Downstream processing of spray-dried ASD with hypromellose acetate succinate - Roller compaction and subsequent compression into high ASD load tablets

Ten years of the manufacturing classification system: a review of literature applications and an extension of the framework to continuous manufacture

The MCS initiative was first introduced in 2013. Since then, two MCS papers have been published: the first proposing a structured approach to consider the impact of drug substance physical properties on manufacturability and the second outlining real world examples of MCS principles. By 2023, both publications had been extensively cited by over 240 publications. This article firstly reviews this citing work and considers how the MCS concepts have been received and are being applied. Secondly, we will extend the MCS framework to continuous manufacture. The review structure follows the flow of drug product development focussing first on optimisation of API properties. The exploitation of links between API particle properties and manufacturability using large datasets seems particularly promising. Subsequently, applications of the MCS for formulation design include a detailed look at the impact of percolation threshold, the role of excipients and how other classification systems can be of assistance. The final review section focusses on manufacturing process development, covering the impact of strain rate sensitivity and modelling applications. The second part of the paper focuses on continuous processing proposing a parallel MCS framework alongside the existing batch manufacturing guidance. Specifically, we propose that continuous direct compression can accommodate a wider range of API properties compared to its batch equivalent.

Emerging Applications of Hydroxypropyl Methylcellulose Acetate Succinate: Different Aspects in Drug Delivery and Its Commercial Potential

Hydroxypropyl methylcellulose acetate succinate (HPMCAS) has multi-disciplinary applications spanning across the development of drug delivery systems, in 3D printing, and in tissue engineering, etc. HPMCAS helps in maintaining the drug in a super-saturated condition by inhibiting its precipitation, thereby increasing the rate and extent of dissolution in the aqueous media. HPMCAS has several distinctive characteristics, such as being amphiphilic in nature, having an ionization pH, and a succinyl and acetyl substitution ratio, all of which are beneficial while developing formulations. This review provides insights regarding the various types of formulations being developed using HPMCAS, including amorphous solid dispersion (ASD), amorphous nanoparticles, dry coating, and 3D printing, along with their applicability in drug delivery and biomedical fields. Furthermore, HPMCAS, compared with other carbohydrate polymers, shows several benefits in drug delivery, including proficiency in imparting stable ASD with a high dissolution rate, being easily processable, and enhancing bioavailability. The various commercially available formulations, regulatory considerations, and key patents containing the HPMCAS have been discussed in this review.

Impact of Gastric pH Variations on the Release of Amorphous Solid Dispersion Formulations Containing a Weakly Basic Drug and Enteric Polymers

Enteric polymers are widely used in amorphous solid dispersion (ASD) formulations. The aim of the current study was to explore ASD failure mechanisms across a wide range of pH conditions that mimic in vivo gastric compartment variations where enteric polymers such as hydroxypropyl methylcellulose phthalate (HPMCP) and hydroxypropyl methylcellulose acetate succinate (HPMCAS) are largely insoluble. Delamanid (DLM), a weakly basic drug used to treat tuberculosis, was selected as the model compound. Both DLM free base and the edisylate salt were formulated with HPMCP, while DLM edisylate ASDs were also prepared with different grades of HPMCAS. Two-stage release testing was conducted with the gastric stage pH varied between pH 1.6 and 5.0, prior to transfer to intestinal conditions of pH 6.5. ASD particles were collected following suspension in the gastric compartment and evaluated using X-ray powder diffraction and scanning electron microscopy. Additional samples were also evaluated with polarized light microscopy. In general, ASDs with HPMCP showed improved overall release for all testing conditions, relative to ASDs with HPMCAS. ASDs with the edisylate salt likewise outperformed those with DLM free base. Impaired release for certain formulations at intestinal pH conditions was attributed to surface drug crystallization that initiated during suspension in the gastric compartment where the polymer is insoluble; crystallization appeared more extensive for HPMCAS ASDs. These findings suggest that gastric pH variations should be evaluated for ASD formulations containing weakly basic drugs and enteric polymers.

Downstream Processing of Itraconazole:HPMCAS Amorphous Solid Dispersion: From Hot-Melt Extrudate to Tablet Using a Quality by Design Approach

The downstream processing of hot-melt extruded amorphous solid dispersions (ASDs) into tablets is challenging due to the low tabletability of milled ASDs. Typically, the extrudate strand is sized before milling, as the strand cannot be fed directly into the milling system. At the lab scale, the strand can be sized by hand-cutting before milling. For scaling up, pelletizers or chill roll and flaker systems can be used to break strands. Due to the different techniques used, differences in milling and tablet compaction are to be expected. We present a systematic study of the milling and tableting of an extruded ASD of itraconazole with hypromellose acetate succinate (HPMCAS) as a carrier polymer. The strand was sized using different techniques at the end of the extruder barrel (hand-cutting, pelletizer, or chill roll and flaker) before being milled at varying milling speeds with varying screen sizes. The effects of these variables (sizing technology, milling speed, and screen size) on the critical quality attributes (CQAs) of the milled ASD, such as yield, mean particle size (D50), tablet compaction characteristics, and tablet dissolution, were established using response surface methodology. It was found that the CQAs varied according to sizing technology, with chill roll flakes showing the highest percentage yield, the lowest D50, and the highest tabletability and dissolution rate for itraconazole. Pearson correlation coefficient tests indicated D50 as the most important CQA related to tabletability and dissolution. For certain milling conditions, the milling of hand-cut filaments results in similar particle size distributions (PSDs) to the milling of pellets or chill roll flakes.