IMAGING IMMUNITY – from Nanoscale to Macroscale | Insights from Biophysics
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Invited Lecture | Patrick Schlegel, Tübingen

Session chair: Gemma Dias (Oxford, UK)
Date: Tuesday, 14 January, 2020, 4:15 PM - 5:00 PM


4:15 PM -01

Adapter CAR T-cells (AdCAR-T) allow precise control on effector function, prevent antigen evasion and enable differential target cell lysis, based on complex antigen expression profiles (#37)

Christian Seitz1, Jörg Mittelstaet2, Ann-Christin Krahl1, Philipp Knopf3, Jana Hau1, Selina Reiter1, Sarah Schroeder1, Giulia Bender1, Clara Illi1, Verena Kieble1, Sabine Schleicher1, Stefan Grote1, Karin Schilbach1, Manfred Kneiling3, Bernd Pichler3, 4, Dominik Lock2, Andrew Kaiser2, Peter Lang1, 4, Rupert Handgretinger1, 4, Patrick Schlegel1, 4

1 University Children's Hospital Tuebingen, Tuebingen, Baden-Württemberg, Germany
2 Miltenyi Biotec, Bergisch Gladbach, North Rhine-Westphalia, Germany
3 Preclinical Imaging and Radiopharmacy, Tuebingen, Baden-Württemberg, Germany
4 iFIT Cluster of Excellence (EXE 2180), Tuebingen, Baden-Württemberg, Germany


Despite tremendous clinical success targeting B-phenotypic malignancies, translation of chimeric antigen receptor (CAR)-T therapy to a broader spectrum of indications is limited in terms of safety and efficacy. Conventional CARs can only transmit an on- (presence of antigen) or off-signal (absence of antigen). Life-threatening acute (cytokine release syndrome and neurotoxicity) and chronic (on-target off-tumor activity) toxicities are the consequence. While, B-cell function can be substituted, elimination of vitally essential tissues might not be compatible with life, restraining the availability of target antigens. Moreover, conventional CAR design limits the efficacy of CAR-T. Continuous stimulation causes CAR-T exhaustion. Antigen evasion, as a result of monovalent selection pressure, arises as the leading cause of therapy failure.

To address these limitations, we have engineered the adapter-CAR (AdCAR) system. AdCAR technology is based on a split recognition/activation design in which effector cells are redirected to surface expressed antigens via biotinylated adapter molecules (AMs). Importantly, the AdCAR is exclusively targeted to biotin in the context of a specific linker structure, referred to as Linker-Label-Epitope (LLE). No competition with physiological biotin was found. LLEs can be easily conjugated to novel or preexisting AM formats like monoclonal antibodies (mAbs) or mAb fragments in a GMP-compliant manner. Expressed on T cells, the AdCAR was found to mediate effector function equally potent as conventional CARs in vitro and in vivo against a multiplicity of target antigens, exclusively in the presence of antigen-specific LLE-conjugated AMs. AdCAR technology was demonstrated to allow precise temporal (on/off), quantitative (adjust intensity) as well as qualitative (change and combine target antigens) control on CAR-T activity and function. Moreover, AdCAR-T allow simultaneous and sequential targeting of multiple antigens (“OR”-gate), preventing resistance to therapy by antigen evasion as demonstrated for single and double antigen loss. Unprecedented, AdCAR-T are capable to identify and differentially lyse target cells by integration of AM mediated signals based on multiplex antigen expression profiles (“AND”-gate). We were able to demonstrate that application of combinations of AMs, targeting multiple antigens expressed on the same cell, at concentrations below an individual threshold, combine in a highly synergistic manner to mediate AdCAR-T activation by assembling LLE-signals on the surface of the target cell. This effect, referred to as surface activation matrix (SAM), was shown to allow selective elimination of target cells with partly shared expression profile in co-culture experiments.

In conclusion, AdCAR technology provides advanced controllability on CAR-T function, flexibility in target antigen selection and selectivity to differentiate between cancerous and heathy tissues, addressing all outlined limitations.



Keywords: CAR t-cells, antigen expression, AdCAR-T