4-(3-Bromoanilino)-6,7-dimethoxyquinazoline (32, PD 153035) is a very potent inhibitor (IC50 0.025 nM) of the tyrosine kinase activity of the epidermal growth factor receptor (EGFR), binding competitively at the ATP site. Structure-activity relationships for close analogues of 32 are very steep. Some derivatives have IC50s up to 80-fold better than predicted from simple additive binding energy arguments, yet analogues possessing combinations of similar phenyl and quinazoline substituents do not show this "supra-additive" effect. Because some substituents which are mildly deactivating by themselves can be strongly activating when used in the correct combinations, it is proposed that certain substituted analogues possess the ability to induce a change in the conformation of the receptor when they bind. There is some bulk tolerance for substitution in the 6- and 7-positions of the quinazoline, so that 32 is not the optimal inhibitor for the induced conformation. The diethoxy derivative 56 [4-(3-bromoanilino)-6,7-diethoxyquinazoline] shows an IC50 of 0.006 nM, making it the most potent inhibitor of the tyrosine kinase activity of the EGFR yet reported.

4-Anilinoquinazoline- and 4-anilinopyrido[3,2-d]pyrimidine-6-acrylamides substituted with solubilizing 7-alkylamine or 7-alkoxyamine side chains were prepared by reaction of the corresponding 6-amines with acrylic acid or acrylic acid anhydrides. In the pyrido[3,2-d]pyrimidine series, the intermediate 6-amino-7-alkylamines were prepared from 7-bromo-6-fluoropyrido[3,2-d]pyrimidine via Stille coupling with the appropriate stannane under palladium(0) catalysis. This proved a versatile method for the introduction of cationic solubilizing side chains. The compounds were evaluated for their inhibition of phosphorylation of the isolated EGFR enzyme and for inhibition of EGF-stimulated autophosphorylation of EGFR in A431 cells and of heregulin-stimulated autophosphorylation of erbB2 in MDA-MB 453 cells. Quinazoline analogues with 7-alkoxyamine solubilizing groups were potent irreversible inhibitors of the isolated EGFR enzyme, with IC(50[app]) values from 2 to 4 nM, and potently inhibited both EGFR and erbB2 autophosphorylation in cells. 7-Alkylamino- and 7-alkoxyaminopyrido[3,2-d]pyrimidines were also irreversible inhibitors with equal or superior potency against the isolated enzyme but were less effective in the cellular autophosphorylation assays. Both quinazoline- and pyrido[3,2-d]pyrimidine-6-acrylamides bound at the ATP site alkylating cysteine 773, as shown by electrospray ionization mass spectrometry, and had similar rates of absorptive and secretory transport in Caco-2 cells. A comparison of two 7-propoxymorpholide analogues showed that the pyrido[3,2-d]pyrimidine-6-acrylamide had greater amide instability and higher acrylamide reactivity, being converted to glutathione adducts in cells more rapidly than the corresponding quinazoline. This difference may contribute to the observed lower cellular potency of the pyrido[3,2-d]pyrimidine-6-acrylamides. Selected compounds showed high in vivo activity against A431 xenografts on oral dosing, with the quinazolines being superior to the pyrido[3,2-d]pyrimidines. Overall, the quinazolines proved superior to previous analogues in terms of aqueous solubility, potency, and in vivo antitumor activity, and one example (CI 1033) has been selected for clinical evaluation.

LY showed improvement in fasting and postprandial glycaemic parameters when administered once weekly in subjects with type 2 diabetes. The pharmacokinetics and safety profiles also support further investigation of this novel agent.

Following the discovery of 4-[(3-bromophenyl)amino]-6,7-dimethoxyquinazoline (4; PD 153035) as an extremely potent (IC(50) 0.025 nM) inhibitor of the tyrosine kinase activity of the epidermal growth factor receptor (EGFR), several fused tricyclic quinazoline analogues have been prepared and evaluated for their ability to inhibit the enzyme. The most potent compound was the linear imidazo[4,5-g]quinazoline (8), which exhibited an IC(50) of 0.008 nM for inhibition of phosphorylation of a fragment of phospholipase C-gamma-1 as substrate. While N-methyl analogues of 8 showed similar potency, analogous N-[2-(dimethylamino)ethyl] derivatives were less effective. The next most potent compounds were the linear pyrazoloquinazolines (19 and 20) (IC(50)s 0.34 and 0.44 nM) and pyrroloquinazoline (21) (IC(50) 0.44nM), while several other linear tricyclic ring systems of similar geometry to 8 (triazolo-, thiazolo-, and pyrazinoquinazolines) were less effective. In the imidazo[4,5-g]quinazoline and pyrroloquinazoline series, the corresponding angular isomers were also much less effective than the linear ones. These results are consistent with structure-activity relationship studies previously developed for the 4-[(3-bromophenyl)amino] quinazolines, which suggested that small electron-donating substituents at the 6- and 7-positions were desirable for high potency. Cellular studies of the linear imidazoloquinazoline 8 show that it can enter cells and rapidly and very selectively shut down EGF-stimulated signal transmission by binding competitively at the ATP site of the EGFR.