Design synthesis and biological evaluation of substituted pyrrolo23-dpyrimidines as multiple receptor tyrosine kinase inhibitors and antiangiogenic agents

摘要

Direct and indirect involvement of Receptor Tyrosine Kinases (RTKs) in tumor growth and metastasis makes them ideal targets for anticancer therapy. A paradigm shift from inhibition of single RTK to inhibition of multiple RTKs has been recently demonstrated. We designed and synthesized eight N⁴-phenylsubstituted-6-(2-phenylethylsubstituted)- 7H-pyrrolo[2,3-d]pyrimidine-2,4-diamines as homologated series of our previously published RTK inhibitors. We reasoned that increased flexibility of the side chain, that determines potency and selectivity, would improve the spectrum of RTK inhibition. These compounds were synthesized using a bis-electrophilic cyclization to afford substituted pyrrolo[2,3-d]pyrimidines followed by chlorination and substitution at the 4- position with various anilines. Five additional compounds of this series were previously reported by Gangjee et al. with activities against IGFR only. There synthesis, characterization and biological activities against a variety of other RTKs are reported in this study for the first time. The biological evaluation, in whole cell assays, showed several analogs had remarkable inhibitory activity against epithelial growth factor receptor (EGFR), vascular endothelial growth factor receptor-1 (VEGFR-1), platelet derived growth factor receptor-β (PDGFR-β), the growth of A431 cells in culture and in the chicken embryo chorioallantoic membrane (CAM) angiogenesis assay. The inhibitory data against the RTKs in this study demonstrates that variation of the 6-ethylaryl substituents as well as the N⁴-phenyl substituents of these analogs does indeed control both the potency and specificity of inhibitory activity against RTKs. In addition, homologation of the chain length of the 6-substituent from a methylene to an ethyl increases the spectrum of RTK inhibition. New multi-RTK inhibitors (>8, >12) and potent inhibitors of angiogenesis (>15, >19) were identified with the best compound, N⁴-(3- trifluromethylphenyl)-6-(2-phenylethyl)-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamine (>15), with an IC50 value of 30 nM in the CAM angiogenesis inhibition assay.