Cytotoxic agent combretastatin A4

Combretastatin A-4 (CA-4), a potentially potent anticancer agent with poor aqueous solubility and chemical instability, poses significant challenges for clinical translation. In this study, we report the encapsulation of CA-4 in sub-10 nm unimer micelles (UMs) derived from amphiphilic random copolymers of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and perfluoroalkyl acrylate (FA), synthesized via ARGET-ATRP. These copolymers self-fold in aqueous media to form compact single-chain nanoparticles that efficiently encapsulate CA-4, achieving encapsulation efficiencies up to 95 % at 19:1 copolymer/drug weight ratio. The resulting nanocarriers significantly enhanced the solubility and stability of CA-4 in phosphate-buffered saline over two months, while preserving its cis-configuration and biological activity. Drug release profiles demonstrated controlled diffusion and appeared to be influenced by copolymer composition, i.e. the hydrophilic/hydrophobic balance. Fluorescently labeled UMs were readily internalized by cancer cells within minutes, supporting their potential as ultrasmall, responsive drug nanocarriers. In vitro cytotoxicity studies demonstrated that encapsulated CA-4 maintained similar potency compared to the free drug against MIA PaCa-2 (IC₅₀ = 4.9 ± 0.6 nM vs. 3.3 ± 1.4 nM) and A2780 (IC₅₀ = 2.7 ± 0.6 nM vs. 2.0 ± 0.5 nM) cancer cell lines, while showing enhanced activity in A375 melanoma cells (IC₅₀ = 4.8 ± 0.7 nM vs. 8.1 ± 1.3 nM).

Herein, we designed, synthesized, and studied the activity of a novel dual-action red light-activatable Pt-(IV) prodrug BDP-Pt-CA4 with a BODIPY fluorophore and CA4 in axial positions, capable of light-controlled release of two chemotherapeutic drugs: cisplatin and combretastatin A4 (CA4). To the best of our knowledge, this is the first example of a dual-action photoactive Pt-(IV)-CA4 prodrug that releases two antiproliferative agents upon red light irradiation. The aim of this work was to demonstrate light-induced release of CA4 and cisplatin from the prodrug, occurring strictly on demand to reduce the overall toxicity of the drug and minimize the damaging effect on normal tissues. In addition to in vitro evidence of light-induced release of two chemotherapeutic agents, a controllable release of both drugs inside cancer cells was also proven. For the first time, a light-induced release of the tubulin polymerization inhibitor from a photoactivatable prodrug was observed via quantification of subtle changes in the mechanistic properties of cell surfaces via single-cell low-stress scanning ion conductance microscopy (SICM). Our results clearly demonstrate a perspective for photoactive Pt-(IV) prodrugs, confirming an ability to release the platinum agent "on demand", and to act as light-controlled dual-action chemotherapy.