Characterization and release mechanism of melittin entrapped poly (lactic acid-co-glycolic acid) microspheres

Goserelin/PLGA solid dispersion used to prepare long-acting microspheres with reduced initial release and reduced fluctuation of drug serum concentration in vivo

To prepare Goserelin (GOS) loaded long-acting microspheres with reduced initial release and prolonged drug release time of GOS, GOS/PLGA solid dispersion (by hot-melt extrusion, HME) was dissolved/dispersed in dichloromethane (DCM) to prepare microspheres by O/W method. From results of molecular dynamics simulation, PLGA and GOS molecules completely and uniformly dissolved and dispersed in DCM, respectively. In F5 microspheres (prepared by HME-O/W method), GOS existed as molecular or amorphous state, but not aggregation. Burst release of F5 microspheres (2.75%) was similar with Zoladex^TM implant (0.39%) and less than F10 microspheres (prepared by S/O/W method, 25.92%). After lag phase, GOS released rapidly from F5 microspheres and the cumulative release on the 45^th days was 95.14%. After injection of F5 microspheres, GOS serum concentration was relative steady at the range of 27.64-175.27 ng/mL for nearly 35 days. AUC_{(0-35 day)} of F5 microspheres was almost 2 times that of F10 microspheres. Pharmacodynamics study also showed potential effect of F5 microspheres on inhibiting the secretion of testosterone in male rats. HME-O/W method is potential to establish long-acting PLGA microspheres (loading water-soluble drug) , exhibiting stable drug serum concentration in vivo, and without large concentration fluctuation or serious pain/side effects.

Engineering Quick- and Long-acting Naloxone Delivery Systems for Treating Opioid Overdose

Purpose

Opioids have been the main factor for drug overdose deaths in the United States. Current naloxone delivery systems are effective in mitigating the opioid effects only for hours. Naloxone-loaded poly(lactide-co-glycolide) (PLGA) microparticles were prepared as quick- and long-acting naloxone delivery systems to extend the naloxone effect as an opioid antidote.

Methods

The naloxone-PLGA microparticles were made using an emulsification solvent extraction approach with different formulation and processing parameters. Two PLGA polymers with the lactide:glycolide (L:G) ratios of 50:50 and 75:25 were used, and the drug loading was varied from 21% to 51%. Two different microparticles of different sizes with the average diameters of 23 μm and 50 μm were produced using two homogenization-sieving conditions. All the microparticles were critically characterized, and three of them were evaluated with β-arrestin recruitment assays.

Results

The naloxone encapsulation efficiency (EE) was in the range of 70–85%. The EE was enhanced when the theoretical naloxone loading was increased from 30% to 60%, the L:G ratio was changed from 50:50 to 75:25, and the average size of the particles was reduced from 50 μm to 23 μm. The in vitro naloxone release duration ranged from 4 to 35 days. Reducing the average size of the microparticles from 50 μm to 23 μm helped eliminate the lag phase and obtain the steady-state drug release profile. The cellular pharmacodynamics of three selected formulations were evaluated by applying DAMGO, a synthetic opioid peptide agonist to a μ-opioid receptor, to recruit β-arrestin 2.

Conclusions

Naloxone released from the three selected formulations could inhibit DAMGO-induced β-arrestin 2 recruitment. This indicates that the proposed naloxone delivery system is adequate for opioid reversal during the naloxone release duration.

The effect of polymer blends on initial release regulation and in vitro-in vivo relationship of peptides loaded PLGA-Hydrogel Microspheres

The aim of this study was to resolve the lag time problem for peptides loaded PLGA-Hydrogel Microspheres (PLGA-gel-Ms) by blending low molecular PLGA (Mw. 1 kDa) into PLGA (Mw. 10 kDa) as an intrinsic porogen, and then assess the in vitro-in vivo relationship (IVIVR). Here, Goserelin acetate (GOS) was chosen as the model peptides. When compared to additional types of porogen, the intrinsic porogen avoided impurities remaining and protected the bioactivities of the peptides. By adding 10% PLGA (Mw. 1 kDa), the lag time was eliminated both in vitro and in vivo with a desirable EE (97.04% ± 0.51%). The release mechanisms were found to be: a) initial GOS release mainly controlled by pores diffusion and b) autocatalysis of PLGA (Mw. 1 kDa) which increased the quantity of aqueous pores, as revealed by SEM images. To solve the challenges caused by multiphasic release profiles, for the first time the Segmented phases IVIVR were proposed and developed, and showed improved linear fitting effects and supported the proposed release mechanisms. The application of PLGA blends could provide a new insight into PLGA microsphere initial release rate regulation.

Quality by design thinking in the development of long-acting injectable PLGA/PLA-based microspheres for peptide and protein drug delivery

Adopting the Quality by Design (QbD) approach in the drug development process has transformed from "nice-to-do" into a crucial and required part of the development, ensuring the quality of pharmaceutical products throughout their whole life cycles. This review is discussing the implementation of the QbD thinking into the production of long-acting injectable (LAI) PLGA/PLA-based microspheres for the therapeutic peptide and protein drug delivery. Various key elements of the QbD approaches are initially elaborated using Bydureon®, a commercial product of LAI PLGA/PLA-based microspheres, as a classical example. Subsequently, the factors influencing the release patterns and the stability of the peptide and protein drugs are discussed. This is followed by a summary of the state-of-the-art of manufacturing LAI PLGA/PLA-based microspheres and the related critical process parameters (CPPs). Finally, a landscape of generic product development of LAI PLGA/PLA-based microspheres is reviewed including some major challenges in the field.