Probing in Vitro Release Kinetics of Long-Acting Injectable Nanosuspensions via Flow-NMR Spectroscopy

Development of Flow-NMR Spectroscopy for Real-Time Monitoring and Kinetics Studies of Biomolecules: Case Study of Liraglutide Oligomerization

We report the development of a comprehensive flow-NMR methodology for mechanistic studies of biomolecules. This approach allows for systematic kinetic investigation via precise sample condition modulations. Traditionally utilized for reaction monitoring and kinetic studies of small molecules, the application of flow-NMR to larger biomolecules, such as peptide oligomers and proteins, has remained unexplored. Here, we present a pioneering study using flow-NMR to examine the pH-dependent oligomeric interconversion of liraglutide, a glucagon-like peptide 1 (GLP-1) receptor agonist known for its efficacy in managing type 2 diabetes and obesity. Liraglutide molecules are prone to forming distinct oligomers and even fibrils under certain conditions, influencing their stability, absorption, and bioavailability─factors critically important in pharmaceutical applications. The developed methodologies and suite of flow-NMR experiments collectively yield comprehensive insights into the interconversion process of liraglutide without resorting to combining multiple other techniques. It incorporates various 1D and pseudo-2D proton NMR experiments, including GUPPY-DOSY, a newly developed version of a flow-compatible DOSY experiment, to monitor critical parameters such as diffusion coefficients (D), transverse relaxation (R2), and structural similarity. The relative ease of setting up and executing this set of flow-NMR experiments offers a straightforward path to extending their application to the characterization of other complex systems, including therapeutic proteins and biologic drugs.

Deconstructing Annealing Phenomena in Modified Release Lipid Multiparticulates

This work investigates annealing-induced changes in modified release lipid multiparticulates composed of glyceryl behenate and poloxamer 407. Multiparticulates were manufactured using multiple lots of excipients and then annealed at 3 different temperatures across 45-50 °C (75% RH) until kinetically stable dissolution profiles were achieved. Throughout annealing, multiparticulates were analyzed using powder X-ray diffraction, scanning electron microscopy, quantitative 1H NMR, Raman spectroscopy, and novel flow-NMR dissolution techniques. Supporting nonlinear mixed effects models helped systematically link these orthogonal tools to dissolution, altogether providing strong evidence of concurrent glyceryl behenate crystal refinement with phase separation and migration of the poloxamer 407 from glyceryl behenate as the drivers for changes in dissolution with annealing. These findings demonstrate the importance of annealing glyceryl behenate-poloxamer 407 multiparticulates to achieve the complex matrix needed for modified release.

Drug Nanocrystals for Active Tumor-Targeted Drug Delivery

Drug nanocrystals, which are comprised of active pharmaceutical ingredients and only a small amount of essential stabilizers, have the ability to improve the solubility, dissolution and bioavailability of poorly water-soluble drugs; in turn, drug nanocrystal technology can be utilized to develop novel formulations of chemotherapeutic drugs. Compared with passive targeting strategy, active tumor-targeted drug delivery, typically enabled by specific targeting ligands or molecules modified onto the surface of nanomedicines, circumvents the weak and heterogeneous enhanced permeability and retention (EPR) effect in human tumors and overcomes the disadvantages of nonspecific drug distribution, high administration dosage and undesired side effects, thereby contributing to improving the efficacy and safety of conventional nanomedicines for chemotherapy. Continuous efforts have been made in the development of active tumor-targeted drug nanocrystals delivery systems in recent years, most of which are encouraging and also enlightening for further investigation and clinical translation.

Interpreting In Vitro Release Performance from Long-Acting Parenteral Nanosuspensions Using USP-4 Dissolution and Spectroscopic Techniques

Injectable sustained release dosage forms have emerged as desirable therapeutic routes for patients that require life-long treatments. The prevalence of drug molecules with low aqueous solubility and bioavailability has added momentum toward the development of suspension-based long-acting parenteral (LAP) formulations; the previously undesirable physicochemical properties of Biopharmaceutics Classification System (BCS) Class II/IV compounds are best suited for extended release applications. Effective in vitro release (IVR) testing of crystalline suspensions affirms product quality during early-stage development and provides connections with in vivo performance. However, before in vitro-in vivo correlations (IVIVCs) can be established, it is necessary to evaluate formulation attributes that directly affect IVR properties. In this work, a series of crystalline LAP nanosuspensions were formulated with different stabilizing polymers and applied to a continuous flow-through (USP-4) dissolution method. This technique confirmed the role of salt effects on the stability of polymer-coated nanoparticles through the detection of disparate active pharmaceutical ingredient (API) release profiles. The polymer stabilizers with extended hydrophilic chains exhibited elevated intrapolymer activity from the loss of hydrogen-bond cushioning in dissolution media with heightened ionic strength, confirmed through one-dimensional (1D) ¹H NMR and two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY) experiments. Thus, steric repulsion within the affected nanosuspensions was limited and release rates decreased. Additionally, the strength of interaction between hydrophobic polymer components and the API crystalline surface contributed to suspension dissolution properties, confirmed through solution- and solid-state spectroscopic analyses. This study provides a unique perspective on the dynamic interface between the crystalline drug and aqueous microenvironment during dissolution.