Abstract: The present invention has identified compounds with extended aromatic chromophores that bind the G-quadruplex formed by the folding of single-stranded human telomeric DNA. These compounds have been shown to be effective telomerase inhibitors and are contemplated to be useful in developing cancer treatments. A model of cationic porphyrin interaction with quadruplex DNA by intercalation has been established and in combination with structure activity relations has provided novel porphyrin compounds that exhibit discrimination between binding duplex and quadruplex DNA and show improved activity against telomerase.