CIRI seminar: Dr. Brian WEBSTER

“ Self-driving armored CAR-T cells overcome a suppressive milieu and eradicate CD19+ Raji lymphoma in preclinical models “

Abstract: Chimeric  antigen  receptor  (CAR)  T  cells  typically  use  a  strong  constitutive  promoter  to  ensure maximal  long-term  CAR  expression.  However,  recent  evidence  suggests  that  restricting  the  timing and magnitude of CAR expression is functionally beneficial, whereas constitutive CAR activation may lead  to  exhaustion  and  loss  of  function.  We  created  a  self-driving  CD19-targeting  CAR,  which regulates  its  own  function  based  on the  presence  of  a  CD19  antigen  engaged  by  the  CAR  itself,  by  placing  self-driving  CAR19  constructs  under  transcriptional  control  of  synthetic  activator  protein  1 (AP1)-nuclear factor  κB  (NF -κB)  or  signal  transducer  and  activator  of  transcription  (STAT)5 promoters. CD19 antigen-regulated expression was observed for self-driving AP1-NFκB-CAR19, with CAR19  upregulation  within  18  h  after  exposure  to  target  CD19,  and  corresponded  to  the  level  of tumor burden. Self-driving  CAR-T  cells  showed  enhanced  tumor-dependent  activation,  expansion, and low exhaustion in vitro as compared to constitutively expressed EF1α and murine stem cell virus (MSCV)  CARs  and  mediated  tumor  regression  and  survival in Raji-bearing  NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ  (NSG)  mice.  Long-term  CAR  function  correlated  with  upregulated  CAR expression  within  24  h  of  exposure  to  tumor  antigen.  The  self-driving  AP1-NFκB-CAR19  circuit  was  also used to inducibly express dominant-negative  transforming  growth  factor  β  receptor  II(TGFBRIIdn), which effectively countered the negative effects of TGF-β on CAR-T activation. Thus, a self-driving  CAR  approach  may  offer  a  new  modality  to  express  CAR  and  auxiliary  proteins  by  enhancing CAR-T functional activity and limiting exhaustion