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Drug-regulated CD33-targeted CAR T cells control AML using clinically optimized rapamycin dosing
Jacob Appelbaum1,2,3,4, April E Price5, Kaori Oda1
1Seattle Children's Therapeutics, Seattle Children's Research Institute, Seattle, Washington, USA.
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.
Insights
Researchers developed DARIC33, a rapamycin-controlled therapy targeting CD33+ tumors. This controllable CAR T-cell therapy shows reversible control and potent anti-leukemic activity, paving the way for clinical applications.
Area of Science:
- Immunotherapy
- Cancer Biology
- Pharmacology
Background:
- Chimeric antigen receptor (CAR) T-cell therapy offers promise but lacks precise control over T-cell activity.
- Developing clinically translatable CAR designs with pharmacologic regulation is a critical need for enhancing safety and efficacy.
Purpose of the Study:
- To design and evaluate a novel, fully human, rapamycin-regulated CAR T-cell product, DARIC33, for targeting CD33+ malignancies.
- To demonstrate the reversible control of T-cell effector functions and in vivo antileukemic activity mediated by DARIC33 in response to rapamycin.
Main Methods:
- Development of the dimerizing agent-regulated immunoreceptor complex (DARIC33) targeting CD33.
- Assessment of target-specific and rapamycin-dependent cytokine release, cytotoxicity, and transcriptional responses in vitro.
- Evaluation of in vivo antileukemic activity in preclinical models and assessment of CD34+ stem cell function.
- Integration of pharmacokinetic data to establish a clinically applicable rapamycin dosing schedule.
Main Results:
- DARIC33 exhibited target-specific and rapamycin-dependent T-cell activation, cytokine release, and cytotoxicity at low rapamycin concentrations (1 nM).
- T-cell effector functions were reversibly controlled by rapamycin withdrawal and re-exposure.
- DARIC33 demonstrated potent in vivo antileukemic activity without impacting CD34+ stem cell function.
- A clinically applicable rapamycin dosing schedule was estimated, and a Phase I trial (PLAT-08) is underway with promising initial results.
Conclusions:
- The DARIC33 platform provides sensitive and reversible pharmacologic control over CAR T-cell activity.
- DARIC33 exhibits the potency and safety profile required for clinical translation in CD33+ malignancies.
- The DARIC platform holds potential for application to other immunotherapy targets requiring precise regulation.
