Project Grant R21CA299243

IMAGE-GUIDED ADAPTABLE CAR T CELL THERAPY FOR SOLID TUMORS - PROJECT SUMMARY DESPITE PROMISING RESULTS IN TREATING B CELL MALIGNANCIES, OVER 50% OF PATIENTS UNDERGOING CHIMERIC ANTIGEN RECEPTOR (CAR) T CELL THERAPY EXPERIENCE TUMOR RELAPSE, AND CAR T CELLS HAVE NOT CONSISTENTLY SHOWN EFFECTIVENESS AGAINST SOLID TUMORS. ANTIGEN ESCAPE, T CELL EXHAUSTION, AND SEVERE TOXICITIES REMAIN MAJOR OBSTACLES. THIS PROPOSAL ADDRESSES THESE CHALLENGES BY DEVELOPING AN IMAGE-GUIDED, UNIVERSAL, ADAPTABLE CAR (A-CAR) SYSTEM COMPRISING A TUMOR-TARGETING ADAPTOR MOLECULE FUSED WITH A C-TERMINAL TAG AND A TAG-SPECIFIC CAR ON T CELLS. OUR STEPWISE APPROACH TO IMAGE-GUIDED CAR T CELL THERAPY INVOLVES: (1) IMAGING: PET ASSESSMENT OF ADAPTOR BIODISTRIBUTION USING RADIOLABELED VHH ADAPTORS; (2) TREATMENT: A SINGLE INFUSION OF AUTOLOGOUS TAG-SPECIFIC CAR T CELLS WITH OPTIMIZED VHH ADAPTORS THAT COAT TUMOR CELLS FOR CAR T RECOGNITION; AND (3) ASSESSMENT: MONITORING TUMOR RESPONSE AND CAR T DISTRIBUTION VIA 18F-FDG AND 68GA-DOTATATE PET/CT. THE CLINICALLY APPROVED RADIOTRACER 68GA-DOTATATE TRACKS CAR T CELL EXPANSION AND ACTIVITY AT ON- AND OFF-TUMOR SITES THROUGH BINDING TO SOMATOSTATIN RECEPTOR 2 (SSTR2) CO-EXPRESSED ON CAR T CELLS. THE HIGH SPECIFICITY, AFFINITY, AND FAVORABLE KINETICS OF VHHS MAKE THEM IDEAL FOR PET IMAGING AND AS CAR T CELL ADAPTORS, ENABLING NON-INVASIVE DETECTION OF ANTIGEN EXPRESSION, PATIENT SELECTION, AND PREDICTION OF HOMING SITES AND OFFTUMOR TOXICITY PRIOR TO TREATMENT. THIS PROJECT COMPREHENSIVELY INVESTIGATES VHHS AS CAR T ADAPTORS, INCLUDING PHARMACOKINETIC AND BIODISTRIBUTION CHARACTERIZATION, OPTIMIZATION OF DELIVERY (INTERMITTENT CYCLIC TUMOR TAGGING VS. CONTINUOUS INFUSION) AND DOSING, AND THE POTENTIAL TO MITIGATE T CELL EXHAUSTION AND OVERCOME ANTIGEN ESCAPE THROUGH MULTI-ANTIGEN TARGETING. MOUSE XENOGRAFT AND SYNGENEIC TUMOR MODELS ARE ESSENTIAL FOR THIS WORK, AS THEY ARE THE ONLY SYSTEMS IN WHICH VHH ADAPTOR BIODISTRIBUTION, CAR T CELL TRAFFICKING, TUMOR TARGETING, AND TOXICITY CAN BE EVALUATED TOGETHER IN A LIVING ORGANISM. THESE IN VIVO MODELS ENABLE OPTIMIZATION OF ADAPTOR AND CAR T DOSING, ASSESSMENT OF ANTIGEN ESCAPE AND EXHAUSTION UNDER PHYSIOLOGICAL CONDITIONS, AND VALIDATION OF PET IMAGING AS A PREDICTIVE TOOL - NONE OF WHICH ARE ACHIEVABLE IN CELL CULTURE. BY REFINING VHH AND CAR T DELIVERY GUIDED BY QUANTITATIVE IMAGING, WE SEEK TO ENHANCE EFFICACY AND MINIMIZE OFF-TUMOR TOXICITY, WITH THE ULTIMATE GOAL OF ADVANCING A-CAR THERAPY AGAINST SOLID CANCERS.