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Drug-regulated CD33-targeted CAR T cells control AML using clinically optimized rapamycin dosing
Jacob Appelbaum, … , Alexander Astrakhan, Michael C. Jensen
Jacob Appelbaum, … , Alexander Astrakhan, Michael C. Jensen
Published March 19, 2024
Citation Information: J Clin Invest. 2024;134(9):e162593. https://doi.org/10.1172/JCI162593.
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Research Article Hematology

Drug-regulated CD33-targeted CAR T cells control AML using clinically optimized rapamycin dosing

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Abstract

Chimeric antigen receptor (CAR) designs that incorporate pharmacologic control are desirable; however, designs suitable for clinical translation are needed. We designed a fully human, rapamycin-regulated drug product for targeting CD33+ tumors called dimerizaing agent–regulated immunoreceptor complex (DARIC33). T cell products demonstrated target-specific and rapamycin-dependent cytokine release, transcriptional responses, cytotoxicity, and in vivo antileukemic activity in the presence of as little as 1 nM rapamycin. Rapamycin withdrawal paused DARIC33-stimulated T cell effector functions, which were restored following reexposure to rapamycin, demonstrating reversible effector function control. While rapamycin-regulated DARIC33 T cells were highly sensitive to target antigen, CD34+ stem cell colony-forming capacity was not impacted. We benchmarked DARIC33 potency relative to CD19 CAR T cells to estimate a T cell dose for clinical testing. In addition, we integrated in vitro and preclinical in vivo drug concentration thresholds for off-on state transitions, as well as murine and human rapamycin pharmacokinetics, to estimate a clinically applicable rapamycin dosing schedule. A phase I DARIC33 trial has been initiated (PLAT-08, NCT05105152), with initial evidence of rapamycin-regulated T cell activation and antitumor impact. Our findings provide evidence that the DARIC platform exhibits sensitive regulation and potency needed for clinical application to other important immunotherapy targets.

Authors

Jacob Appelbaum, April E. Price, Kaori Oda, Joy Zhang, Wai-Hang Leung, Giacomo Tampella, Dong Xia, Pauline P.L. So, Sarah K. Hilton, Claudya Evandy, Semanti Sarkar, Unja Martin, Anne-Rachel Krostag, Marissa Leonardi, Daniel E. Zak, Rachael Logan, Paula Lewis, Secil Franke-Welch, Njabulo Ngwenyama, Michael Fitzgerald, Niklas Tulberg, Stephanie Rawlings-Rhea, Rebecca A. Gardner, Kyle Jones, Angelica Sanabria, William Crago, John Timmer, Andrew Hollands, Brendan Eckelman, Sanela Bilic, Jim Woodworth, Adam Lamble, Philip D. Gregory, Jordan Jarjour, Mark Pogson, Joshua A. Gustafson, Alexander Astrakhan, Michael C. Jensen

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Figure 9

Clinical activity of rapamycin-activated SC-DARIC33 in patients.

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Clinical activity of rapamycin-activated SC-DARIC33 in patients.
(A) Exp...
(A) Expression of FRB by SC-DARIC33 is correlated with rapamycin exposure. SC-DARIC33 manufactured from a healthy donor was cultured overnight in medium alone or media supplemented with 1 nM rapamycin. The proportion of VHH+ and FRB+ cells is shown in the bar graph. Note the rightward shift of VHH+ cells following rapamycin exposure. (B) Progressive inflammatory changes and hemorrhagic conversion of a chloroma following administration of SC-DARIC33 to subject S002. Samples from chloroma tissues are shown in C and D. Photographs used with permission. (C) Rapamycin-activated FRB+ DARIC33 T cells are expanded within chloroma tissue. Paired blood and chloroma tissue from patient S002 were evaluated by flow cytometry. T cells expressing CD3 were analyzed for VHH and FRB expression. The proportion of VHH+ and FRB+ cells among CD3+ cells is shown in the bar graph. (D) Rapamycin-activated DARIC33 cells within chloroma tissue obtained from patient S002 express increased markers of activation including PD-1 and TIM3. The proportion of either VHH+FRB+ cells (green bars) or VHH– cells (gray bars) expressing PD-1 or TIM3 is shown. ***P < 0.001, χ2 test with Bonferroni correction for multiple tests. (E) Peripheral blood from patient S004 shows concurrent expansion of DARIC33 cells and reduction of CD33hi cells. (F) Quantification of antigen abundance, as measured by MFI, and expansion of SC-DARIC33 cells within blood samples. Peak SC-DARIC33 expansion is followed by decreased CD33 antigen expression. (G) Expression of activation/exhaustion markers by rapamycin-activated SC-DARIC33 cells, as assessed by flow cytometry. Boolean gating results are shown as pie graphs with overlapping arcs indicating multi-antigen expression. At later time points (days 17 and 21), expression of activation markers is increased among VHH+FRB+ cells.

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ISSN: 0021-9738 (print), 1558-8238 (online)

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