New long-acting injectable microspheres prepared by IVL-DrugFluidic™ system: 1-month and 3-month in vivo drug delivery of leuprolide.

The microspheres for 1-month (PLGA-based) and 3-month (PLA-based) drug releases of leuprolide were manufactured using an IVL-DrugFluidic™ system and their morphology, particle size and distribution, and encapsulation efficiency were compared with the commercialized products. In vivo test was also conducted to monitor the amount of leuprolide and testosterone in plasma after a single subcutaneous injection in male Sprague-Dawley (SD) rats and male Beagle dogs. The median diameter, span value, drug loading, and encapsulation efficiency of PLGA-based microspheres (63.29 μm, 0.26, 13.15%, and 78.90%, respectively) and PLA-based microspheres (80.28 μm, 0.21, 14.42%, and 86.50%, respectively) demonstrated narrow particle size distribution (monodispersed) and efficient drug loading/encapsulation efficiency. Both the microspheres exhibited a desired time-dependent drug release profile and reduced initial burst release by 16-fold in SD rats and 240-fold in Beagle dogs compared to Leuplin DPS®. Moreover, the testosterone level in plasma was suppressed to < 0.50 ng/mL after 28 days with a steady plasma drug concentration. The results suggested that newly developed leuprolide-loaded microspheres produced by the IVL-DrugFluidic™ system could provide extended drug release with advantages such as reduced initial burst release and testosterone level suppression, along with steady plasma drug concentration, over the existing products.