Novel N⁹-Substituted 6-Cycloalkylaminoadenines as Promising Compounds Against Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) accounts for 15% of breast cancers, exhibiting high proliferation and resistance to conventional treatments, highlighting the need for innovative therapies. Purine derivatives are recognised for their anticancer potential, making them valuable candidates for drug development. In the present study, we sought to uncover the anticancer potential of novel 6-cycloalkylaminoadenine compounds and elucidate their mechanism of action. A versatile synthetic pathway was developed to prepare two series of new 6-cycloalkylaminoadenines that combine the adenine scaffold with morpholino and N-methylpiperazine units. The method starts with the preparation of imidazole-based amidrazone precursors, which were obtained from 5-amino-4-cyanoformimidoylimidazoles and 4-aminomorpholine or 4-methylaminopiperazine. The reaction of these amidrazone precursors with triethyl orthoformate under reflux gave the target 6-cycloalkylaminoadenines. The compounds' cytotoxicity on the TNBC cell line MDA-MB-231 was assessed, with the best IC₅₀ values around 60-70 μM. The most promising compound, 3.2a, inhibits the migratory and invasive capacities of TNBC cells and promotes actin cytoskeleton reorganisation. Additionally, this compound induces caspase-3 activation, which promotes DNA fragmentation and ultimately leads to cell death. Molecular docking studies with key proteins involved in major signalling pathways associated with cancer progression further revealed that compound 3.2a has a higher affinity for CDK1. Altogether, our findings provide preliminary evidence supporting the potential of 6-cycloalkylaminoadenines in TNBC treatment.