• Terry J Fry, Nirali N Shah, Rimas J Orentas, Maryalice Stetler-Stevenson, Constance M Yuan, Sneha Ramakrishna, Pamela Wolters, Staci Martin, Cindy Delbrook, Bonnie Yates, Haneen Shalabi, Thomas J Fountaine, Jack F Shern, Robbie G Majzner, David F Stroncek, Marianna Sabatino, Yang Feng, Dimiter S Dimitrov, Ling Zhang, Sang Nguyen, Haiying Qin, Boro Dropulic, Daniel W Lee, and Crystal L Mackall.
• Pediatric Oncology Branch, Center for Cancer Research, National Institutes of Health (NIH), Bethesda, Maryland, USA.
• Nat. Med. 2018 Jan 1; 24 (1): 20-28.

AbstractChimeric antigen receptor (CAR) T cells targeting CD19 mediate potent effects in relapsed and/or refractory pre-B cell acute lymphoblastic leukemia (B-ALL), but antigen loss is a frequent cause of resistance to CD19-targeted immunotherapy. CD22 is also expressed in most cases of B-ALL and is usually retained following CD19 loss. We report results from a phase 1 trial testing a new CD22-targeted CAR (CD22-CAR) in 21 children and adults, including 17 who were previously treated with CD19-directed immunotherapy. Dose-dependent antileukemic activity was observed, with complete remission obtained in 73% (11/15) of patients receiving ≥1 × 106 CD22-CAR T cells per kg body weight, including 5 of 5 patients with CD19dim or CD19- B-ALL. Median remission duration was 6 months. Relapses were associated with diminished CD22 site density that likely permitted CD22+ cell escape from killing by CD22-CAR T cells. These results are the first to establish the clinical activity of a CD22-CAR in B-ALL, including leukemia resistant to anti-CD19 immunotherapy, demonstrating potency against B-ALL comparable to that of CD19-CAR at biologically active doses. Our results also highlight the critical role played by antigen density in regulating CAR function.

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