The Combi-Targeting Concept:  Synthesis of Stable Nitrosoureas Designed to Inhibit the Epidermal Growth Factor Receptor (EGFR)

Abstract

According to the "combi-targeting" concept, the EGFR tyrosine kinase (TK) inhibitory potency of compounds termed "combi-molecules" is critical for selective growth inhibition of tumor cells with disordered expression of EGFR or its closest family member erbB2. Here we report on the optimization of the EGFR TK inhibitory potency of the combi-molecules of the nitrosourea class by comparison with their aminoquinazoline and ureidoquinazoline precursors. This led to the discovery of a new structural parameter that influences their EGFR TK inhibitory potency, i.e., the torsion angle between the plane of the quinazoline ring and the ureido or the nitrosoureido moiety of the synthesized drugs. Compounds (3'-Cl and Br series) with small angles (0.5-3 degrees ) were generally stronger EGFR TK inhibitors than those with large angles (18-21 degrees ). This was further corroborated by ligand-receptor van der Waals interaction calculations that showed significant binding hindrance imposed by large torsion angles in the narrow ATP cleft of EGFR. Selective antiproliferative studies in a pair of mouse fibroblast NIH3T3 cells, one of which NIH3T3/neu being transfected with the erbB2 oncogene, showed that IC(50) values for inhibition of EGFR TK could be good predictors of their selective potency against the serum-stimulated growth of the erbB2-tranfected cell line (Pearson r = 0.8). On the basis of stability (t(1/2)), EGFR TK inhibitory potency (IC(50)), and selective erbB2 targeting, compound 23, a stable nitrosourea, was considered to have the structural requirements for further development.

Subcellular Distribution of a Fluorescence-Labeled Combi-Molecule Designed to Block Epidermal Growth Factor Receptor Tyrosine Kinase and Damage DNA with a Green Fluorescent Species

“…The growth of refractory tumors is driven by multiple signaling disorders that often cannot be blocked by the use of a single drug. The combi-molecule approach is the first that seeks to create molecules capable of blocking at least two divergent targets in the cells by allowing the intact molecules to block one target on their own and to degrade into other species directed at the same or different targets (18,20,22,23,26,40,41). To gain insight into the subcellular distribution and degradation of combimolecules, we designed a new prototype termed AL237 to (a) be fluorescent on its own and (b) degrade under physiologic conditions to FD105 (an EGFR inhibitor) that fluoresces in the blue and a DNA alkylating fragment that fluoresces in the green (see Fig.…”

“…These molecules, despite their combination-based design, were not developed with the purpose of eventually replacing the traditional chemotherapy but rather complementing it. Albeit, we showed that many prototypes (e.g., SMA41, FD137) showed stronger antiproliferative activity than classic combinations of drugs with the same mechanism of action (20,(23)(24)(25)(26).…”

Design and Synthesis of Novel Quinazoline Derivatives and Their Evaluation as PI3Ks Inhibitors

“…After filtration, the product obtained was washed with diethyl ether (3×10 mL) and was re-crystallized from methanol to give the pure corresponding compounds 10b. Yield 6-Nitroquinazolin-4-(3H)-one (11) 16) To 2 g of 2-amino-5-nitrobenzonitrile 1, 25 mL of formic acid were added and the mixture was refluxed for 6 h while stirring. The reaction mixture was then poured on ice water resulting in the formation of a yellow precipitate which was separated by filtration to give compound 11.…”

Synthesis and antiproliferative activities against Hep-G2 of salicylanide derivatives: potent inhibitors of the epidermal growth factor receptor (EGFR) tyrosine kinase

“…Molecules designed to block EGFR TK, a class of potent, selective, ATP-competitive inhibitors of EGFR TK, induced signaling on their own and further degrade to a DNA damaging species, should induce significant cell-killing in tumours [9,10]. The first molecular probe designed to verify the combitargeting postulates, was shown to strongly block the EGFR TK activity on its own in a short exposure enzyme assay [11,12].…”