Rational Design of Putative Dual-Target Opioid-Dopaminergic Casomorphin-Ranatensin Hybrid Peptides: Computational Modeling and Preliminary Antiproliferative Evaluation.

Despite advances in oncology, cancer remains a leading cause of mortality worldwide, and both μ-opioid receptor (MOR) and dopamine D2 receptor (D2R) signaling have been implicated in the regulation of tumor proliferation, survival, and progression, positioning them as attractive targets for multifunctional anticancer strategies. In the present study, a series of novel casomorphin-ranatensin hybrid peptides were designed, synthesized, and evaluated as putative dual-target anticancer agents combining MOR and D2R pharmacophores. Among the evaluated analogues, KAZO_5.2 and KAZO_7.2 reduced viability of HCT116 colorectal cancer cells in a dose- and time-dependent manner, with a modest selectivity ratio compared to non-tumorigenic MCF 10A cells. Both compounds showed favorable docking scores toward MOR and D2R, while single 100 ns molecular dynamics trajectories showed that the peptides remained associated with their respective receptor models over the simulated timescale. Partial reversal of the viability-reducing effect by naloxone suggested involvement of opioid-sensitive pathways, while only low baseline MOR expression was detected in HCT116 cells under our experimental conditions, consistent with a possible contribution of additional receptor-mediated mechanisms to the observed activity. Neither compound induced pronounced apoptosis or cell cycle arrest, suggesting cytostatic rather than cytotoxic effects. Both peptides exhibited negligible hemolytic activity and high proteolytic stability in human plasma, with intact peptides remaining predominant after 24 h of incubation at 37 °C. These findings identify casomorphin-ranatensin hybrids as a promising scaffold for dual-target anticancer peptide development, warranting further structural optimization and mechanistic investigation.