Transitioning from a lab-scale PLGA microparticle formulation to pilot-scale manufacturing

The complexity of scale-up manufacturing of PLGA microparticles creates a significant challenge when transitioning from benchtop-scale formulation development into larger clinical scale batches. Minor changes in the initial formulation composition (e.g., PLGA molecular weight, solvent type, and drug concentration) and processing parameters (e.g., extraction kinetics and drying condition) during scale-up production can result in significantly different performance of the prepared microparticles. The objectives of the present study were to highlight the in vitro and in vivo performance of a candidate benchtop-scale batch created with a rotor-stator mixer, transitioned into an in-line manufacturing process at ~15× scale of a long-acting naltrexone formulation. Physicochemical properties (such as drug loading, residual benzyl alcohol content, and morphology) as well as the in vitro release characteristics of the prepared naltrexone microparticles between the benchtop-scale and in-line process pilot-scale were determined. The pharmacokinetics of the naltrexone microspheres were investigated using the rat model. The results demonstrate that while the morphologies of the particles were different from a visual assessment and slight differences were observed in the in vitro release profiles, the in vivo pharmacokinetics illustrate similar kinetics. Our study shows that scale-up production having the same drug release kinetics can be made by controlling the formulation and processing parameters.