The interactions of PT-ACRAMTU, a cytotoxic platinum-acridine conjugate, with the human telomeric G-quadruplex have been studied using in-line high-performance liquid chromatography-mass spectrometry and footprinting assays. The conjugate reacts significantly faster with quadruplex DNA (t(1/2) = 1.2 h) than with double-stranded DNA, and A-N7, and not G-N7, is the kinetically preferred target, an unprecedented reactivity feature in platinum-DNA interactions. Unlike the clinical platinum drug cisplatin, which targets the human telomeric sequence nonspecifically, the platinum-intercalator technology has the potential to produce telomere-specific anticancer agents via a mechanism that kinetically discriminates between G and A in the two DNA secondary structures.