Application of a Refined Developability Classification System

A physiologically based biopharmaceutics modeling (PBBM) framework for characterizing formulation-dependent food effects: Paving the road towards fed state virtual BE studies for itraconazole amorphous solid dispersions

This study leverages physiologically based biopharmaceutics modeling (PBBM) to predict the clinical performance of two itraconazole (ITRA) amorphous solid dispersions (ASDs), Sempera® and Tolsura®, under fasted and fed state conditions, exploring the potential of PBBM in predicting formulation-specific food interactions. The ITRA formulations were subjected to extensive in vitro biopharmaceutical testing, including solubility studies and dissolution tests under fasted and fed state conditions, revealing significant differences in dissolution behaviors between Sempera® and Tolsura®. The impact of food and hypochlorhydria on drug absorption was evaluated using a stepwise mechanistic deconvolution-reconvolution PBBM approach, integrating fundamental parameters based on the in vitro data into the final model. Our model not only successfully predicted the effects of acid reducing agents (ARA) and food on the oral absorption of ITRA, but also captured the between-subject variability, demonstrating the utility of this approach in understanding the complex interplay between drug, formulation, and gastrointestinal environment. Most importantly, the PBBM was able to accurately predict the positive impact of food on the absorption of Sempera® and the negative food effect of Tolsura®. The findings highlight the importance of considering formulation characteristics and gastrointestinal physiology, underscoring the potential of PBBM in bioequivalence (BE) assessment of generic formulations under varying physiological conditions, including in the fed state and in hypochlorhydric patients. The successful application of this stepwise and mechanistic PBBM approach suggests a potential pathway for streamlining drug development and may contribute to more informed decision-making for BE assessment.

Formulation Strategy of BCS-II Drugs by Coupling Mechanistic In-Vitro and Nonclinical In-Vivo Data with PBPK: Fundamentals of Absorption-Dissolution to Parameterization of Modelling and Simulation

BCS class II candidates pose challenges in drug development due to their low solubility and permeability. Researchers have explored various techniques; co-amorphous and solid dispersion are major approaches to enhance in-vitro drug solubility and dissolution. However, in-vivo oral bioavailability remains challenging. Physiologically based pharmacokinetic (PBPK) modeling with a detailed understanding of drug absorption, distribution, metabolism, and excretion (ADME) using a mechanistic approach is emerging. This review summarizes the fundamentals of the PBPK, dissolution-absorption models, parameterization of oral absorption for BCS class II drugs, and provides information about newly emerging artificial intelligence/machine learning (AI/ML) linked PBPK approaches with their advantages, disadvantages, challenges and areas of further exploration. Additionally, the fully integrated workflow for formulation design for investigational new drugs (INDs) and virtual bioequivalence for generic molecules falling under BCS-II are discussed.

Biowaiver monographs for immediate-release solid oral dosage forms: Lemborexant

Lemborexant is a dual orexin receptor antagonist assigned to class II of the Biopharmaceutics Classification System (BCS). Thus, the ICH M9 Guideline excludes immediate-release (IR) solid oral dosage forms containing lemborexant from BCS-based biowaivers, irrespective of their in vitro dissolution behavior. By contrast, classification of lemborexant according to the refined Developability Classification System (rDCS) falls into class I, indicating few biopharmaceutics risks. Customized rDCS investigations identify dissolution as the main risk factor, in line with clinical data in humans which suggest that the absorption of lemborexant is limited neither by solubility nor by permeability. Instead, any risks lie in dissolution. Analysis by the rDCS coupled with biorelevant dissolution testing thus provides a way forward for manufacturers to mitigate the risks associated with changes in formulation or introduction of a generic version prior to running clinical bioequivalence (BE) studies. As a way forward regarding biowaivers for lemborexant and similar cases, where justifying BE based on the current BCS-based approach is not possible, a four-step pathway towards establishing BE virtually could be adopted as follows: (i) rDCS analysis to identify critical bioavailability attributes, (ii) comparative (biorelevant) dissolution testing, (iii) Physiologically Based Biopharmaceutics Modeling (PBBM), and (iv) virtual BE assessment.

Advantages of the refined developability classification system in early discovery

Rat pharmacokinetic studies are commonly utilized in early discovery to support absorption, distribution, metabolism, and excretion optimization of active pharmaceutical ingredients (APIs). The aim of this work was to compare exposures from fit-for-purpose oral suspension and solution formulations in rats to guidance provided by the refined Developability Classification System (rDCS) with respect to identifying potential limits to oral absorption, formulation strategy selection, and to optimize oral bioavailability (BA). This investigation utilized six diverse APIs covering a large range of biorelevant solubility, metabolic stability, and oral BA in rats. While results for our model compounds acetaminophen, voriconazole, fedratinib, lemborexant, and istradefylline indicated oral BA in rats was limited by first-pass metabolism, only the results for voxelotor indicated an oral absorption limitation by intestinal dissolution/solubility. The in vivo studies highlighted challenges and limitations often encountered in early discovery. The rDCS analysis provided a more differentiated developability risk assessment associated with oral solid dosage form development by incorporating compound-specific physicochemical attributes and human physiology without the need of preclinical data. The rDCS results were shown to align well with the clinical/marketed formulation strategies for the investigated APIs.

Biowaiver monographs for immediate-release solid oral dosage forms: Voriconazole

According to the ICH M9 Guideline, the triazole antifungal voriconazole is a Biopharmaceutics Classification System (BCS) class II drug, being highly soluble at the highest dose strength but not at the highest single dose. Although the ICH M9 allows for consideration of BCS-based biowaivers in such cases, voriconazole does not meet the additional requirement of dose proportional pharmacokinetics (PK) over the therapeutic dose range. By contrast, if the classification were based on the FDA solubility criteria that were in place prior to ICH M9 (based on the highest dose strength), voriconazole would belong to BCS class I and thus qualify for the BCS-based biowaiver. Since the highest oral dose strength of voriconazole dissolves very rapidly under all BCS conditions, and comparative in vitro dissolution of different tablet formulations aligns with the demonstration of BE in clinical studies, it seems that the ICH Guideline may be unnecessarily restrictive in the case of voriconazole. Therefore, this review discusses potential revisions of eligibility criteria and the extension of biowaiver approvals to encompass a wider range of appropriate drugs. Specifically, a classification system that is more relevant to in vivo conditions, the refined Developability Classification System (rDCS), coupled with biorelevant dissolution testing, may be more applicable to compounds like voriconazole.

Using the refined Developability Classification System (rDCS) to guide the design of oral formulations

The refined Developability Classification System (rDCS) provides a comprehensive animal-free approach for assessing biopharmaceutical risks associated with developing oral formulations. This work demonstrates practical application of a recently advanced rDCS framework guiding formulation design for six diverse active pharmaceutical ingredients (APIs) and compares rDCS classifications with those of the Biopharmaceutics Classification System (BCS). While the BCS assigns five of the APIs to class II/IV, indicating potentially unfavorable biopharmaceutical attributes, the rDCS provides a more nuanced risk assessment. Both BCS and rDCS assign acetaminophen to class I at therapeutic doses. Voriconazole and lemborexant (both BCS II) are classified in rDCS class I at therapeutic doses, indicating suitability for development as conventional oral formulations. Fedratinib is classified as BCS IV but the rDCS indicates a stratified risk (class I, IIa or IIb), depending on the relevance of supersaturation/precipitation in vivo. Voxelotor and istradefylline (both BCS II) belong to rDCS class IIb, requiring solubility enhancement to achieve adequate oral bioavailability. Comparing the rDCS analysis with literature on development and pharmacokinetics demonstrates that the rDCS reliably supports oral formulation design over a wide range of API characteristics, thus providing a strong foundation for guiding development.

A Stratified Analysis of Supersaturation and Precipitation Effects Based on the Refined Developability Classification System (rDCS)

Supersaturation and precipitation within the gastrointestinal tract can influence oral absorption of active pharmaceutical ingredients (APIs). Supersaturation of weakly basic APIs upon transfer from the stomach into the small intestine may enhance their absorption, while salt forms of poorly soluble weak acids may generate supersaturated solutions in both stomach and intestine. Likewise, APIs with solubility-limited absorption may be developed as enabling formulations intended to produce supersaturated solutions of the API in the gut. Integrating the supersaturation/precipitation characteristics of the API into the biopharmaceutical risk classification enables comprehensive mapping of potential developability risks and guides formulation selection towards optimizing oral bioavailability (BA). The refined Developability Classification System (rDCS) provides an approach for this purpose. In this work, the rDCS strategy is revisited and a stratified approach integrating the in vitro supersaturation and precipitation behavior of APIs and their formulations is proposed.

Structured solubility behaviour in fed simulated intestinal fluids

Intestinal drug solubility is a key parameter controlling absorption after the administration of a solid oral dosage form. The ability to measure fed state solubility in vitro is limited and multiple simulated intestinal fluid recipes have been developed but with no consensus which is optimal. This study has utilised nine bioequivalent simulated fed intestinal media recipes that cover over 90% of the compositional variability of sampled fed human intestinal fluid. The solubility of 24 drugs (Acidic; furosemide, ibuprofen, indomethacin, mefenamic acid, naproxen, phenytoin, piroxicam, valsartan, zafirlukast: Basic; aprepitant, atazanavir, bromocriptine, carvedilol, dipyridamole, posaconazole, tadalafil: Neutral; acyclovir, carbamazepine, felodipine, fenofibrate, griseofulvin, itraconazole, paracetamol, probucol) has been assessed to determine if structured solubility behaviour is present. The measured solubility behaviour can be split into four categories and is consistent with drug physicochemical properties and previous solubility studies. For acidic drugs (category 1) solubility is controlled by media pH and the lowest and highest pH media identify the lowest and highest solubility in 90% of cases. For weakly acidic, basic and neutral drugs (category 2) solubility is controlled by media pH and total amphiphile concentration (TAC), a consistent solubility pattern is evident with variation related to individual drug media component interactions. The lowest and highest pH × TAC media identify the lowest and highest solubility in 70% and 90% of cases respectively. Four drugs, which are non-ionised in the media systems (category 3), have been identified with a very narrow solubility range, indicating minimal impact of the simulated media on solubility. Three drugs exhibit solubility behaviour that is not consistent with the remainder (category 4). The results indicate that the use of two bioequivalent fed intestinal media from the original nine will identify in vitro the maximum and minimum solubility values for the majority of drugs and due to the media derivation this is probably applicable in vivo. When combined with a previous fasted study, this introduces interesting possibilities to measure a solubility range in vitro that can provide Quality by Design based decisions to rationalise drug and formulation development. Overall this indicates that the multi-dimensional media system is worthy of further investigation as in vitro tool to assess fed intestinal solubility.

Leveraging the use of in vitro and computational methods to support the development of enabling oral drug products: An InPharma commentary

Due to the strong tendency towards poorly soluble drugs in modern development pipelines, enabling drug formulations such as amorphous solid dispersions, cyclodextrins, co-crystals and lipid-based formulations are frequently applied to solubilize or generate supersaturation in gastrointestinal fluids, thus enhancing oral drug absorption. Although many innovative in vitro and in silico tools have been introduced in recent years to aid development of enabling formulations, significant knowledge gaps still exist with respect to how best to implement them. As a result, the development strategy for enabling formulations varies considerably within the industry and many elements of empiricism remain. The InPharma network aims to advance a mechanistic, animal-free approach to the assessment of drug developability. This commentary focuses current status and next steps that will be taken in InPharma to identify and fully utilize 'best practice' in vitro and in silico tools for use in physiologically based biopharmaceutic models.

Projection of Target Drug Particle Size in Oral Formulations Using the Refined Developability Classification System (rDCS)

Dissolution limitations to oral absorption can occur if the time required for dissolution is longer than the transit time across the small intestine and/or if dissolution is slower than the drug's permeation through the gut wall. These limitations most often occur for poorly soluble drugs. A standard method for overcoming dissolution issues is to reduce the particle size of the (solid) drug. Building on the refined Developability Classification System (rDCS), this work establishes a novel set of equations with which the appropriate degree of particle size reduction needed to mitigate dissolution limitations to absorption can be calculated. According to the type of data available, the appropriate equation(s) for each situation can be applied. Three case examples are used to illustrate implementation of the equations: voriconazole, lemborexant and istradefylline. Although for voriconazole (rDCS Class I) target radius (r_target) estimates indicate that particle size reduction is unnecessary, for lemborexant (rDCS Class I) a radius of ≤20 µm would be required to improve absorption. For istradefylline (rDCS Class IIb) the r_target was approximately 12 µm. Results are commensurate with literature information for these three drugs, signaling that the equations are suitable for application to a wide variety of drug substances.

Non-Effective Improvement of Absorption for Some Nanoparticle Formulations Explained by Permeability under Non-Sink Conditions

We evaluated the in vitro permeability of nanoparticle formulations of high and low lipophilic compounds under non-sink conditions, wherein compounds are not completely dissolved. The permeability of the highly lipophilic compound, griseofulvin, was improved by about 30% due to nanonization under non-sink conditions. Moreover, this permeability was about 50% higher than that under sink conditions. On the other hand, for the low lipophilic compound, hydrocortisone, there was no difference in permeability between micro-and nano-sized compounds under non-sink conditions. The nanonization of highly lipophilic compounds improves the permeability of the unstirred water layer (UWL), which in turn improves overall permeability. On the other hand, because the rate-limiting step in permeation for the low lipophilic compounds is the diffusion of the compounds in the membrane, the improvement of UWL permeability by nanonization does not improve the overall permeability. Based on this mechanism, nanoparticle formulations are not effective for low lipophilic compounds. To accurately predict the absorption of nanoparticle formulations, it is necessary to consider their permeability under non-sink conditions which reflect in vivo conditions.

Hydroxypropyl Cellulose for Drug Precipitation Inhibition: From the Potential of Molecular Interactions to Performance Considering Microrheology

There has been recent interest in using hydroxypropyl cellulose (HPC) for supersaturating drug formulations. This study investigated the potential for molecular HPC interactions with the model drug celecoxib by integrating novel approaches in the field of drug supersaturation analysis. Following an initial polymer characterization study, quantum-chemical calculations and molecular dynamics simulations were complemented with results of inverse gas chromatography and broadband diffusing wave spectroscopy. HPC performance was studied regarding drug solubilization and kinetics of desupersaturation using different grades (i.e., HPC-UL, SSL, SL, and L). The results suggested that the potential contribution of dispersive interactions and hydrogen bonding depended strongly on the absence or presence of the aqueous phase. It was proposed that aggregation of HPC polymer chains provided a complex heterogeneity of molecular environments with more or less excluded water for drug interaction. In precipitation experiments at a low aqueous polymer concentration (i.e., 0.01%, w/w), grades L and SL appeared to sustain drug supersaturation better than SSL and UL. However, UL was particularly effective in drug solubilization at pH 6.8. Thus, a better understanding of drug-polymer interactions is important for formulation development, and polymer blends may be used to harness the combined advantages of individual polymer grades.

Comparison of Predictions by BCS, rDCS and Machine Learning for the Effect of Food on Oral Drug Absorption Based on Features Calculated In silico

In this study, observed food effects of 473 drugs were categorized into positive, negative, or no effects and compared with the predictions made by machine learning (ML), the Biopharmaceutics Classification System (BCS) and refined Developability Classification System (rDCS). All methods used primarily in silico estimates for prediction, and for ML, four algorithms were evaluated using nested cross-validation to select important information from 371 features calculated based on the chemical structure. Approximately 18 features, including estimated solubility in biorelevant media, were selected as important, and the random forest classifier was the best among four algorithms with 36.6% error rate (ER) and 10.8% opposite prediction rate (OPR). The prediction by rDCS utilizing solubility in a biorelevant medium was somewhat inferior, but not by much; 41.0% ER and 11.4% OPR. Compared with these two methods, the prediction by BCS was inferior; 54.5% ER and 21.4% OPR. ER was improved modestly by using measured features instead of in silico estimates when BCS was applied to a subset of 151 drugs (46.4% from 55.0%). ML and rDCS predicted the food effects of the same subset using in silico estimates with ERs of 37.7% and 42.4%, respectively, suggesting that the predictions by ML and rDCS using in silico features are similar or more accurate than those by BCS using measured features. These results suggest that ML was useful in revealing essential features from complex information and, together with rDCS, is effective in predicting food effects during drug development, including early drug discovery.

A Fine-Tuned Lipophilicity/Hydrophilicity Ratio Governs Antibacterial Potency and Selectivity of Bifurcated Halogen Bond-Forming NBTIs

Herein, we report the design of a focused library of novel bacterial topoisomerase inhibitors (NBTIs) based on innovative mainly monocyclic right-hand side fragments active against DNA gyrase and Topo IV. They exhibit a very potent and wide range of antibacterial activity, even against some of the most concerning hard-to-treat pathogens for which new antibacterials are urgently needed, as reported by the WHO and CDC. NBTIs enzyme activity and whole cell potency seems to depend on the fine-tuned lipophilicity/hydrophilicity ratio that governs the permeability of those compounds through the bacterial membranes. Lipophilicity of NBTIs is apparently optimal for passing through the membrane of Gram-positive bacteria, but the higher, although not excessive lipophilicity and suitable hydrophilicity seems to determine the passage through Gram-negative bacterial membranes. However, due to the considerable hERG inhibition, which is still at least two orders of magnitude away from MICs, continued optimization is required to realize their full potential.

Dose-Dependent Solubility-Permeability Interplay for Poorly Soluble Drugs under Non-Sink Conditions

We investigated the solubility-permeability interplay using a solubilizer additive under non-sink conditions. Sodium lauryl sulfate (SLS) was used as a solubilizer additive. The solubility and permeability of two poorly soluble drugs at various doses, with or without SLS, were evaluated by flux measurements. The total permeated amount of griseofulvin, which has high permeability, increased by the addition of SLS. On the other hand, triamcinolone, which has low permeability, showed an almost constant rate of permeation regardless of the SLS addition. The total permeated amount of griseofulvin increased by about 20-30% when the dose amount exceeded its solubility, whereas its concentration in the donor chamber remained almost constant. However, the total permeated amount of triamcinolone was almost constant regardless of dose amount. These results suggest that the permeability of the unstirred water layer (UWL) may be affected by SLS and solid drugs for high-permeable drugs. The effect of solid drugs could be explained by a reduction in the apparent UWL thickness. For the appropriate evaluation of absorption, it would be essential to consider these effects.

Potent and Selective Human Prostaglandin F (FP) Receptor Antagonist (BAY-6672) for the Treatment of Idiopathic Pulmonary Fibrosis (IPF)

Idiopathic pulmonary fibrosis (IPF) is a rare and devastating chronic lung disease of unknown etiology. Despite the approved treatment options nintedanib and pirfenidone, the medical need for a safe and well-tolerated antifibrotic treatment of IPF remains high. The human prostaglandin F receptor (hFP-R) is widely expressed in the lung tissue and constitutes an attractive target for the treatment of fibrotic lung diseases. Herein, we present our research toward novel quinoline-based hFP-R antagonists, including synthesis and detailed structure-activity relationship (SAR). Starting from a high-throughput screening (HTS) hit of our corporate compound library, multiple parameter improvements-including increase of the relative oral bioavailability F_rel from 3 to ≥100%-led to a highly potent and selective hFP-R antagonist with complete oral absorption from suspension. BAY-6672 (46) represents-to the best of our knowledge-the first reported FP-R antagonist to demonstrate in vivo efficacy in a preclinical animal model of lung fibrosis, thus paving the way for a new treatment option in IPF.

Physiologically based pharmacokinetic model outputs depend on dissolution data and their input: Case examples glibenclamide and dipyridamole

A plethora of dissolution tests exists for oral dosage forms, with variations in selection of the dissolution medium, the hydrodynamics and the dissolution equipment. This work aimed at determining the influence of media composition, the type of dissolution test and the method for entering the data into a PBPK model on the ability to simulate the in vivo plasma profile of an immediate release formulation. Using two rDCS IIa substances, glibenclamide and dipyridamole, housed in immediate-release formulations as model dosage forms, dissolution tests were performed in USP apparatus II with the biorelevant media FaSSGF, FaSSIF V1, V2 and V3 using both single-stage and two-stage test designs. The results were then integrated into the PBPK software Simcyp^Ⓡ either as the observed release profile (dissolution rate model, DRM) or using a semi-mechanistic model (diffusion layer model, DLM) and compared with in vivo plasma profiles. The selection of the FaSSIF version did not appear to have any relevant influence on the dissolution of the weakly basic dipyridamole, while the weakly acidic glibenclamide was sensitive to the difference in pH between FaSSIF V1, V2 and FaSSIF V3. Since both compounds have pKa values close to the pH of biorelevant media representing conditions in the small intestine, these results may be specific to compounds with similar ionization behavior. Single-stage and two-stage testing led to equivalent simulations for glibenclamide. Only results from the single-stage test in FaSSGF led to a close simulation of the pharmacokinetic profile of dipyridamole when data were inputted using the DRM, while simulations from two-stage testing were most similar to the observed pharmacokinetic profile when DLM with selection of a dynamic pH profile in the small intestine was selected as the data input method. These results emphasize the importance of data input to the simulation results.

Selection of In Vivo Predictive Dissolution Media Using Drug Substance and Physiological Properties

The rate and extent of drug dissolution in the gastrointestinal (GI) tract are highly dependent upon drug physicochemical properties and GI fluid properties. Biorelevant dissolution media (BDM), which aim to facilitate in vitro prediction of in vivo dissolution performance, have evolved with our understanding of GI physiology. However, BDM with a variety of properties and compositions are available, making the choice of dissolution medium challenging. In this tutorial, we describe a simple and quantitative methodology for selecting practical, yet physiologically relevant BDM representative of fasted humans for evaluating dissolution of immediate release formulations. Specifically, this methodology describes selection of pH, buffer species, and concentration and evaluates the importance of including bile salts and phospholipids in the BDM based upon drug substance log D, pK_a, and intrinsic solubility. The methodology is based upon a mechanistic understanding of how three main factors affect dissolution, including (1) drug ionization at gastrointestinal pH, (2) alteration of surface pH by charged drug species, and (3) drug solubilization in mixed lipidic aggregates comprising bile salts and phospholipids. Assessment of this methodology through testing and comparison with literature reports showed that the recommendations correctly identified when a biorelevant buffer capacity or the addition of bile salts and phospholipids to the medium would appreciably change the drug dissolution profile. This methodology can enable informed decisions about when a time, complexity, and/or cost-saving buffer is expected to lead to physiologically meaningful in vitro dissolution testing, versus when a more complex buffer would be required.