In the absence of any evidence of COSAN binding to dsDNA, we assessed COSAN effects on ssDNA hybridization. COSAN should more easily form complexes with ssDNA than with dsDNA because 1) ssDNA has a lower surface charge density than dsDNA, weakening the repulsive Coulombic forces between COSAN and DNA, 2) ssDNA is more flexible than dsDNA, facilitating the conformational adaptation of DNA to COSAN, and 3) ssDNA has exposed nucleobases, providing additional potential partners for COSAN binding. Our CD measurements of oligoDNA before and after its thermal melting showed that COSAN does not interfere with the annealing of two complementary DNA single strands. Therefore, COSAN does not significantly interact with ssDNA, in line with previous studies on metallacarborane-modified oligonucleotides, which formed complexes with complementary nucleic acid strands. Our findings indicate that COSAN and, most likely, other metallacarboranes are poor pharmacophores for nucleic acid-binding drugs. Instead, COSAN should be used to target nucleic acid-binding proteins -such as transcription factors, histones, topoisomerases, polymerases, or DNA methyltransferaseswhich are components of biomolecular condensates and participate in many vital cellular processes. Because the dysfunction of these proteins has been implicated in many diseases, including cancer, small molecules capable of modulating their activity have a high therapeutic potential.