Etoposide Phosphate

Etoposide phosphate is a water-soluble prodrug of etoposide that is rapidly converted to the active moiety etoposide following intravenous administration. Etoposide exerts its anticancer effects by targeting topoisomerase II, an enzyme essential for managing DNA topology during replication and transcription. Etoposide disrupts this process by stabilizing the transient cleavage complex between topoisomerase II and DNA, preventing the re-ligation step and resulting in the accumulation of double-strand breaks. Accumulated DSBs trigger cellular responses such as cell cycle arrest, apoptosis, and mitotic catastrophe. Etoposide exerts cytotoxic effects most effectively during the S and G2 phases of the cell cycle, when DNA replication and repair processes are actively engaged.
Beyond apoptosis, etoposide can initiate other forms of cell death including necrosis, necroptosis, ferroptosis, pyroptosis, and parthanatos. Etoposide can also trigger immunogenic cell death, enhancing anti-tumor immunity by releasing damage-associated molecular patterns. The phosphate prodrug form improves the aqueous solubility of etoposide, allowing intravenous administration without the need for solubilizing excipients that can increase infusion-related toxicity.

Fig. 1 Etoposide exerts its mechanism of action by targeting and disrupting the function of topoisomerase Ⅱ. (Jang J Y.; et al. 2025)

Etoposide phosphate was encapsulated together with indium in lipid-stabilized nanoparticles via a reverse microemulsion system for cancer therapy and SPECT imaging. The nanoparticles exhibited dose-dependent cytotoxicity and induced apoptosis in H460 lung cancer cells through G2/M cell cycle arrest. In a mouse xenograft lung cancer model, the indium-etoposide phosphate nanoparticles significantly enhanced tumor growth inhibition compared to free etoposide phosphate. The nanoparticle system also enabled SPECT imaging through incorporation of 111In.

Fig. 2 Characterizations of Etoposide Phosphate nanoparticles. (Srinivas R.; et al. 2015)