Insight Into The Photo-controllable Structural Stability Of IRE1 Fluorescent Inhibitors For Bioactivation

Activation of the IRE1/XBP1 pathway is crucial in human diseases.Coumarin-based derivatives acting as IRE1 inhibitors and bright fluorophores are highly desirable to establish an integrated fluorescent inhibitor system.In the early stage,it was found that its electron withdrawing stimulation response unit could ortho stabilize and sequentially release fluorescent drugs.In this project,eight coumarin-based IRE1 prodrugs we had obtained,which was based on the ortho-stabilization of a photocaged IRE1 inhibitor PC-D-F07.Theoretical and experimental methods were applied to investigate the potential mechanism of the structural stability of PC-D-F07,the photoactivated fluorescence response and active IRE1 inhibitor release,and the repolarization of macrophages for antitumor immunotherapy.Here we took insight into the aqueous stability of PC-D-F07 through structure activity relationship（SAR）.The substituent effects indicated that the electron-withdrawing-NO₂moiety in the photocage combined with the tricyclic coumarin fluorophore contributing to the structural stability of PC-D-F07.To optimize the photocage of PC-D-F07,we incorporated1-ethyl-2-nitrobenzyl or 2-nitrobenzyl photolabile moiety on the hydroxyl group of IRE1inhibitor to generate RF-7 and RF-8.Upon photoactivation,both RF-7 and RF-8 presented an increased fluorescence response,sequentially enabling the unlock of the ortho-1,3-dioxane acetal for the release of active IRE1 inhibitors.Moreover,RF-7 exhibited a high repolarization ratio of converting M2-type tumor associated macrophages（M2-TAMs）to M1-type immune-responsive macrophages.This thesis provided a novel prodrug strategy which could be used for modulating druggable fluorophore backbones to achieve spatiotemporally controllable drug release for precise cancer treatment.