Pentamidine-induced alteration in restriction endonuclease cleavage of plasmid DNA

Strategies to Obtain Encapsulation and Controlled Release of Pentamidine in Mesoporous Silica Nanoparticles

Pentamidine (PTM), an antiprotozoal agent used in clinics as pentamidine isethionate salt (PTM-S), recently showed high potential also for the treatment of cancer and myotonic dystrophy type I. However, a severe limit to the systemic administration of PTM is represented by its nephrotoxicity, leading to the need for a system able to achieve a controlled release of the drug. In this study, mesoporous silica nanoparticles (MSNs) were employed for the first time to encapsulate PTM. PTM-S was first used for loading experiments into bare (MSN-OH) and aminopropyl, cyanopropyl and carboxypropyl-functionalized MSNs (MSN-NH₂, MSN-CN and MSN-COOH respectively) but it was not adequately loaded in any MSNs. The free base of PTM (PTM-B) was then obtained from PTM-S and successfully loaded into MSNs. Specifically, MSN-COOH exhibited the highest loading capacity. In vitro evaluation of PTM-B kinetic release from the different MSNs was carried out. An influence of the functional groups in slowing the release of the drug, when compared to bare MSNs was observed. Altogether, these results demonstrate that MSN-COOH could be a promising system to achieve a controlled release of PTM.

Development of a liposome formulation for improved biodistribution and tumor accumulation of pentamidine for oncology applications

Pentamidine isethionate, widely used for the treatment of parasitic infections, has shown strong anticancer activity in cancer cells and models of melanoma and lung cancer. Systemic administration of pentamidine is associated with serious toxicities, particularly renal, affecting as many as 95% of patients (O'Brien et al., 1997). This work presents the development of a liposome pentamidine formulation for greater tumor accumulation and lower drug exposure to vulnerable tissues. Liposomes formulated with saturated/unsaturated phospholipids of different chain lengths, varying cholesterol content, and surface PEG were explored to understand the effects of such variations on drug release, encapsulation efficiency, stability and in vivo performance. Saturated phospholipids with longer chain lengths, higher cholesterol content and PEG resulted in greater stability. The optimal formulation obtained showed significantly lower clearance rate (3.6 ± 1.2 mL/h/Kg) and higher AUC0-inf (348 ± 31 μmol/L × h) in vivo when compared to free drug (414 ± 138 mL/h/Kg and 2.58 ± 0.74 μmol/L × h, respectively). In tumor-bearing mice, liposomal delivery decreased kidney drug levels by up to 5-fold at 6 and 24h post-administration. Tumor drug exposure was up to 12.7-fold greater with liposomal administration compared to free drug. Overall, the liposomal pentamidine formulation developed has significant potential for the treatment of solid tumors.