Development of Liposomal Formulations for 1,4-bis-L/L Methionine-Conjugated Mitoxantrone–Amino Acid Conjugates to Improve Pharmacokinetics and Therapeutic Efficacy

<b>Background:</b> 1,4-bis-L/L methionine-conjugated mitoxantrone-amino acid conjugate (L/LMet-MAC) inhibits topoisomerase IIα and enhances tumor cytotoxicity, but its short half-life limits therapeutic application. <b>Objective:</b> To improve the pharmacokinetics and antitumor efficacy of L/LMet-MAC through liposomal encapsulation. <b>Methods:</b> PEGylated DSPC liposomes containing EPG or prepared via the ammonium sulfate gradient method were employed to encapsulate L/LMet-MAC. Encapsulation efficiency, drug-to-lipid ratio, and serum stability were assessed. Pharmacokinetics, antitumor efficacy, and systemic safety were further evaluated in vivo. <b>Results:</b> L/LMet-MAC encapsulated in PEGylated DSPC liposomes containing EPG or prepared using the ammonium sulfate gradient method has high encapsulation efficiency. Further studies show that PEGylated DSPC liposomes prepared with the ammonium sulfate gradient approach display an efficient D/L ratio and serum stability as well as improved pharmacokinetics and enhanced antitumor efficacy while mitigating the side effects of L/LMet-MAC. <b>Conclusions:</b> PEGylated DSPC liposomes prepared using an ammonium sulfate gradient showed favorable performance for delivering L/LMet-MAC.