2-SUBSTITUTED AMINOPYRIDO[2,3-D]PYRIMIDIN-7(8H) ONES - STRUCTURE-ACTIVITY-RELATIONSHIPS AGAINST SELECTED TYROSINE KINASES AND IN-VITRO AND IN-VIVO ANTICANCER ACTIVITY

While engaged in therapeutic intervention against a number of prolifer ative diseases, we have discovered the 2-aminopyrido[2,3-d]pyrimidin-7 (8H)-ones as a novel class of potent, broadly active tyrosine kinase ( TK) inhibitors. An efficient route was developed that enabled the synt hesis of a wide variety of analogues with substitution on several posi tions of the template. From the lead structure 2, a series of analogue s bearing variable substituents at the C-2 position and methyl or ethy l at N-8 was made. Compounds of this series were competitive with ATP and displayed submicromolar to low nanomolar potency against a panel o f TKs, including receptor (platelet-derived growth factor, PDGFr; fibr oblast growth factor, FGFr; epidermal growth factor, EGFr) and nonrece ptor (c-Src) classes. One of the more thoroughly evaluated members was 63 with IC50 values of 0.079 mu M (PDGFr), 0.043 mu M (bFGFr), 0.044 mu M (EGFr), and 0.009 mu M (c-Src). In cellular studies, 63 inhibited PDGF-mediated receptor autophosphorylation in a number of cell lines at IC50 values of 0.026-0.002 mu M and proliferation of two PDGF-depen dent lines at 0.3 mu M. It also caused inhibition of soft agar colony formation in three cell lines that overexpress the c-Src TK, with IC50 values of 0.33-1.8 mu M. In in vivo studies against a panel of seven xenograft tumor models with known and/or inferred dependence on the EG Fr, PDGFr, and c-Src TKs, compound 63 produced a tumor growth delay of 10.6 days against the relatively refractory SK-OV-3 ovarian xenograft and also displayed activity against the HT-29 tumor. In rat oral bioa vailability studies, compound 63 plasma concentrations declined in a b iexponential manner, and systemic plasma clearance was high relative t o liver blood flow. Finally, in rat metabolism studies, HPLC chromatog raphy identified two metabolites of 63, which were proved by mass spec trometry and synthesis to be the primary amine (58) and N-oxide (66). Because of the excellent potency of 63 against selected TKs, in vitro and in vivo studies are underway for this compound in additional tumor models dependent upon PDGFr, FGFr, and c-Src to assess its potential for advancement to clinical trials.