Positional Isomerization of A Non‐Cleavable Combi‐Molecule Dramatically Altered Tumor Cell Response Profile

Abstract

To potentiate the quinazoline-based inhibitor of the epidermal growth factor receptor (EGFR), a chloroethyl alkylating moiety was appended to its 6-position. This led to molecules with extremely strong EGFR inhibitory potency and anomalously strong DNA-damaging potential. To assess the role of the chloroethyl group on potency, we designed a molecule in which it is shifted to the 7-position where it would be less reactive and away from the cys773 of the EGFR ATP site. The results showed that (i) ZR2009 was 10-fold less potent than its positional isomer ZR2003 in EGFR tyrosine kinase inhibition, (ii) it consistently exhibited significantly weaker antiproliferative potency than ZR2003, (iii) in reversibility assays, while ZR2003 induced sustained inhibition of EGFR phosphorylation, ZR2009 inhibitory activity was partially reversed, and (iv) likewise, ZR2009 significantly lost its activity in short exposure growth inhibitory assays and induced lower levels of DNA damage than ZR2003. Molecular modeling suggested that while the chloroethylamino group in ZR2003 was at 3.5 Å away from Cys773, that of ZR2009 was at 6.3 Å. The results in toto suggest that, while the chloroethyl is a strong alkylating group, its appendage to the 6-position is optimal for DNA damage, sustained EGFR, and growth inhibition.

Quantitative Analysis of the Potency of Equimolar Two-Drug Combinations and Combi-Molecules Involving Kinase Inhibitors In Vitro: The Concept of Balanced Targeting

“…Type I combi-molecules are designed to block only one target as an intact molecule and require hydrolysis to be able to block their secondary target [8,[20][21][22]. Type II combi-molecules are dual-targeting molecules that do not require hydrolysis to hit their two targets [23,24]. The targeting mode that is referred to as type II is the most commonly used approach in the literature and the resulting molecules are often referred to as hybrid or chimeric molecules [25,26].…”

15N-, 13C- and 1H-NMR Spectroscopy Characterization and Growth Inhibitory Potency of a Combi-Molecule Synthesized by Acetylation of an Unstable Monoalkyltriazene

“…This approach seeks to design molecules termed “combi-molecules” to behave as bioactive species on their own and to further be hydrolyzed into other bioactive species. Agents that require hydrolysis to generate bioactive species are termed type I combi-molecules [ 12 ] and those that do not require hydrolysis to exert multiple activities, type II [ 13 ]. Recently, such a type of molecule 6-(3-methyltriaz-1-en-1-yl)-1 H -benzo[de]isoquinoline-1,3(2 H )-dione, EG22 ( 8a , Scheme 2 ), was designed to behave as an inhibitor of a DNA repair protein termed “poly(adenosine diphosphate ribose) polymerase” (PARP) and a DNA alkylating agent.…”