Metallacarboranes are versatile platforms commonly used to develop bioactive compounds with potential therapeutic applications. Their unusual cage-like structure enables us to arrange substituents and tailor molecular targets. Additionally, metallacarboranes can induce favorable interactions with biomolecules through hydrogen and dihydrogen bonding, ion-pairing, 8,9 hydrophobic interactions, and chaotropic effects. Among metallacarboranes, cobalt bis(dicarbollide) (COSAN) stands out for its properties. Amphiphilic COSAN self-assembles in aqueous solutions and interacts with lipid membranes and hydrophobic cavities of cyclodextrins or proteins. COSAN can also cross cell membranes and accumulate intracellularly, including in the cell nucleus. Furthermore, 3D aromaticity and a single negative charge delocalized over 23 atoms 26 explain the exceptional thermal, chemical, and biological stability of this abiotic compound. Combined, these properties have prompted advances in drug design and gene therapy, thus explaining the increasing popularity of COSAN in medicinal chemistry. As a pharmacophore, COSAN is commonly used to prepare biologically active hybrid organic-inorganic derivatives. These COSAN derivatives are applied as boron neutron capture therapy (BNCT) , radioimaging and magnetic resonance imaging probes, enzyme inhibitors , antimicrobial agents , and peptide modifiers They are also widely conjugated to nucleosides , antisense oligonucleotides , and DNA intercalators to improve their pharmacological properties. Given the increasing number and variety of COSAN applications in biosciences, the biological properties of COSAN derivatives must be judiciously characterized, particularly their interactions with biomacromolecules, including proteins, lipid membranes, and nucleic acids such as DNA.