Measurement of in vivo Gastrointestinal Release and Dissolution of Three Locally Acting Mesalamine Formulations in Regions of the Human Gastrointestinal Tract

The Global Bioequivalence Harmonisation Initiative (GBHI): Report of the sixth international EUFEPS/PQRI conference

At the 6th International Conference of the Global Bioequivalence Harmonisation Initiative (GBHI), co-organised by the European Federation of Pharmaceutical Sciences (EUFEPS) and the Product Quality Research Institute (PQRI), critical bioequivalence (BE) topics were discussed by pharmaceutical scientists from academia, industry and regulatory agencies, revealing the following main conclusions: 1) Physiologically based pharmacokinetic/biopharmaceutic modelling (PBPK/PBBM) for solid oral drugs: PBPK/PBBM gains increasing recognition for generic drug development, e.g. waivers of fed studies and drug interaction studies with proton pump inhibitors. However, especially for complex formulations containing low-solubility compounds, more data are needed for modelling-based conclusion regarding BE in fed state. 2) Narrow therapeutic index drugs: A progress towards harmonisation of BE criteria from US-FDA and EMA speakers was made as there is consensus in the usefulness of applying a mixed scale for BE acceptance range depending on variability, via either fully or partially replicated design. Differences still remain regarding variability comparison and the selection of regulatory constant (0.760 vs. 1.05361). All parties confirmed the importance of controlling type-I error. 3) Single- vs. multiple-dose studies for BE demonstration of modified-release (MR) products: To circumvent multiple-dose studies, model-informed approaches were discussed based on real-life data, e.g. to simulate steady-state profiles from single-dose data. To reduce the burden in patient trials for long-acting injectables promising modelling approaches were presented, extrapolating from incomplete steady-state scenarios. 4) BE demonstration for additional dose strengths of solid oral MR products: For multiple-unit dosage forms where strengths differ in number of units only, testing BE of the highest dose was considered sufficient. In addition, there was some consensus that, whenever extrapolation from one strength to the others is not easily established, the "bracket-approach" of the EMA focusing on the intake conditions in the label claim (fasted or fed), can help mitigating risks without adding significant cost and effort. 5) Partial AUC for BE demonstration: Clinical relevance is key to decide on the relevant PK metrics for BE assessment whenever possible. There was consensus that the BE criteria and evaluation strategy may be best specified in product-specific guidances - preferably with international harmonisation. 6) BE of orally inhaled drug products (OIDPs): The "weight-of-evidence" approach of US-FDA and the stepwise approach of EMA largely differ. The auditorium was in favour of combining data on in-vitro characteristics and PK exposure. For prediction of comparable efficacy of two OIDPs, there is good trust in PK exposure data whenever they present concentrations being absorbed via the lung. GBHI has a strong role in scientifically supporting official harmonisation efforts including the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use since the first conference in 2015.

Challenges in Predicting Colonic Luminal and Tissue Concentrations of Mesalamine and Acetyl Mesalamine using Physiologically Based Biopharmaceutics Modeling

Mesalamine is a standard first-line therapy for managing chronic inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. Despite its established efficacy, the precise mechanism of action within enterocytes remains unclear. This study aimed to develop and validate Physiologically Based Biopharmaceutics Models (PBBM) for mesalamine (5-ASA) and its metabolite, acetyl mesalamine (Ac-5-ASA), to predict drug concentrations in plasma, colonic lumen, and colonic tissue of healthy subjects and compare the results to measured concentrations. Using the Simcyp Simulator (V22), the models accurately predicted plasma concentrations for various formulations, including intravenous, oral immediate-release and controlled release formulations within a two-fold range. Results also captured the intestinal and hepatic metabolism converting mesalamine to acetyl mesalamine. However, significant discrepancies were observed in predicting luminal and tissue concentrations, with underpredictions for Claversal and Pentasa formulations reaching factors of up to 506 and 55 for 5-ASA and Ac-5-ASA in colonic tissue, respectively. These discrepancies highlight limitations in current modeling approaches, particularly in simulating drug accumulation within enterocytes. Despite these challenges, this investigation highlights both the potential benefits and the complexities of using PBBMs. Future work should focus on generating definitive N-acetyl transferase (NAT1) abundance data with an in-vitro in-vivo extrapolation link, improving approaches to better explore local drug concentrations in the gastrointestinal tract, and addressing the gap in accurately predicting luminal and tissue concentrations in the colon.

Exploration of the potential impact of batch-to-batch variability on the establishment of pharmacokinetic bioequivalence for inhalation powder drug products

Batch-to-batch variability in inhalation powder has been identified as a potential challenge in the development of generic versions. This study explored the impact of batch-to-batch variability on the probability of establishing pharmacokinetic (PK) bioequivalence (BE) in a two-sequence, two-period (2 × 2) crossover study. A model-based parametric simulation approach was employed, incorporating batch-to-batch variability through the relative bioavailability (RBA) ratio. In the absence of batch variability, recruiting a total of 48 subjects in a 2 × 2 crossover study with the reference formulation resulted in a 95% probability of concluding BE. However, this probability decreased to 80% with a 5% batch difference in RBA and further declined to 30% with a 10% batch difference. With a 10% batch difference, the required number of subjects to achieve an 80% probability of concluding BE increased to 84. When considering product differences between the reference and the test formulations, an additional 10% batch difference reduced the study power from 97% to 30% for a T/R bioavailability ratio of 100% in a 2 × 2 crossover study with 48 subjects. As a result, the substantial impact of batch-to-batch variability on the study power and type I error of the PK BE study may pose significant challenges for the development of generic Advair Diskus due to its degree of PK batch-to-batch variability. Therefore, alternative PK BE study designs and guidelines are needed to adequately address the influence of batch-to-batch variability in products like Advair Diskus.

5-Aminosalicylic Acid Distribution into the Intestinal Membrane Along the Gastrointestinal Tract After Oral Administration in Rats

BACKGROUND

5-Aminosalicylic acid (5-ASA), the first-line therapy for ulcerative colitis, is a poorly soluble zwitterionic drug. Unformulated 5-ASA is thought to be extensively absorbed in the small intestine.

METHODS

The pH-dependent solubility of 5-ASA in vitro and the intestinal membrane distribution of 5-ASA and its N-acetyl metabolite (AC-5-ASA) after the oral administration of 5-ASA were examined in fed rats. 5-ASA was administered as a suspension in water, 0.1 M HCl, or 0.1 M NaOH to untreated rats or as a solution in 5% NaHCO3 to lansoprazole-pretreated rats.

RESULTS

5-ASA solubility in vitro was higher at pH < 2 and pH > 7. In rats, the 5-ASA and AC-5-ASA were detected mostly in the small intestine at 3 h and in the colonic region at 8 h after administration. The dosing vehicle (suspension or solution) and lansoprazole pretreatment did not significantly affect the pH of the luminal fluid in rats or the 5-ASA distribution in membranes.

CONCLUSIONS

The 5-ASA distribution in membranes in the proximal intestine was found to be restricted by the intrinsic regional luminal pH, low solubility, and saturable membrane permeability. Unabsorbed 5-ASA in the proximal intestine was delivered to the distal intestine. The higher the oral dose of 5-ASA, the more 5-ASA may be delivered to the distal intestine due to the restricted absorption in the small intestine.

Physiologically Based Biopharmaceutics Modeling Coupled with Biopredictive Dissolution in Development of Bioequivalent Formulation for Mesalamine Enteric Coated Tablet: A Tough Nut to Crack

Mesalamine is a locally acting anti-inflammatory drug used to treat mild to moderate ulcerative colitis. Because of complex formulation principle and high in vivo variability, development of bioequivalent formulation for mesalamine is challenging. Further, fed state possess significant challenges for bioequivalence (BE) due to interplay of multiple factors. In the work, we have developed a novel biopredictive media for mesalamine enteric coated tablets and integrated into physiologically based biopharmaceutics model (PBBM) to predict in vivo fed behavior. USP III based gradient media was developed to mimic in vivo fed condition. The developed PBBM was initially validated with literature data and subsequently re-optimized with pilot BE study data. Further, virtual bioequivalence (VBE) was performed to evaluate model predictability for pilot BE data. Later, the model was applied for prospective BE predictions with increased subjects and parametric sensitivity analysis was performed to identify physiological factors that can impact in vivo performance. Further, the model was used to predict luminal and enterocyte concentrations in colon to demonstrate equivalent efficacy. Additionally, a novel dissolution/permeation tool (Dissoflux) was employed to compare permeability behavior of formulations. Overall, this work enabled BE prediction for complex mesalamine enteric coated tablets and helped to understand parameters that can impact in vivo performance.

State-of-the-art and future perspectives in ingestible remotely controlled smart capsules for drug delivery: A GENEGUT review

An emerging concern globally, particularly in developed countries, is the rising prevalence of Inflammatory Bowel Disease (IBD), such as Crohn's disease. Oral delivery technologies that can release the active therapeutic cargo specifically at selected sites of inflammation offer great promise to maximise treatment outcomes and minimise off-target effects. Therapeutic strategies for IBD have expanded in recent years, with an increasing focus on biologic and nucleic acid-based therapies. Reliable site-specific delivery in the gastrointestinal (GI) tract is particularly crucial for these therapeutics to ensure sufficient concentrations in the targeted cells. Ingestible smart capsules hold great potential for precise drug delivery. Despite previous unsuccessful endeavours to commercialise drug delivery smart capsules, the current rise in demand and recent advancements in component development, manufacturing, and miniaturisation have reignited interest in ingestible devices. Consequently, this review analyses the advancements in various mechanical and electrical components associated with ingestible smart drug delivery capsules. These components include modules for device localisation, actuation and retention within the GI tract, signal transmission, drug release, power supply, and payload storage. Challenges and constraints associated with previous capsule design functionality are presented, followed by a critical outlook on future design considerations to ensure efficient and reliable site-specific delivery for the local treatment of GI disorders.

MMX mesalamine in ulcerative colitis: Major advantages towards classical mesalamine formulations

Medical therapy is the cornerstone of ulcerative colitis (UC) management and aims to induce and maintain remission. In case of mild-to-moderate UC, mesalamine (5-ASA) is the first-line option. 5-ASA requires local release at the level of the inflamed mucosa to exert its therapeutic action. While rectal preparations are useful in distal colitis, in cases of UC of at least rectosigmoid extent, guidelines suggest the association of oral and rectal 5-ASA. Mesalamine with Multi Matrix System® technology (MMX mesalamine) is an oral, high-strength (1.2 g/tablet), once-daily formulation of 5-ASA, designed to provide delayed and prolonged release throughout the entire colon. Clinical trials demonstrated a strong efficacy in inducing and maintaining clinical and endoscopic remission in active mild-to-moderate UC. The efficacy is related to specific colonic drug-delivery, to its high-dosage and once-daily administration, thus improving patients' adherence and outcomes. The specific colonic-delivery is also associated with very low rates of systemic absorption and adverse events (AEs). With this comprehensive review we aimed to summarize current knowledge on MMX mesalamine in mild-to-moderate UC, in terms of clinical pharmacology, efficacy and safety, also compared to other 5-ASA products. In addition we provided an expert opinion on the topic, examining the implications on clinical practice.

Physiologically Based Biopharmaceutics Model (PBBM) of Minimally Absorbed Locally Acting Drugs in the Gastrointestinal Tract-Case Study: Tenapanor

A physiologically based biopharmaceutics model (PBBM) was developed to predict stool and urine sodium content in response to tenapanor administration in healthy subjects. Tenapanor is a minimally absorbed small molecule that inhibits the sodium/hydrogen isoform 3 exchanger (NHE3). It is used to treat irritable bowel syndrome with constipation (IBS-C). Its mode of action in the gastrointestinal tract reduces the uptake of sodium, resulting in an increase in water secretion in the intestinal lumen and accelerating intestinal transit time. The strategy employed was to perform drug-drug interaction (DDI) modelling between sodium and tenapanor, with sodium as the "victim" administered as part of daily food intake and tenapanor as the "perpetrator" altering sodium absorption. Food effect was modelled, including meal-induced NHE3 activity using sodium as an inducer by normalising the induction kinetics of butyrate to sodium equivalents. The presented model successfully predicted both urine and stool sodium content in response to tenapanor dosed in healthy subjects (within 1.25-fold error) and provided insight into the clinical observations of tenapanor dosing time relative to meal ingestion. The PBBM model was applied retrospectively to assess the impact of different forms of tenapanor (free base vs. HCl salt) on its pharmacodynamic (PD) effect. The developed modelling strategy can be effectively adopted to increase confidence in using PBBM models for the prediction of the in vivo behaviour of minimally absorbed, locally acting drugs in the gastrointestinal tract, when other approaches (e.g., biomarkers or PD data) are not available.

Potential of Mesalazine Therapeutic Drug Monitoring by Measuring Fecal Excretion in Patients With Ulcerative Colitis

BACKGROUND

Therapeutic drug monitoring of mesalazine (5-ASA) in patients with ulcerative colitis is unavailable. Mucosal 5-ASA concentrations are assumed to be higher during remission, but biopsy is not practical. Therefore, we investigated the feasibility of measuring mesalazine levels in feces. To explore the potential role of fecal mesalazine measurements in therapeutic drug monitoring, we compared the dry fecal concentration and daily fecal excretion of 5-ASA and its metabolite N-acetyl-5-ASA in patients with ulcerative colitis with active and quiescent disease.

METHODS

Adults with ulcerative colitis on oral mesalazine and scheduled for colonoscopy were eligible for inclusion in this cross-sectional study. Stool and urine samples were collected for 48 and 24 hours, respectively, and rectal biopsies were performed. (N-acetyl-)5-ASA was measured using mass spectrometry. Biochemically active disease was defined as a fecal calprotectin level above 100 mcg/g and endoscopically active disease as any activity following the endoscopic Mayo score (≥1).

RESULTS

Approximately 28 patients were included in the study. Daily fecal excretion of (N-acetyl-)5-ASA did not differ between patients with (n = 13) and without (n = 15) endoscopically active disease [median 572 mg/d versus 597 mg/d ( P = 0.86) for 5-ASA and 572 mg/d versus 554 mg/d ( P = 0.86) for N-acetyl-5-ASA]. The same applied to the fecal concentration [median 9.7 mcg/mg dry weight versus 10.3 ( P = 0.53) and 12.0 versus 9.9 ( P = 0.89)]. The results were comparable when the biochemical disease activity definition was used. The mucosal concentrations and urinary excretion of (N-acetyl-)5-ASA did not differentiate between quiescent and active activity.

CONCLUSIONS

Fecal (N-acetyl-)5-ASA measurements do not correlate with disease activity, which renders it an unsuitable tool for therapeutic drug monitoring of mesalazine.

Current State and Challenges of Physiologically Based Biopharmaceutics Modeling (PBBM) in Oral Drug Product Development

Physiologically based biopharmaceutics modeling (PBBM) emphasizes the integration of physicochemical properties of drug substance and formulation characteristics with system physiological parameters to predict the absorption and pharmacokinetics (PK) of a drug product. PBBM has been successfully utilized in drug development from discovery to postapproval stages and covers a variety of applications. The use of PBBM facilitates drug development and can reduce the number of preclinical and clinical studies. In this review, we summarized the major applications of PBBM, which are classified into six categories: formulation selection and development, biopredictive dissolution method development, biopharmaceutics risk assessment, clinically relevant specification settings, food effect evaluation and pH-dependent drug-drug-interaction risk assessment. The current state of PBBM applications is illustrated with examples from published studies for each category of application. Despite the variety of PBBM applications, there are still many hurdles limiting the use of PBBM in drug development, that are associated with the complexity of gastrointestinal and human physiology, the knowledge gap between the in vitro and the in vivo behavior of drug products, the limitations of model interfaces, and the lack of agreed model validation criteria, among other issues. The challenges and essential considerations related to the use of PBBM are discussed in a question-based format along with the scientific thinking on future research directions. We hope this review can foster open discussions between the pharmaceutical industry and regulatory agencies and encourage collaborative research to fill the gaps, with the ultimate goal to maximize the applications of PBBM in oral drug product development.

Tablet formulation with dual control concept for efficient colonic drug delivery

Aim of this study was to develop a tablet formulation for targeted colonic drug release by implementing two control mechanisms: A pH-sensitive coating layer based on Eudragit® FS 30 D to prevent drug release in the upper gastrointestinal tract, combined with a matrix based on plant-derived polysaccharide xyloglucan to inhibit drug release after coating removal in the small intestine and to allow microbiome triggered drug release in the colon. In vitro dissolution tests simulated the passage through the entire gastrointestinal tract with a four-stage protocol, including microbial xyloglucanase addition in physiologically relevant concentrations as microbiome surrogate to the colonic dissolution medium. Matrix erosion was monitored in parallel to drug release by measurement of reducing sugar equivalents resulting from xyloglucan hydrolysis. Limited drug release in gastric and small intestinal test stages and predominant release in the colonic stage was achieved. The xyloglucan matrix controlled drug release after dissolution of the enteric coating through the formation of a gummy polysaccharide layer at the tablet surface. Matrix degradation was dependent on enzyme concentration in the colonic medium and significantly accelerated drug release resulting in erosion-controlled release process. Drug release at physiologically relevant enzyme concentration was completed within the bounds of colonic transit time. The dual control concept was applicable to two drug substances with different solubility, providing similar release rates in colonic environment containing xyloglucanase. Drug solubility mechanistically affected release, with diffusion of caffeine, but not of 5-ASA, contributing to the overall release rate out of the matrix tablet.

Bioadhesive Tannic-Acid-Functionalized Zein Coating Achieves Engineered Colonic Delivery of IBD Therapeutics via Reservoir Microdevices

The biggest challenge in oral delivery of anti-inflammatory drugs such as 5-aminosalicylic acid (5-ASA) is to (i) prevent rapid absorption in the small intestine and (ii) achieve localized release at the site of inflammation in the lower gut, i.e., the colon. Here, we present an advanced biopolymeric coating comprising of tannic-acid-functionalized zein protein to provide a sustained, colon-targeted release profile for 5-ASA and enhance the mucoadhesion of the dosage form via a mussel-inspired mechanism. To enable localized delivery and provide high local concentration, 5-ASA is loaded into the microfabricated drug carriers (microcontainers) and sealed with the developed coating. The functionality and drug release profile of the coating are characterized and optimized in vitro, showing great tunability, scalability, and stability toward proteases. Further, ex vivo experiments demonstrate that the tannic acid functionalization can significantly enhance the mucoadhesion of the coating, which is followed up by in vivo investigations on the intestinal retention, and pharmacokinetic evaluation of the 5-ASA delivery system. Results indicate that the developed coating can provide prolonged colonic delivery of 5-ASA. Therefore, the here-developed biodegradable coating can be an eco-friendly substitute to the state-of-the-art commercial counterparts for targeted delivery of 5-ASA and other small molecule drugs.

The effect of esomeprazole on the upper GI tract release and systemic absorption of mesalazine from colon targeted formulations

The aim of the present study was to investigate the effect of coadministration of the proton pump inhibitor (PPI) esomeprazole on the upper GI tract behavior and systemic exposure of mesalazine from two mechanistically different colon targeted delivery systems: Claversal (pH-dependent release) and Pentasa (prolonged release). To this end, gastric, jejunal and systemic concentrations of mesalazine and its metabolite N-acetyl mesalazine were monitored in 5 healthy volunteers following oral intake of Pentasa or Claversal with or without PPI pre-treatment (cross-over study). Our exploratory study demonstrated that pre-treatment with a PPI may affect the release and absorption of mesalazine from formulations with different modified release mechanisms. Upon intake of Claversal, the onset of mesalazine absorption was accelerated substantially by PPI pre-treatment. While the PPI-induced increase in pH initiated the disintegration process already in the upper GI tract, the release of mesalazine started beyond the proximal jejunum. Upon intake of Pentasa, PPI pre-treatment seemed to increase the systemic exposure, even though the underlying mechanism could not be revealed yet. The faster release of mesalazine in the GI tract and/or the increased systemic absorption following PPI pre-treatment may reduce the ability of mesalazine to reach the colon. Future research assessing mesalazine disposition in the lower GI tract is warranted.

Clinical translation of advanced colonic drug delivery technologies

Targeted drug delivery to the colon offers a myriad of benefits, including treatment of local diseases, direct access to unique therapeutic targets and the potential for increasing systemic drug bioavailability and efficacy. Although a range of traditional colonic delivery technologies are available, these systems exhibit inconsistent drug release due to physiological variability between and within individuals, which may be further exacerbated by underlying disease states. In recent years, significant translational and commercial advances have been made with the introduction of new technologies that incorporate independent multi-stimuli release mechanisms (pH and/or microbiota-dependent release). Harnessing these advanced technologies offers new possibilities for drug delivery via the colon, including the delivery of biopharmaceuticals, vaccines, nutrients, and microbiome therapeutics for the treatment of both local and systemic diseases. This review details the latest advances in colonic drug delivery, with an emphasis on emerging therapeutic opportunities and clinical technology translation.

In Vitro Methodologies for Evaluating Colon-Targeted Pharmaceutical Products and Industry Perspectives for Their Applications

Several locally acting colon-targeted products to treat colonic diseases have been recently developed and marketed, taking advantage of gastrointestinal physiology to target delivery. Main mechanisms involve pH-dependent, time-controlled and/or enzymatic-triggered release. With site of action located before systemic circulation and troublesome colonic sampling, there is room for the introduction of meaningful in vitro methods for development, quality control (QC) and regulatory applications of these formulations. A one-size-fits-all method seems unrealistic, as the selection of experimental conditions should resemble the physiological features exploited to trigger the release. This article reviews the state of the art for bio-predictive dissolution testing of colon-targeted products. Compendial methods overlook physiological aspects, such as buffer molarity and fluid composition. These are critical for pH-dependent products and time-controlled systems containing ionizable drugs. Moreover, meaningful methods for enzymatic-triggered products including either bacteria or enzymes are completely ignored by pharmacopeias. Bio-predictive testing may accelerate the development of successful products, although this may require complex methodologies. However, for high-throughput routine testing (e.g., QC), simplified methods can be used where balance is struck between simplicity, robustness and transferability on one side and bio-predictivity on the other. Ultimately, bio-predictive methods can occupy a special niche in terms of supplementing plasma concentration data for regulatory approval.

Quantification of Fluid Volume and Distribution in the Paediatric Colon via Magnetic Resonance Imaging

Previous studies have used magnetic resonance imaging (MRI) to quantify the fluid in the stomach and small intestine of children, and the stomach, small intestine and colon of adults. This is the first study to quantify fluid volumes and distribution using MRI in the paediatric colon. MRI datasets from 28 fasted (aged 0-15 years) and 18 fluid-fed (aged 10-16 years) paediatric participants were acquired during routine clinical care. A series of 2D- and 3D-based software protocols were used to measure colonic fluid volume and localisation. The paediatric colon contained a mean volume of 22.5 mL ± 41.3 mL fluid, (range 0-167.5 mL, median volume 0.80 mL) in 15.5 ± 17.5 discreet fluid pockets (median 12). The proportion of the fluid pockets larger than 1 mL was 9.6%, which contributed to 94.5% of the total fluid volume observed. No correlation was detected between all-ages and colonic fluid volume, nor was a difference in colonic fluid volumes observed based on sex, fed state or age group based on ICH-classifications. This study quantified fluid volumes within the paediatric colon, and these data will aid and accelerate the development of biorelevant tools to progress paediatric drug development for colon-targeting formulations.

Differential effects of mesalazine formulations on thiopurine metabolism through thiopurine S-methyltransferase inhibition

BACKGROUND AND AIM

Thiopurines are often used in combination with mesalazine for the treatment of ulcerative colitis (UC). Mesalazine formulations are delivered to the digestive tract by various delivery systems and absorbed as 5-aminosalicylic acid (5-ASA). 5-ASA is known to inhibit thiopurine S-methyltransferase (TPMT) activity and to affect thiopurine metabolism. There have been no studies comparing TPMT inhibition by multimatrix mesalazine (MMX) with other formulations. We investigated the difference in TPMT inhibition by different mesalazine formulations and prospectively confirmed the clinical relevance.

METHODS

Plasma concentrations of 5-ASA, N-acetyl-5-aminosalicylic acid (N-Ac-5-ASA), and TPMT activities were measured in UC patients receiving various mesalazine formulations (time-dependent or pH-dependent mesalazine or MMX) as monotherapy. Patients already on both time-dependent or pH-dependent mesalazine and thiopurines switched their mesalazine to MMX, examining 6-thioguanine nucleotide (6-TGN) and 6-methylmercaptopurine (6-MMP) 0 and 8 weeks after switching. Clinical relapse after switching was also monitored for 24 weeks.

RESULTS

Plasma 5-ASA and N-Ac-5-ASA levels were significantly higher in patients receiving time-dependent mesalazine (n = 12) compared with pH-dependent mesalazine (n = 12) and MMX (n = 15), accompanied by greater TPMT inhibition. Prospective switching from time-dependent mesalazine to MMX decreased 6-TGN levels, increased those of 6-MMP, and increased 6-MMP/6-TGN ratios. Furthermore, this resulted in significantly more relapses than switching from pH-dependent mesalazine to MMX.

CONCLUSIONS

Time-dependent mesalazine has higher plasma 5-ASA and N-Ac-5-ASA levels and greater TPMT inhibition than MMX. Therefore, switching from time-dependent mesalazine to MMX may lead to an increase of 6-MMP/6-TGN, which may reduce the clinical effectiveness of thiopurines, warranting close monitoring after switch.

Factors associated with the persistence of oral 5-aminosalicylic acid monotherapy in ulcerative colitis: a nationwide Norwegian cohort study

BACKGROUND

Oral 5-aminosalicylic acid (5-ASA) is the mainstay treatment of ulcerative colitis (UC) and therapy with oral 5-ASA is associated with beneficial outcomes. We have examined factors associated with the persistence of oral 5-ASA treatment in a national cohort of UC patients.

METHODS

Patients with newly diagnosed UC from 2010 to 2014 using oral 5-ASA monotherapy were identified by combining data from the Norwegian Patient Registry and the Norwegian Prescription Database. The median follow-up time was 1029 days. Drug persistence was defined as duration of oral 5-ASA preparation as monotherapy. Non-persistence of a oral 5-ASA preparation as monotherapy was defined as stopping oral 5-ASA, initiation of any further anti-inflammatory treatment including a course of glucocorticoids and a change to another oral 5-ASA preparation. Drug persistence was analyzed using the Kaplan-Meier method and influence of covariates on drug persistence was analyzed with the Cox proportional hazard model.

RESULTS

A total of 3421 patients were identified. The overall median 5-ASA drug persistence was 179 days. In univariate analyses, persistence was associated with preparation type and high-dose treatment, while oral glucocorticoid use or hospitalization around the start of oral 5-ASA were associated with shorter 5-ASA persistence. In multivariate analyses, oral glucocorticoids [HR 1.67 (1.54-1.80), p < 0.005] and hospitalization around start of 5-ASA [HR 1.23 (1.14-1.34), p < 0.005] were associated with non-persistence, whereas high dose (⩾3 g/day) 5-ASA was associated with longer persistence [HR 0.68 (0.65-0.71), p < 0.005].

CONCLUSION

High-dose treatment with oral 5-ASA was associated with longer persistence of oral 5-ASA monotherapy, whereas the presence of factors indicating more severe disease around initiation of 5-ASA monotherapy was associated with a shorter persistence.

Protective effects of sulfated polysaccharide from Enterobacter cloacae Z0206 against DSS-induced intestinal injury via DNA methylation

We previously obtained and characterized a novel sulfated derivative of the exopolysaccharides from Enterobacter cloacae Z0206 (SEPS). This study aimed at investigating the effects and mechanism of SEPS against dextran sulfate sodium (DSS) induced intestinal injury. The results showed that SEPS increased the proliferation and survival of intestinal epithelial cells during DSS stimulation. Furthermore, SEPS maintained the barrier function and inflammatory response via JAK2 and MAPK signaling to protect against DSS-induced intestinal injury. Mechanistically, SEPS elevated the DNA methylation in the promoter region to negatively regulate the JAK2 and MAPKs expression. Thus, the current study shows the potential effects and mechanism of SEPS on DSS-induced intestinal epithelial cell injury.

Use of Partial Area Under the Curve in Bioavailability or Bioequivalence Assessments: A Regulatory Perspective

Peak drug concentration (C_max ) and total exposure, such as area under the concentration-time curve (AUC) from time zero to infinity may be insufficient for assessing relative bioavailability (BA) or bioequivalence (BE) among two products in cases where rapid onset of action or controlled duration of effect is needed to ensure similar drug efficacy. Regulatory agencies have recommended the use of partial AUC (pAUC) as an additional exposure measure for relative BA or BE assessments. The pAUC metric describes pharmacokinetic profiles with the focus on quantification of exposures over specific time intervals to support the determination of relative BA or BE for these drug products in relation to respective reference products. The principles and rationales for using pAUCs are included in the US Food and Drug Administration (FDA)'s general BA or BE guidances. Specific pAUC recommendations are also reflected in product-specific guidances for generic drug development published by the FDA. Rationales for the use of pAUCs in relative BA or BE assessments are based on drug-specific and product-specific considerations. This white paper introduces the general framework, including rationales for pAUC recommendations, and provides an overview of the current status, challenges, and the FDA considerations on the use of pAUC for relative BA or BE assessments in the United States.

Drug Disposition in the Lower Gastrointestinal Tract: Targeting and Monitoring

The increasing prevalence of colonic diseases calls for a better understanding of the various colonic drug absorption barriers of colon-targeted formulations, and for reliable in vitro tools that accurately predict local drug disposition. In vivo relevant incubation conditions have been shown to better capture the composition of the limited colonic fluid and have resulted in relevant degradation and dissolution kinetics of drugs and formulations. Furthermore, drug hurdles such as efflux transporters and metabolising enzymes, and the presence of mucus and microbiome are slowly integrated into drug stability- and permeation assays. Traditionally, the well characterized Caco-2 cell line and the Ussing chamber technique are used to assess the absorption characteristics of small drug molecules. Recently, various stem cell-derived intestinal systems have emerged, closely mimicking epithelial physiology. Models that can assess microbiome-mediated drug metabolism or enable coculturing of gut microbiome with epithelial cells are also increasingly explored. Here we provide a comprehensive overview of the colonic physiology in relation to drug absorption, and review colon-targeting formulation strategies and in vitro tools to characterize colonic drug disposition.

Potential in vivo delivery routes of postbiotics

Bioactive micro- and macro-molecules (postbiotics) derived from gut beneficial microbes are among natural chemical compounds with medical significance. Currently, a unique therapeutic strategy has been developed with an emphasis on the small molecular weight biomolecules that are made by the microbiome, which endow the host with several physiological health benefits. A large number of postbiotics have been characterized, which due to their unique pharmacokinetic properties in terms of controllable aspects of the dosage and various delivery routes, could be employed as promising medical tools since they exert both prevention and treatment strategies in the host. Nevertheless, there are still main challenges for the in vivo delivery of postbiotics. Currently, scientific literature confirms that targeted delivery systems based on nanoparticles, due to their appealing properties in terms of high biocompatibility, biodegradability, low toxicity, and significant capability to carry both hydrophobic and hydrophilic postbiotics, can be used as a novel and safe strategy for targeted delivery or/and release of postbiotics in various (oral, intradermal, and intravenous) in vivo models. The in vivo delivery of postbiotics are in their emerging phase and require massive investigation and randomized double-blind clinical trials if they are to be applied extensively as treatment strategies. This manuscript provides an overview of the various postbiotic metabolites derived from the gut beneficial microbes, their potential therapeutic activities, and recent progressions in the drug delivery field, as well as concisely giving an insight on the main in vivo delivery routes of postbiotics.

New Insights of Oral Colonic Drug Delivery Systems for Inflammatory Bowel Disease Therapy

Colonic Drug Delivery Systems (CDDS) are especially advantageous for local treatment of inflammatory bowel diseases (IBD). Site-targeted drug release allows to obtain a high drug concentration in injured tissues and less systemic adverse effects, as consequence of less/null drug absorption in small intestine. This review focused on the reported contributions in the last four years to improve the effectiveness of treatments of inflammatory bowel diseases. The work concludes that there has been an increase in the development of CDDS in which pH, specific enzymes, reactive oxygen species (ROS), or a combination of all of these triggers the release. These delivery systems demonstrated a therapeutic improvement with fewer adverse effects. Future perspectives to the treatment of this disease include the elucidation of molecular basis of IBD diseases in order to design more specific treatments, and the performance of more in vivo assays to validate the specificity and stability of the obtained systems.

Nanoparticle-Mediated Drug Delivery Systems For The Treatment Of IBD: Current Perspectives

Inflammatory bowel disease (IBD), which mainly consists of Crohn’s disease and ulcerative colitis, is a chronic and relapsing inflammatory condition of the gastrointestinal tract. The traditional treatment strategies relied on frequent administration of high dosages of medications, including antibiotics, non-steroidal anti-inflammatory drugs, biologics, and immunomodulators, with the goal of reducing inflammation. Some of these medications were effective in alleviating the early-stage inflammatory symptoms, but their long-term efficacies were compromised by the accumulation of toxicities. Recently, nanoparticle (NP)-based drugs have been widely studied for their potential to solve such problems. Various mechanisms/strategies, including size-, charge-, pH-, pressure-, degradation-, ligand-receptor-, and microbiome- dependent drug delivery systems, have been exploited in preclinical studies. A certain number of NP delivery systems have sought to target drugs to the inflamed intestine. Although several NP-based drugs have entered clinical trials for the treatment of IBD, most have failed due to premature drug release, weak targeting ability, and the high immune toxicity of some of the synthetic nanomaterials that have been used to fabricate the NPs. Therefore, there is still a need for rationally designed and stable NP drug delivery system that can specifically target drugs to the disease site, prolong the drug’s residence time, and minimize systemic side effects. This review will analyze the current state of the art in NP-mediated drug delivery for IBD treatment. We will focus on topics such as deliverable targets (at the tissue or cellular level) for treating inflammation; the target-homing NP materials that can interact with such targets; and the major administration routes for treating IBD. These discussions will integrate notable trends in the research and development of IBD medications, including multi-responsive NP-mediated delivery and naturally-derived targeting NPs. Finally, current challenges and future directions will be presented in the hopes of advancing the study of NP-mediated strategies for treating IBD.

Mechanistic Deconvolution of Oral Absorption Model with Dynamic Gastrointestinal Fluid to Predict Regional Rate and Extent of GI Drug Dissolution

Multiple approaches such as mathematical deconvolution and mechanistic oral absorption models have been used to predict in vivo drug dissolution in the gastrointestinal (GI) tract. However, these approaches are often validated by plasma pharmacokinetic profiles, but not by in vivo drug dissolution due to the limited data available regarding the local GI environment. It is also challenging to predict and validate in vivo dissolution in different regions of the GI tract (stomach, duodenum, jejunum, and ileum). In this study, the dynamic fluid compartment absorption and transport (DFCAT) model was used to predict the in vivo dissolution profiles of ibuprofen, which was administered as an 800-mg immediate-release tablet to healthy subjects, in different regions of the GI tract. The prediction was validated with concentration time-courses of ibuprofen (BCS class 2a) in different regions of the GI tract that we have obtained over the past few years. The computational model predicted that the dissolution of ibuprofen was minimal in the stomach (2%), slightly more in the duodenum (6.3%), and primarily dissolved in the jejunum (63%) and the ileum (25%). The detailed model prediction of drug dissolution in different regions of GI can provide a quantitative reference of in vivo dissolution that may provide valuable insight in developing in vitro tests for drug product optimization and quality.

Effects of Differential Food Patterns on the Pharmacokinetics of Enteric-Coated Mesalazine Tablets in the Same Cohort of Healthy Chinese Volunteers

This study aimed to simultaneously determine mesalazine (5-ASA) and its major metabolite N-Ac-5-ASA in the plasma and to evaluate the impact of different food patterns on the relative bioavailability and pharmacokinetics of a single oral dose of 5-ASA in healthy subjects. In this single-dose, open-label, 3-period, 3-treatment crossover study, the subjects received a single, oral dose of 500-mg enteric-coated mesalazine tablet together with either a low-fat or a high-fat breakfast or under fasting condition (reference). The pharmacokinetic parameters were determined by noncompartmental methods and analyzed with a linear mixed-effect model. The geometric least squares mean ratio for the area under the plasma concentration-time curve from zero to infinity of N-Ac-5-ASA was 1.05 (90% confidence interval [CI], 0.70-1.58) for high-fat/fasted condition and 1.06 (90%CI, 0.82-1.36) for low-fat/fasted condition. The least squares mean ratio of 5-ASA was 0.86 (90%CI, 0.65-1.14) for high-fat/fasted condition and 0.78 (90%CI, 0.60-1.02) for low-fat/fasted condition. All P values were >.05. The mean maximum plasma concentration and the time to reach the maximum plasma concentration of N-Ac-5-ASA were 2084 ng/mL, 8 hours; 2639 ng/mL, 11 hours, and 2409 ng/mL, 9 hours for fasted, high-fat, and low-fat, respectively. The values of 5-ASA were 1950 ng/mL, 7 hours; 2869 ng/mL, 9 hours; and 2837 ng/mL, 8 hours for fasted, high-fat, and low-fat condition. 5-ASA was well tolerated under all 3 conditions. Food delayed the absorption of 5-ASA, especially a high-fat meal. Therefore, enteric-coated mesalazine tablets should be taken before meals to avoid causing patients slow response and any effect of food on its efficacy.

Spatial and Temporal Analysis of the Stomach and Small-Intestinal Microbiota in Fasted Healthy Humans

Although the microbiota in the proximal gastrointestinal (GI) tract have been implicated in health and disease, much about these microbes remains understudied compared to those in the distal GI tract. This study characterized the microbiota across multiple proximal GI sites over time in healthy individuals. As part of a study of the pharmacokinetics of oral mesalamine administration, healthy, fasted volunteers (n = 8; 10 observation periods total) were orally intubated with a four-lumen catheter with multiple aspiration ports. Samples were taken from stomach, duodenal, and multiple jejunal sites, sampling hourly (≤7 h) to measure mesalamine (administered at t = 0), pH, and 16S rRNA gene-based composition. We observed a predominance of Firmicutes across proximal GI sites, with significant variation compared to stool. The microbiota was more similar within individuals over time than between subjects, with the fecal microbiota being unique from that of the small intestine. The stomach and duodenal microbiota displayed highest intraindividual variability compared to jejunal sites, which were more stable across time. We observed significant correlations in the duodenal microbial composition with changes in pH; linear mixed models identified positive correlations with multiple Streptococcus operational taxonomic units (OTUs) and negative correlations with multiple Prevotella and Pasteurellaceae OTUs. Few OTUs correlated with mesalamine concentration. The stomach and duodenal microbiota exhibited greater compositional dynamics than the jejunum. Short-term fluctuations in the duodenal microbiota were correlated with pH. Given the unique characteristics and dynamics of the proximal GI tract microbiota, it is important to consider these local environments in health and disease states.IMPORTANCE The gut microbiota are linked to a variety of gastrointestinal diseases, including inflammatory bowel disease. Despite this importance, microbiota dynamics in the upper gastrointestinal tract are understudied. Our article seeks to understand what factors impact microbiota dynamics in the healthy human upper gut. We found that the upper gastrointestinal tract contains consistently prevalent bacterial OTUs that dominate the overall community. Microbiota variability is highest in the stomach and duodenum and correlates with pH.

Innovation for Generic Drugs: Science and Research Under the Generic Drug User Fee Amendments of 2012

Regulatory science is science and research intended to improve decision making in a regulatory framework. Improvements in decision making can be in both accuracy (making better decisions) and in efficiency (making faster decisions). Science and research supported by the Generic Drug User Fee Amendments of 2012 (GDUFA) have focused on two innovative methodologies that work together to enable new approaches to development and review of generic drugs: quantitative models and advanced in vitro product characterization. Quantitative models faithfully represent current scientific understanding. They are tools pharmaceutical scientists and clinical pharmacologists use for making better and faster product development decisions. Advances in the in vitro product comparisons provide the measurements of product differences that are the critical input into the models. This paper outlines four areas where science and research funded by GDUFA support synergistic use of models and characterization at critical decision points during generic drug product development and review.

Case report of patient with a Cronkhite-Canada syndrome: sustained remission after treatment with corticosteroids and mesalazine

Background

Cronkhite-Canada syndrome is a rare disease of unknown etiology and the optimal treatment for this syndrome is unknown.

Case presentation

We present the case of a man who at the age of 66.0 years was diagnosed with Cronkhite-Canada syndrome (CCS). In addition to watery diarrhea, alopecia, and a complete loss of toenails and fingernails, the patient had been suffering from dysgeusia and rapid weight loss of more than 10.0 kg within a few months. The patient had recently incurred a distal radius fracture. During the initial endoscopy an extensive polyposis of the stomach and jejunum was found. The diagnosis of CCS was made and after initiation of a steroid therapy his diarrhea improved immediately. A discontinuation of the steroid therapy was not possible and mesalazine (1000 mg t.i.d.) was added to prednisolone (10.0 mg/d). This therapy led to a remission within 6.0 months with weight gain and normalization of serum albumin levels. The prednisolone dose was reduced to 7.5 mg/d. During the following year, the steroids could be further reduced and nails had regrown again. Within three years, all polyps had disappeared and the steroid therapy was finished while the dosage of mesalazine was reduced in a stepwise fashion. Four years later, the mesalazine was stopped and more than 14.0 years after the initial diagnosis the patient is still in complete remission without any treatment.

Conclusion

The optimal treatment for CCS is unknown. In our case, the initial combination therapy of corticosteroids plus mesalazine followed by a mesalazine monotherapy has led to a remarkable long-lasting remission with complete resolution of all intestinal polyps.

Drying technology strategies for colon-targeted oral delivery of biopharmaceuticals

In chronic intestinal diseases like inflammatory bowel disease, parenteral administration of biopharmaceuticals is associated with numerous disadvantages including immune reactions, infections, low patient compliance, and toxicity caused by high systemic bioavailability. One alternative that can potentially overcome these limitations is oral administration of biopharmaceuticals, where the local delivery will reduce the systemic exposure and furthermore the manufacturing costs will be lower. However, the development of oral dosage forms that deliver the biologically active form to the intestines is one of the greatest challenges for pharmaceutical technologists due to the sensitive nature of biopharmaceuticals. The present article discusses the various drug delivery technologies used to produce orally administered solid dosage forms of biopharmaceuticals with an emphasis on colon-targeted delivery. Solid oral dosage compositions containing different types of colon-targeting biopharmaceuticals are compiled followed by a review of currently applied and emerging drying technologies for biopharmaceuticals. The different drying technologies are compared in terms of their advantages, limitations, costs and their effect on product stability.

Local delivery of macromolecules to treat diseases associated with the colon

Current treatments for intestinal diseases including inflammatory bowel diseases, irritable bowel syndrome, and colonic bacterial infections are typically small molecule oral dosage forms designed for systemic delivery. The intestinal permeability hurdle to achieve systemic delivery from oral formulations of macromolecules is challenging, but this drawback can be advantageous if an intestinal region is associated with the disease. There are some promising formulation approaches to release peptides, proteins, antibodies, antisense oligonucleotides, RNA, and probiotics in the colon to enable local delivery and efficacy. We briefly review colonic physiology in relation to the main colon-associated diseases (inflammatory bowel disease, irritable bowel syndrome, infection, and colorectal cancer), along with the impact of colon physiology on dosage form design of macromolecules. We then assess formulation strategies designed to achieve colonic delivery of small molecules and concluded that they can also be applied some extent to macromolecules. We describe examples of formulation strategies in preclinical research aimed at colonic delivery of macromolecules to achieve high local concentration in the lumen, epithelial-, or sub-epithelial tissue, depending on the target, but with the benefit of reduced systemic exposure and toxicity. Finally, the industrial challenges in developing macromolecule formulations for colon-associated diseases are presented, along with a framework for selecting appropriate delivery technologies.

In Vivo Dissolution and Systemic Absorption of Immediate Release Ibuprofen in Human Gastrointestinal Tract under Fed and Fasted Conditions

In vivo drug dissolution in the gastrointestinal (GI) tract is largely unmeasured. The purpose of this clinical study was to evaluate the in vivo drug dissolution and systemic absorption of the BCS class IIa drug ibuprofen under fed and fasted conditions by direct sampling of stomach and small intestinal luminal content. Expanding current knowledge of drug dissolution in vivo will help to establish physiologically relevant in vitro models predictive of drug dissolution. A multilumen GI catheter was orally inserted into the GI tract of healthy human subjects. Subjects received a single oral dose of ibuprofen (800 mg tablet) with 250 mL of water under fasting and fed conditions. The GI catheter facilitated collection of GI fluid from the stomach, duodenum, and jejunum. Ibuprofen concentration in GI fluid supernatant and plasma was determined by LC-MS/MS. A total of 23 subjects completed the study, with 11 subjects returning for an additional study visit (a total of 34 completed study visits). The subjects were primarily white (61%) and male (65%) with an average age of 30 years. The subjects had a median [min, max] weight of 79 [52, 123] kg and body mass index of 25.7 [19.4, 37.7] kg/m². Ibuprofen plasma levels were higher under fasted conditions and remained detectable for 28 h under both conditions. The AUC_0-24 and C_max were lower in fed subjects vs fasted subjects, and T_max was delayed in fed subjects vs fasted subjects. Ibuprofen was detected immediately after ingestion in the stomach under fasting and fed conditions until 7 h after dosing. Higher levels of ibuprofen were detected in the small intestine soon after dosing in fasted subjects compared to fed. In contrast to plasma drug concentration, overall gastric concentrations remained higher under fed conditions due to increased gastric pH vs fasting condition. The gastric pH increased to near neutrality after feedingbefore decreasing to acidic levels after 7 h. Induction of the fed state reduced systemic levels but increased gastric levels of ibuprofen, which suggest that slow gastric emptying and transit dominate the effect for plasma drug concentration. The finding of high levels of ibuprofen in stomach and small intestine 7 h post dosing was unexpected. Future work is needed to better understand the role of various GI parameters, such as motility and gastric emptying, on systemic ibuprofen levels in order to improve in vitro predictive models.

Regulatory framework on bioequivalence criteria for locally acting gastrointestinal drugs: the case for oral modified release mesalamine formulations

Bioequivalence testing for locally acting gastrointestinal drugs is a challenging issue for both regulatory authorities and pharmaceutical industries. The international regulatory framework has been characterized by the lack of specific bioequivalence tests that has generated a negative impact on the market competition and drug use in clinical practice. Areas covered: This review article provides an overview of the European Union and United States regulatory frameworks on bioequivalence criteria for locally acting gastrointestinal drugs, also discussing the most prominent scientific issues and advances that has been made in this field. A focus on oral modified release mesalamine formulations will be also provided, with practical examples of the regulatory pathways followed by pharmaceutical companies to determine bioequivalence. Expert commentary: The development of a scientific rationale to demonstrate bioequivalence in this field has been complex and often associated with uncertainties related to scientific and regulatory aspects. Only in recent years, thanks to advanced knowledge in this field, the criteria for bioequivalence assessment are undergoing substantial changes. This new scenario will likely result in a significant impact on pharmaceutical companies, promoting more competition through a clearer regulatory approach, conceived for streamlining the demonstration of therapeutic equivalence for locally acting gastrointestinal drugs.