Preformulation Studies for the Development of a Parenteral Liquid Formulation of the Immunomodulator, Peldesine

Abstract

Peldesine (BCX-34) is a potent inhibitor of the enzyme purine nucleoside phosphorylase (PNP). The object of this study was to determine the preformulation parameters of BCX-34 and subsequently prepare a sterile liquid formulation for intravenous infusion. Ionization and solubility parameters were assessed prior to formulation development. Three pKa values of approximately 4.0, 5.2 and 10.3 were assigned for BCX-34. The pH-solubility profile showed an increase in solubility when the pH of the solution was less than the pKa₁ value of 4.0 and when the pH was more than the pKa₃ value of 10.3. BCX-34 has an octanol-water partition coefficient of approximately 7:1 (Log P = 0.8). The Van't Hoff temperature dependent solubility when measured over a range of 4 - 40°C produced a heat of solution (ΔH_c) of 7.68 kcal/mole. Based on these preformulation observations, two parenteral formulations containing 1 and 5 mg/mL of BCX-34 were prepared in an acidified saline solution and filled into 30cc and 100cc glass vials. Both formulation batches were sterile filtered, while only one 1 mg/mL batch was terminally autoclaved. The long-term stability of both solutions was performed and compared. Results of this study show that the drug product was stable. Following a screening study, Lactated Ringer's injection USP was selected as a suitable infusion medium for the dilution of the drug concentrate solutions.