Dissolution Testing in Drug Product Development: Workshop Summary Report

Discriminative Dissolution Method Development Through an aQbD Approach

Using a one-factor-at-a-time approach for dissolution method and discrimination analysis can be time-consuming and may not yield the optimal and discriminative method. To address this, we have developed a two-stage workflow for the dissolution method development followed by demonstration of discrimination power through an analytical Quality by Design (aQbD) approach. In the first stage, an optimal dissolution method was achieved by determining the method operable design region (MODR) through a design of experiment study of the high-risk method-related parameters. In the second stage, we established a Formulation-Discrimination Correlation Diagram strategy to examine the method discrimination capability, through which one can determine the method discriminative design region (MDDR) and visualize the impact of each formulation parameter and their interactions on dissolution. The application of aQbD principles into a workflow provides a scientific-driven guidance for robust method development and demonstrating discrimination power for dissolution methods.

In-silico, in-vitro and ex-vivo evidence of combining silymarin phytopharmaceutical with piperine, and fulvic acid for enhancing its solubility and permeability

Non-alcoholic fatty liver disease is one of the leading causes of death worldwide. Even if with such a high mortality there is no definite treatment approved. Thus, there is a need to develop a formulation which can have multiple pharmacological activities. Herbal drugs are among the most promising compounds that act by different pharmacological actions. For increasing the bio-activity of Silymarin we had isolated five active biomarker molecules from silymarin extract (as a Phytopharmaceutical) in our previous work. It possesses lower bioavailability due to poor solubility, lesser permeability and first pass metabolism effect. Therefore, from the literature we had screened two bioavailability enhancers i.e. piperine and fulvic acid for overcoming the drawbacks associated with silymarin. Hence, in this study we had first explored the ADME-T parameters and then evaluated their in-silico activity for different enzymes involved in inflammation and fibrosis. Interestingly, it was found that besides the bioavailability enhancing property, piperine and fulvic acid also shown anti-inflammatory and anti-fibrotic action, particularly more activity was demonstrated by fulvic acid than piperine. Furthermore, the concentration of the bioavailability enhancers i.e. 20% FA and 10% PIP were optimized by QbD assisted solubility studies. Moreover, the percentage release and apparent permeability coefficient of the optimized formulation was found to be 95% and 90%, respectively as compared to 6.54*106 and 1.63*106 respectively by SM suspension alone. Furthermore, it was found that plain rhodamine solution penetrated only up to 10 um whereas, formulation penetrated up to 30 um. Thus, combining these three, can not only increase the bioavailability of silymarin, but might also, increase the physiological action synergistically.

Dissolution Profile Similarity Assessment-Best Practices, Decision Trees and Global Harmonization

During the write-up of the meeting summary reports from the 2019 dissolution similarity workshop held at the University of Maryland's Center of Excellence in Regulatory Science and Innovation (M-CERSI), several coauthors continued their discussions to develop a "best-practice" document defining the steps required to assess dissolution profiles in support of certain biowaivers and postapproval changes. In previous reports, current challenges related to dissolution profile studies were discussed such that the steps outlined in the two flow charts ("decision trees") presented here can be applied. These decision trees include both recommendations for the use of equivalence procedures between reference and test products as well as application of the dissolution safe space concept. Common approaches towards establishing dissolution safe spaces are described. This paper encourages the preparation of protocols clearly describing why and how testing is performed along with the expected pass/fail criteria prior to generating data on the materials to be evaluated. The target audience of this manuscript includes CMC regulatory scientists, laboratory analysts, as well as statisticians from industry and regulatory health agencies involved in the assessment of product quality via in vitro dissolution testing. Building upon previous publications, this manuscript provides a solution to the current ambiguity related to dissolution profile comparison. The principles outlined in this and previous manuscripts provide a basis for global regulatory alignment in the application of dissolution profile assessment to support manufacturing changes and biowaiver requests.

Detecting Crystallinity in Amorphous Solid Dispersions Using Dissolution Testing: Considerations on Properties of Drug Substance, Drug Product, and Selection of Dissolution Media

Dissolution testing has long been used to monitor product quality. Its role in quality control of amorphous solid dispersion (ASD) formulations is relatively new. In the presence of the crystalline phase, the dissolution of ASDs is determined by the dynamics between the dissolution rate of the amorphous solids and the rate of crystal growth. The detection of crystalline phase by dissolution test has not been well understood in the context of drug properties, formulation characteristics and dissolution test variables. This study systematically evaluated the impact of key parameters such as intrinsic crystallization tendency of the API, drug loading, extent of dissolution sink conditions and level of crystallinity on the ASD dissolution behavior. The results indicated diverse dissolution behaviors due to the differences in the intrinsic crystallization propensity of the drug, the drug loading, the ASD polymers and the dissolution sink index. Each of the complex dissolution profiles were interpreted based on visual observations during dissolution, the appropriate sink index based on the amorphous solubility, and the competition between drug dissolution versus crystallization. The findings of this study provide insights towards the various considerations that should be taken into account towards rationally developing a discriminatory dissolution method.

Characterizing the Physicochemical Properties of Two Weakly Basic Drugs and the Precipitates Obtained from Biorelevant Media

Generally, some weakly basic insoluble drugs will undergo precipitate and redissolution after emptying from the stomach to the small intestinal, resulting in the limited ability to predict the absorption characteristics of compounds in advance. Absorption is determined by the solubility and permeability of compounds, which are related to physicochemical properties, while knowledge about the absorption of redissolved precipitate is poorly documented. Considering that biorelevant media have been widely used to simulate gastrointestinal fluids, sufficient precipitates can be obtained in biorelevant media in vitro. Herein, the purpose of this manuscript is to evaluate the physicochemical properties of precipitates obtained from biorelevant media and active pharmaceutical ingredients (API), and then to explore the potential absorption difference between API and precipitates. Precipitates can be formed by the interaction between compounds and intestinal fluid contents, leading to changes in the crystal structure, melting point, and melting process. However, the newly formed crystals have some advantageous properties compared with the API, such as the improved dissolved rate and the increased intrinsic dissolution rate. Additionally, the permeability of some precipitates obtained from biorelevant media was different from API. Meanwhile, the permeability of rivaroxaban and Drug-A was decreased by 1.92-fold and 3.53-fold, respectively, when the experiments were performed in a biorelevant medium instead of a traditional medium. Therefore, the absorption of precipitate may differ from that of API, and the permeability assay in traditional medium may be overestimated. Based on the research results, it is crucial to understand the physicochemical properties of precipitates and API, which can be used as the departure point to improve the prediction performance of absorption.

Refining the in vitro release test method for a dapivirine-releasing vaginal ring to match in vivo performance

Previously reported in vitro release test methods for drug-releasing vaginal rings containing poorly water-soluble drugs have described use of water-alcohol systems or surfactant solutions in efforts to maintain sink conditions. Here, as part of efforts to more closely match in vitro and in vivo release for the 25 mg dapivirine matrix-type silicone elastomer vaginal ring for HIV prevention, we have investigated alternatives to the 1:1 v/v water/isopropanol medium described previously. Specifically, we evaluated dapivirine release from rings into (i) monophasic water/isopropanol mixtures of varying compositions and (ii) biphasic buffer/octanol systems using pH 4.2 and pH 7.0 buffers. The rate and mechanism of dapivirine release were dependent upon the isopropanol concentration in the release medium, in accordance with the observed trend in drug solubility. At 0 and 10% v/v isopropanol concentrations, dapivirine release followed a partition-controlled mechansim. For media containing ≥ 20% v/v isopropanol, in vitro release of dapivirine was significantly increased and obeyed permeation-controlled kinetics. Cumulative release of ~3.5 mg dapivirine over 28 days was obtained using a water isopropanol mixture containing 20% v/v isopropanol, similar to the ~4 mg dapivirine released in vivo. Dapivirine release into the biphasic buffer/octanol system (intended to mimic the fluid/tissue environment in vivo) was constrained by the limited solubility of dapivirine in the buffer component in which the ring resided, such that cumulative dapivirine release was consistently lower than that observed with the 20% v/v isopropanol in water medium. Release into the biphasic system was also pH dependent, in line with dapivirine's pK_a and with potential implications for in vivo release and absorption in women with elevated vaginal pH.

Aqueous Dissolution and Dispersion Behavior of Polyvinylpyrrolidone Vinyl Acetate-based Amorphous Solid Dispersion of Ritonavir Prepared by Hot-Melt Extrusion with and without Added Surfactants

In this study, the lack of complete drug release from amorphous solid dispersions (ASDs), as observed in most published reports, was investigated. ASDs with 20% ritonavir were prepared by HME using polyvinylpyrrolidone vinyl acetate (PVPVA) alone and in combination with 10% poloxamer 407 or Span 20 as carriers. It was established by the film casting technique that ritonavir was molecularly dispersed in formulations, and accelerated stability testing confirmed that extrudates were physically stable. Dissolution of ASDs (100-mg ritonavir equivalent) was performed in 250 mL 0.01 N HCl (pH 2), pH 6.8 phosphate buffer and FeSSIF-V2. Drug concentrations were measured by filtration through 0.45-μm pores and in unfiltered media; the latter gave total amounts of drug present in dissolution media, both as solution and dispersion. Because of low solubility, ritonavir did not dissolve completely in aqueous media. Rather, it formed supersaturated solutions, and the excess drug dispersed in the oily amorphous form with low particle sizes that could crystallize with time. Due to higher drug solubility, the dissolved drug in FeSSIF-V2 was much higher than that in the phosphate buffer. Complete drug release could be observed by accounting for drug both in solution and as phase-separated dispersion. Thus, the present study provides a complete picture of in vitro drug dissolution and dispersion from ASDs.

Biphasic Dissolution as an Exploratory Method During Early Drug Product Development

Dissolution testing is a major tool used to assess a drug product's performance and as a quality control test for solid oral dosage forms. However, compendial equipment and methods may lack discriminatory power and the ability to simulate aspects of in vivo dissolution. Using low buffer capacity media combined with an absorptive phase (biphasic dissolution) increases the physiologic relevance of in vitro testing. The purpose of this study was to use non-compendial and compendial dissolution test conditions to evaluate the in vitro performance of different formulations. The United States Pharmacopeia (USP)-recommended dissolution method greatly lacked discriminatory power, whereas low buffer capacity media discriminated between manufacturing methods. The use of an absorptive phase in the biphasic dissolution test assisted in controlling the medium pH due to the drug removal from the aqueous medium. Hence, the applied non-compendial methods were more discriminative to drug formulation differences and manufacturing methods than conventional dissolution conditions. In this study, it was demonstrated how biphasic dissolution and a low buffer capacity can be used to assess in vitro drug product performance differences. This can be a valuable approach during the early stages of drug product development for investigating in vitro drug release with improved physiological relevance.

Developing Clinically Relevant Dissolution Specifications for Oral Drug Products-Industrial and Regulatory Perspectives

A meeting that was organized by the Academy of Pharmaceutical Sciences Biopharmaceutics and Regulatory Sciences focus groups focused on the challenges of Developing Clinically Relevant Dissolution Specifications (CRDS) for Oral Drug Products. Industrial Scientists that were involved in product development shared their experiences with in vitro dissolution and in silico modeling approaches to establish clinically relevant dissolution specifications. The regulators shared their perspectives on the acceptability of these different strategies for the development of acceptable specifications. The meeting also reviewed several collaborative initiatives that were relevant to regulatory biopharmaceutics. Following the scientific presentations, a roundtable session provided an opportunity for delegates to discuss the information that was shared during the presentations, debate key questions, and propose strategies to make progress in this critical area of regulatory biopharmaceutics. It was evident from the presentations and subsequent discussions that progress continues to be made with approaches to establish robust CRDS. Further dialogue between industry and regulatory agencies greatly assisted future developments and key areas for focused discussions on CRDS were identified.

In silico Tools at Early Stage of Pharmaceutical Development: Data Needs and Software Capabilities

In early drug development, the selection of a formulation platform and decisions on formulation strategies have to be made within a short timeframe and often with minimal use of the active pharmaceutical ingredient (API). The current work evaluated the various physicochemical parameters required to improve the prediction accuracy of simulation software for immediate release tablets in early drug development. DDDPlus™ was used in simulating dissolution test profiles of immediate release tablets of ritonavir and all simulations were compared with experimental results. The minimum data requirements to make useful predictions were assessed using the ADMET predictor (part of DDDPlus) and Chemicalize (an online resource). A surfactant model was developed to estimate the solubility enhancement in media containing surfactant and the software's transfer model based on the USP two-tiered dissolution test was assessed. One measured data point was shown to be sufficient to make predictive simulations in DDDPlus. At pH 2.0, the software overestimated drug release while at pH 1.0 and 6.8, simulations were close to the measured values. A surfactant solubility model established with measured data gave good dissolution predictions. The transfer model uses a single-vessel model and was unable to predict the two in vivo environments separately. For weak bases like ritonavir, a minimum of three solubility data points is recommended for in silico predictions in buffered media. A surfactant solubility model is useful when predicting dissolution behavior in surfactant media and in silico predictions need measured solubility data to be predictive.