VP, Clinical Pharmacology, DMPK and Pharmacometrics Aera Therapeutics, United States
Disclosure(s):
Husain Attarwala: No relevant disclosure to display
Background: In vivo engineering of CAR T cells using lipid nanoparticles (LNPs) [1] represents a transformative therapeutic modality, offering scalable, non-viral delivery of mRNA to immune cells. We have developed a CD8+ T-cell-targeted LNP (tLNP) encapsulating mRNA encoding a CD20-directed chimeric antigen receptor (CAR) as a surrogate system to demonstrate pharmacologic effect in non-human primates (NHPs). In NHPs, systemic tLNP administration resulted in transient CAR expression on endogenous CD8+ T cells and subsequent depletion of CD20+ B cells in both peripheral blood and spleen. To characterize the in vivo dynamics and inform translational dosing strategies, we developed a pharmacokinetic/cellular kinetic/pharmacodynamic (PK/CK/PD) model [2,3].
Methods: NHPs were administered multiple doses of tLNPs. The modeling framework integrated: Plasma mRNA pharmacokinetics (PK), CAR expression kinetics (CK) in circulating T cells, and Pharmacodynamic (PD) impact on CD20+ B-cell depletion. CAR expression was modeled as a function of mRNA exposure, with downstream PD effects driven by CAR T-cell-mediated B-cell cytotoxicity in blood and spleen. CAR T-cell clearance incorporated both first-order elimination and a target-mediated CAR-T clearance (TMCC) pathway reflective of CAR/B-cell interaction.
Results: The model robustly recapitulated observed in vivo data. mRNA PK profiles, consistent across single and repeat dosing, were well captured. CAR expression was transient and scaled linearly with mRNA exposure. Importantly, CAR T-cell clearance dynamics were dose- and exposure-dependent. Initial doses exhibited rapid clearance via TMCC due to high B-cell burden. Subsequent doses, administered post-partial B-cell depletion, exhibited reduced TMCC and prolonged CAR T-cell persistence. This dynamic translated into more durable and extensive B-cell depletion upon repeat dosing.
Conclusions: Developed semi-mechanistic model elucidates the exposure-response relationship of in vivo engineered CAR T cells following LNP-mediated mRNA delivery. The framework enables simulation of dosing regimens and supports optimization of LNP dose levels for maximal B-cell depletion. These insights guide preclinical development and lay the groundwork for rational clinical translation of the mRNA-LNP in vivo CAR-T platform—a novel, modular approach to programmable immunotherapy.
Citations: [1] Hartmann, Jessica, et al. "Clinical development of CAR T cells—challenges and opportunities in translating innovative treatment concepts." EMBO molecular medicine 9.9 (2017): 1183-1197. [2] Attarwala, Husain, et al. "Translational pharmacokinetic/pharmacodynamic model for mRNA-3927, an investigational therapeutic for the treatment of propionic acidemia." nucleic acid therapeutics 33.2 (2023): 141-147. [3] Singh, Aman P., et al. "Development of a quantitative relationship between CAR-affinity, antigen abundance, tumor cell depletion and CAR-T cell expansion using a multiscale systems PK-PD model." MAbs. Vol. 12. No. 1. Taylor & Francis, 2020.
