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Probing the Interplay between Amorphous Solid Dispersion Stability and Polymer Functionality.

ABSTRACT: Amorphous solid dispersions containing a polymeric component often impart improved stability against crystallization for a small molecule relative to the pure amorphous form. However, the relationship between side chain functionalities on a polymer and the ability of a polymer to stabilize against crystallization is not well understood. To shed light on this relationship, a series of polymers were functionalized from a parent batch of poly(chloromethylstyrene- co-styrene) to investigate the effect of functionality on the stability in amorphous solid dispersions without altering the physical parameters of polymers, such as the average molecular weight or backbone chain chemistry. The kinetics of the crystallization of the nonsteroidal anti-inflammatory drug nabumetone from amorphous solid dispersions containing each functionalized polymer were interpreted on the basis of two interactions: hydrogen bonding between the drug and the polymer and the solubility of the polymer in the amorphous drug. It was found that hydrogen bonding between functionalized polymers and nabumetone can impart stability against crystallization, but only if the polymer shows significant solubility in amorphous nabumetone. Methylation of a protic functionality can improve the ability of a polymer to inhibit nabumetone crystallization by increasing the solubility in the drug, even when the resulting polymer lacks hydrogen bonding functionalities to interact with the pharmaceutical. Furthermore, factors, such as the glass transition temperature of pure polymers, were uncorrelated with isothermal nucleation rates. These findings inform a framework relating polymer functionality and stability deconvoluted from the polymer chain length or backbone chemistry with the potential to aid in the design of polymers to inhibit the crystallization of hydrophobic drugs from amorphous solid dispersions.

SUBMITTER: Frank DS

PROVIDER: S-EPMC6296464 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Probing the Interplay between Amorphous Solid Dispersion Stability and Polymer Functionality.

Frank Derek S DS Matzger Adam J AJ

Molecular pharmaceutics 20180620 7

Amorphous solid dispersions containing a polymeric component often impart improved stability against crystallization for a small molecule relative to the pure amorphous form. However, the relationship between side chain functionalities on a polymer and the ability of a polymer to stabilize against crystallization is not well understood. To shed light on this relationship, a series of polymers were functionalized from a parent batch of poly(chloromethylstyrene- co-styrene) to investigate the effe ...[more]

PMID: 29924614

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Project description:Niclosamide is an FDA-approved anthelmintic that is being studied in clinical trials as a chemotherapeutic and broad-spectrum antiviral. Additionally, several other applications are currently in the preclinical stage. Unfortunately, niclosamide is a poorly water soluble molecule, with reduced oral bioavailability, which hinders its use for new indications. Moreover, niclosamide is a poor glass former; in other words, the molecule has a high tendency to recrystallize, and it is virtually impossible to generate a stable amorphous solid employing the neat molecule. Previously, our group reported the development of an amorphous solid dispersion (ASD) of niclosamide (niclosamide ASD) that generates nanoparticles during its dissolution, not only increasing niclosamide's apparent solubility from 6.6 ± 0.4 to 481.7 ± 22.2 µg/mL in fasted state simulated intestinal fluid (FaSSIF) but also its oral bioavailability 2.6-fold in Sprague-Dawley rats after being administered as a suspension. Nevertheless, niclosamide ASD undergoes recrystallization in acidic media, and an enteric oral dosage form is needed for its translation into the clinic. In this work, we further characterized the nanoparticles that generated during the dissolution of the niclosamide ASD. Cryogenic transmission electron microscopy (Cryo-TEM) and wide-angle X-ray scattering (WAXS) revealed that the nanoparticles were amorphous and had a particle size of ~150 nm. The oral dosage forms of niclosamide ASD were formulated using commercial enteric capsules (Capsuline® and EudracapTM) and as enteric-coated tablets. The enteric dosage forms were tested using pH-shift dissolution and acid-uptake tests, using the USP type II dissolution apparatus and the disintegration apparatus, respectively. The capsules exhibited a higher percentage of weight gain, and visual rupture of the Capsuline capsules was observed. Eudracap capsules protected the formulation from the acidic media, but polymer gelling and the formation of a nondispersible plug were noted during dissolution testing. In contrast, enteric-coated tablets protected the formulation from acid ingress and maintained the performance of niclosamide ASD granules during dissolution in FaSSIF media. These enteric-coated tablets were administered to beagle dogs at a niclosamide dose of 75 mg/kg, resulting in plasma concentrations of niclosamide higher than those reported in the literature using solubilized niclosamide at a higher dose (i.e., 100 mg/kg). In summary, an enteric oral dosage form of niclosamide ASD was formulated without hindering the generation of nanoparticles while maintaining the increase in the niclosamide's apparent solubility. The enteric-coated tablets successfully increased the niclosamide plasma levels in dogs when compared to a niclosamide solution prepared using organic solvents.

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Probing the Interplay between Amorphous Solid Dispersion Stability and Polymer Functionality.

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Probing the Interplay between Amorphous Solid Dispersion Stability and Polymer Functionality.

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