Cyclic naphthalene diimide 1 bound to hybrid-type tetraplex DNA from 5′-AGGG(TTAGGG)3-3′ (K = 8.6 × 106 M−1) with 260-fold greater affinity than that when binding to double stranded oligonucleotide consisting of 5′-GGG AGG TTT CGC-3′ and 3′-CCC TCC AAA GCG-5′ (nK = 3.3 × 104 M−1) with 0.5 μM of IC50 for telomerase activity.