Synthesis and evaluation of 1-substituted imidazo[4,5-c] quinoline TLR7 agonists with improved potency
Author ORCID Identifier
Date of Award
Chemistry (BA, BS)
Dr. L. Nathan Tumey
Science and Mathematics
Antibody-drug conjugates ; Tumors -- Treatment ; Toll-like receptor 7
TLR7 agonists are small molecules that are useful within cancer immunotherapy due to their ability to stimulate the TLR7 pathway resulting in NFκB activation, and cytokine release.1 Due to the risk of toxicity when delivered systemically, our team has employed a particular type of drug-delivery technology, Antibody Drug Conjugates (ADCs) to deliver these payloads directly to tumor tissue. The initial focus of this work was on E104 (8a), an imidazoquinoline TLR7 agonist, which was synthesized by the Tumey lab.1 However, the agonist was not sufficiently potent for many of the proposed applications of this technology, prompting a need to develop more potent derivatives of this compound. Initial derivatives were synthesized through amine couplings at the benzylic substituent and were characterized using HPLC and NMR. The derivatives were further evaluated using Ramos Blue Cell activation assays as well as PAMPA permeability assays, resulting in the identification of compounds 9b, 11b and 12b as potent payloads with sufficient
permeability for ADC applications. Generally, hydrophobic appendages attached to the benzyl group significantly enhanced the potency of the payloads and multiple analogs were found to be ~10x more potent than the parent E104 molecule. Although these specific payloads proved to be sufficiently potent, they proved to have limited reactivity and our initial studies showed them to be incompatible with typical ADC linkers. Linker payload synthesis difficulties were overcome by attempting to create new payloads using the reductive amination method in which a secondary amine was a part of the functional group alteration. This allowed for linker attachment with the more reactive amine as compared to the amine attached onto the quinoline which is more poorly nucleophilic. These new generation payloads were also characterized by HPLC, UPLC and NMR and additionally evaluated for their ability to stimulate the TLR7 pathway and induce NFκB activation. Although they proved not to have improved potency to E104, compound 13a proved to have modest potency and this new type of payload proved compatibility with the cleavable mcValCitPABC linker, paving the way for future efforts surrounding optimization of these payloads.
DeYoung, Emma Grace, "Synthesis and evaluation of 1-substituted imidazo[4,5-c] quinoline TLR7 agonists with improved potency" (2023). Undergraduate Honors Theses. 25.