were generated from healthy donors’ peripheral blood mononuclear cells by transduction with a retroviral vector encoding a B7-H3-specifc CAR comprised of iC9 suicide gene and CD28 costimulatory domain. Antitumor activity of iC9.B7-H3 CAR T cells was tested in vitro with UM cell lines, mUM patient-derived organotypic tumor spheroids (PDOTS), and NSG mice.

Results High surface expression of B7-H3 was observed on human mUM tissue samples (n=6). Tested specimens demonstrated 50–100% (n=4) and 26–50% (n=2) of positively stained cells, with most (5/6) displaying moderate-strong intensity and only 1 demonstrating weak intensity of expression. Homogeneous B7-H3 expression was confirmed on primary and metastatic UM cell lines (n=6, 97 ± 6%). iC9.B7-H3 CAR T cells demonstrated specific and potent antitumor activity against UM cells at high and low E:T ratios (tumor killing: 90±5% at 1:1, 43±5% at 1:16), and complete eradication of B7-H3-expressing PDOTS. iC9.B7-H3 CAR T cells demonstrated robust expansion in vivo resulting in complete and sustainable eradication of UM liver metastases for over 120 days. Administration of AP1903 rapidly eliminated iC9.B7-H3 CAR T cells demonstrating the functionality of the iC9 safety-switch.

Conclusions Our study identified B7-H3 as a novel target for CAR T cell-based immunotherapy in mUM and demonstrates the preclinical efficacy of iC9.B7-H3 CAR T cells. Our findings strongly support the rationale for the design of a Phase I clinical trial to treat patients with mUM.

Ethics Approval Formalin-fixed paraffin-embedded tissue samples derived from surgically removed metastatic lesions of UM patients were collected under an Institutional Review Board (IRB) approved protocol and kindly provided by the Dr. G. Boland BioBank at Massachusetts General Hospital (MGH). Fresh mUM tumor samples from deidentified UM patients were obtained under Dana-Farber/Harvard Cancer Center IRB-approved protocols.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See

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