Antitumor activity and pharmacokinetic properties of PF-00299804, a second-generation irreversible pan-erbB receptor tyrosine kinase inhibitor.

Signaling through the erbB receptor family of tyrosine kinases contributes to the proliferation, differentiation, migration, and survival of a variety of cell types. Abnormalities in members of this receptor family have been shown to play a role in oncogenesis, thus making them attractive targets for anticancer treatments. PF-00299804 is a second-generation irreversible pan-erbB receptor tyrosine kinase inhibitor currently in phase I clinical trials. PF-00299804 is believed to irreversibly inhibit erbB tyrosine kinase activity through binding at the ATP site and covalent modification of nucleophilic cysteine residues in the catalytic domains of erbB family members. Oral administration of PF-00299804 causes significant antitumor activity, including marked tumor regressions in a variety of human tumor xenograft models that express and/or overexpress erbB family members or contain the double mutation (L858R/T790M) in erbB1 (EGFR) associated with resistance to gefitinib and erlotinib. Furthermore, PF-00299804 shows exceptional distribution to human tumor xenografts and excellent pharmacokinetic properties across species.

Tyrosine kinase inhibitors. 19. 6-Alkynamides of 4-anilinoquinazolines and 4-anilinopyrido[3,4-d]pyrimidines as irreversible inhibitors of the erbB family of tyrosine kinase receptors.

Structure-activity relationships for inhibition of erbB1, erbB2, and erbB4 were determined for a series of alkynamide analogues of quinazoline- and pyrido[3,4-d]pyrimidine-based compounds. The compounds were prepared by coupling the appropriate 6-aminoquinazolines or 6-aminopyrido[3,4-d]pyrimidines with alkynoic acids, using EDCI.HCl in pyridine. The compounds showed pan-erbB enzyme inhibition but were on average about 10-fold more potent against erbB1 than against erbB2 and erbB4. For cellular inhibition, the nature of the alkylating side chains was an important determinant, with 5-dialkylamino-2-pentynamide type Michael acceptors providing the highest potency. This is suggested to be due to an improved ability of the amine to participate in an autocatalysis of the Michael reaction with enzyme cysteine residues. Pyrido[3,4-d]pyrimidine analogue 39 was selected for in vivo evaluation and achieved tumor regressions at 10 mg/kg in the A431 human epidermoid carcinoma and at 40 mg/kg for the SF767 human glioblastoma and the SKOV3 human ovarian carcinoma. Complete stasis was observed at 40 mg/kg in the BXPC3 human pancreatic carcinoma as well as in the H125 human non-small-cell lung carcinoma.

Tyrosine Kinase Inhibitors. 20. Optimization of Substituted Quinazoline and Pyrido[3,4-d]pyrimidine Derivatives as Orally Active, Irreversible Inhibitors of the Epidermal Growth Factor Receptor Family.

Structure-activity relationships for inhibition of erbB1, erbB2, and erbB4 were determined for a series of quinazoline- and pyrido[3,4-d]pyrimidine-based analogues of the irreversible pan-erbB inhibitor, canertinib. Cyclic amine bearing crotonamides were determined to provide rapid inhibition of cellular erbB1 autophosphorylation and good metabolic stability in liver microsome and hepatocyte assays. The influence of 4-anilino substitution on pan-erbB inhibitory potency was investigated. Several anilines were identified as providing potent, reversible pan-erbB inhibition. Optimum 4- and 6-substituents with known 7-substituents provided preferred irreversible inhibitors for pharmacodynamic testing in vivo. Quinazoline 54 and pyrido[3,4-d]pyrimidine 71 were identified as clearly superior to canertinib. Both compounds possess a piperidinyl crotonamide Michael acceptor and a 3-chloro-4-fluoroaniline, indicating these as optimized 6- and 4-substituents, respectively. Pharmacokinetic comparison of compounds 54 and 71 across three species selected compound 54 as the preferred candidate. Compound 54 (PF-00299804) has been assigned the nomenclature of dacomitinib and is currently under clinical evaluation.

DFTMP, an NMR reagent for assessing the near-neutral pH of biological samples.

A new NMR chemical shift standard and pH indicator, difluorotrimethylsilanylphosphonic acid (DFTMP), is described, and the utility of this reagent is demonstrated for in situ determination of pH in complex biofluids. The pH dependence of this reagent allows accurate in situ determination of aqueous solution pH to within an RMSE of 0.02 pH units over a pH range of 5 to 8. Advantages of this reagent over previously described pH-sensitive components include (1) lack of metal binding affinity, (2) minimal disturbance of endogenous spectral regions, and (3) the potential to function as a multinuclear pH indicator and chemical shift reference point for 19F, 1H, and 31P nuclei. This reagent will be generally useful for NMR experiments on biological systems where the pH needs to be accurately measured at the moment of data acquisition.