In Vitro and In Situ Evaluation of pH-Dependence of Atazanavir Intestinal Permeability and Interactions with Acid-Reducing Agents

The pH-dependence of efflux ratios determined with bidirectional transport assays across cellular monolayers

MDCK/Caco-2 assays serve as essential in vitro tools for evaluating membrane permeability and active transport, especially mediated by P-glycoprotein (P-gp). Despite their utility, challenges remain in quantifying active transport and using the efflux ratio (ER) to determine intrinsic values for active efflux. Such an intrinsic value for P-gp facilitated efflux necessitates knowing whether this transporter transports the neutral or ionic species of a compound. Utilising MDCK-MDR1 assays, we investigate a method for determining transporter substrate fraction preference by studying ER pH-dependence for basic, acidic and non-dissociating compounds. These results are compared with model fits based on various assumptions of transporter species preference. As an unexpected consequence of these assays, we also give evidence for an additional influx transporter at the basolateral membrane, and further extend our model to incorporate this transport. The combined influences of paracellular transport, the previously unaccounted for basolateral influx transporter, as well as potential pH effects on the transporter impedes the extraction of intrinsic values for active transport from the ER. Furthermore, we determined that using inhibitor affects the measurement of paracellular transport. While clear indications of transporter species preference remain elusive, this study enhances understanding of the MDCK system.

In situ gastric floating gel of atazanavir sulphate for sustained release: formulation, optimization and evaluation

Aim: Atazanavir sulphate belongs to BCS class II drug, its oral bioavailability is limited due to its rapid first-pass metabolism and P-gp efflux. Materials & methods: The in situ floating gel using the complexed drug was prepared by ion gelation method and optimized the formulation as per 32 full factorial design. Results: Floating lag time of optimized formulation was found to be 18 s and percentage drug release of 94.18 ± 0.18 % at the end of 16 h. The concentration of gelling polymer affects drug release and a floating lag time and vice versa. Conclusion: In situ floating gel of atazanavir sulphate was found promising to sustain drug release due to an increased gastric residence time, which leads to enhanced potential therapy.

Exploring the Use of a Kinetic pH Calculation to Correct the ACAT Model with a Single Stomach Compartment Setting: Impact of Stomach Setting on Food Effect Prediction for Basic Compounds

Advanced compartmental absorption and transit (ACAT) based computational models have become increasingly popular in the industry for predicting oral drug product performance. However, due to its complexity, some compromises have been made in practice, and the stomach is often assigned as a single compartment. Although this assignment worked generally, it may not be sufficient to reflect the complexity of the gastric environment under certain conditions. For example, this setting was found to be less accurate in estimating stomach pH and solubilization of certain drugs under food intake, which leads to a misprediction of the food effect. To overcome the above, we explored the use of a kinetic pH calculation (KpH) for the single-compartment stomach setting. Several drugs have been tested with the KpH approach and compared with the default setting of Gastroplus. In general, the Gastroplus prediction of food effect is greatly improved, suggesting this approach is effective in improving the estimation of physicochemical properties related to food effect for several basic drugs by Gastroplus.

Supersaturating lipid-based solid dispersion of atazanavir provides enhanced solubilization and supersaturation in the digestive aqueous phase

Understanding and controlling the drug solubilization in digestive environment is of great importance in the design of lipid based solid dispersion (LBSD) for oral delivery of poorly aqueous soluble drugs. In the current study we determined the extent of drug solubilization and supersaturation of supersaturating lipid based solid dispersion which is governed by formulation variables like drug payload, lipid composition, solid carrier properties and lipid to solid carrier ratio. Initially, the impact of lipid chain length and drug payload on drug solubilization in lipid preconcentrate and dispersibility were evaluated to design liquid LbF of the model antiretroviral drug, atazanavir. The temperature induced supersaturation method enhanced the drug payload in medium chain triglyceride formulation at 60 °C. Further, the selected liquid supersaturated LbF was transformed into solid state LbF by employing different solid carriers including silica (Neusilin® US2 and Aerosil® 200), clay (Montmorillonite and Bentonite) and polymer (HPMC-AS and Kollidon® CL-M). The fabricated LBSDs were evaluated for solid state characterization to identify the physical nature of drug. In vitro digestion studies were conducted using pH-stat lipolysis method to assess the supersaturation propensity in aqueous digestive phase. Results revealed that LBSDs with silica and polymer carriers showed maximum drug solubilization throughout experiment compared to liquid LbF. The ionic interaction between drug-clay particles significantly reduced the ATZ partitioning from clay based LBSDs. LBSDs with dual purpose solid carrier like HPMC-AS and Neusilin® US2 offers the potential to improve drug solubilization of ATZ for physiologically relevant time. Lastly, we conclude that evaluation of formulation variables is crucial to achieve optimal performance of supersaturating LBSD.

Nonclinical Pharmacokinetic Evaluation of Desidustat: a Novel Prolyl Hydroxylase Inhibitor for the Treatment of Anemia

BACKGROUND AND OBJECTIVES

Desidustat is a novel prolyl hydroxylase domain (PHD) inhibitor for the treatment of anemia. The objective of this study was to investigate the pharmacokinetics and drug-drug interaction properties of desidustat using in vitro and in vivo nonclinical models.

METHODS

In vitro, Caco2 cell permeability, plasma protein binding, metabolism, cytochrome P450 (CYP) inhibition, and CYP induction were examined. In vivo, pharmacokinetic studies of oral bioavailability in mice, rats, dogs and monkeys, dose linearity, tissue distribution, and excretion in rats were conducted.

RESULTS

In Caco-2 cells, the apparent permeability of desidustat was high at low pH and low at neutral pH. The oral bioavailability (%F) of desidustat was 43-100% with a median time to reach peak concentration (T_max) of about 0.25-1.3 h across species. Desidustat displayed a low mean plasma clearance (CL) of 1.3-4.1 mL/min/kg (approximately 1.8-7.4% of hepatic blood flow), and the mean steady-state volume of distribution (V_ss) was 0.2-0.4 L/kg (approximately 30-61% of the total body water). Desidustat showed a dose-dependent increase in exposures over the 15-100 mg/kg dose range. It was rapidly distributed in various tissues, with the highest tissue-to-blood ratio in the liver (1.8) and kidney (1.7). Desidustat showed high plasma protein binding and was metabolically stable in human liver microsomes, hepatocytes, and recombinant CYPs. It did not show significant inhibition of major drug-metabolizing CYP enzymes (IC₅₀ > 300 µM) or the potential to induce CYP1A2 and CYP3A4/5 (up to 100 µM) in HepG2 cells. It may have minimal potential of clinical drug-drug interaction when used in combination with iron supplements or phosphate binders. Desidustat was primarily excreted unchanged in urine (25% of the oral dose) and bile (25% of the oral dose) in rats. The mean elimination half-life of desidustat ranged from 1.0 to 5.3 h and 1.3 to 5.7 h across species after intravenous and oral administration, respectively.

CONCLUSION

Taken together, desidustat is well absorbed orally. It showed a dose-dependent increase in exposure, did not accumulate in tissue, and was eliminated via dual routes. It is metabolically stable, has minimal potential to cause clinical drug-drug interactions (DDIs), and demonstrates discriminable pharmacokinetic properties for the treatment of anemia.

Influence of Piperine and Omeprazole on The Regional Absorption of Daclatasvir from Rabbit Intestine

The study assessed the site dependent intestinal absorption of daclatasvir and investigated the effects of piperine and omeprazole on such absorption utilizing in situ rabbit intestinal perfusion technique. The intestinal absorption of daclatasvir was assessed in four segments: duodenum, jejunum, ileum, and colon. The effect of co-perfusion with omeprazole was monitored through the tested anatomical sites. The effect of piperine, a P-glycoprotein (P-gp) inhibitor on daclatasvir absorption from jejunum and ileum was tested. The results showed that daclatasvir was incompletely absorbed from the rabbit small and large intestine. The absorptive clearance per unit length (PeA/L) was site dependent and was ranked as colon > duodenum > jejunum > ileum. This rank is the opposite of the rank of P-gp intestinal content suggesting possible influence for P-gp. Co-perfusion with omeprazole increased PeA/L and this was evidenced also with reduced the L95% of daclatasvir from both small and large intestinal segments. Significant enhancement in daclatasvir absorption through jejunum and ileum was shown in presence of piperine. Daclatasvir showed site dependent intestinal absorption in a manner suggesting its affection by P-gp efflux. This effect was inhibited by piperine. Co-administration of daclatasvir with omeprazole can enhance intestinal absorption a phenomenon which requires extension to human pharmacokinetic investigation. This article is protected by copyright. All rights reserved.

Meal Effects Confound Attempts to Counteract Rabeprazole-Induced Hypochlorhydria Decreases in Atazanavir Absorption

PURPOSE

Clinically relevant pharmacokinetic interactions exist between gastric acid-reducing agents and certain weakly basic drugs that rely on acidic environments for optimal oral absorption. In this study, we examine whether the administration of betaine hydrochloride under fed conditions can enhance the absorption of atazanavir, an HIV-1 protease inhibitor, during pharmacologically-induced hypochlorhydria.

METHODS

In this randomized, single-dose, 3 period, crossover study healthy volunteers received ritonavir-boosted atazanavir (atazanavir/ritonavir 300/100 mg) alone, following pretreatment with the proton pump inhibitor rabeprazole (20 mg twice daily), and with 1500 mg of betaine HCl after rabeprazole pretreatment. Atazanavir was administered with a light meal and gastric pH was monitored using the Heidelberg Capsule.

RESULTS

Pretreatment with rabeprazole resulted in significant reductions in atazanavir C_max (p < 0.01) and AUC_0-last (p < 0.001) (71 and 70%, respectively), and modest decreases in ritonavir C_max and AUC_last (p < 0.01) (40% and 41%, respectively). The addition of betaine HCl restored 13% of ATV C_max and 12% of AUC_last lost due to rabeprazole.

CONCLUSIONS

The co-administration of rabeprazole with atazanavir resulted in significant decreases in atazanavir exposure. The addition of betaine HCl did not sufficiently mitigate the loss of ATV exposure observed during RAB-induced hypochlorhydria. Meal effects lead to a marked difference in the outcome of betaine HCl on atazanavir exposure than we previously reported for dasatanib under fasting conditions.

Role and modulation of drug transporters in HIV-1 therapy

Current treatment of human immunodeficiency virus type-1 (HIV-1) infection involves a combination of antiretroviral drugs (ARVs) that target different stages of the HIV-1 life cycle. This strategy is commonly referred to as highly active antiretroviral therapy (HAART) or combined antiretroviral therapy (cART). Membrane-associated drug transporters expressed ubiquitously in mammalian systems play a crucial role in modulating ARV disposition during HIV-1 infection. Members of the ATP-binding cassette (ABC) and solute carrier (SLC) transporter superfamilies have been shown to interact with ARVs, including those that are used as part of first-line treatment regimens. As a result, the functional expression of drug transporters can influence the distribution of ARVs at specific sites of infection. In addition, pathological factors related to HIV-1 infection and/or ARV therapy itself can alter transporter expression and activity, thus further contributing to changes in ARV disposition and the effectiveness of HAART. This review summarizes current knowledge on the role of drug transporters in regulating ARV transport in the context of HIV-1 infection.

Challenges in oral drug delivery of antiretrovirals and the innovative strategies to overcome them

Development of novel drug delivery systems (DDS) represents a promising opportunity to overcome the various bottlenecks associated with the chronic antiretroviral (ARV) therapy of the human immunodeficiency virus (HIV) infection. Oral drug delivery is the most convenient and simplest route of drug administration that involves the swallowing of a pharmaceutical compound with the intention of releasing it into the gastrointestinal tract. In oral delivery, drugs can be formulated in such a way that they are protected from digestive enzymes, acids, etc. and released in different regions of the small intestine and/or the colon. Not surprisingly, with the exception of the subcutaneous enfuvirtide, all the marketed ARVs are administered orally. However, conventional (marketed) and innovative (under investigation) oral delivery systems must overcome numerous challenges, including the acidic gastric environment, and the poor aqueous solubility and physicochemical instability of many of the approved ARVs. In addition, the mucus barrier can prevent penetration and subsequent absorption of the released drug, a phenomenon that leads to lower oral bioavailability and therapeutic concentration in plasma. Moreover, the frequent administration of the cocktail (ARVs are administered at least once a day) favors treatment interruption. To improve the oral performance of ARVs, the design and development of more efficient oral drug delivery systems are called for. The present review highlights various innovative research strategies adopted to overcome the limitations of the present treatment regimens and to enhance the efficacy of the oral ARV therapy in HIV.

Adverse drug reactions due to drug-drug interactions with proton pump inhibitors: assessment of systematic reviews with AMSTAR method

INTRODUCTION

Many systematic reviews resulted in claims on drug-drug interactions (DDIs) with proton pump inhibitors (PPIs). Such a large number begs for consensus on the clinical significance of findings.

AREAS COVERED

We critically evaluated the safety of PPI use with respect to DDIs with a meta-review of systematic reviews published between 1978 and 2015. We assessed the evidence by their reliability, repeatability, transparency, and objectivity according to the Assessment of Multiple Systematic Reviews (AMSTAR) criteria.

EXPERT OPINION

Clinicians must assess risks for each PPI for certain comorbid conditions. DDIs don't substantiate class effect for PPIs; each PPI could induce unique DDIs. Concomitant use of PPIs with thienopyridines (e.g. clopidogrel) could be justified in patients without strong affinity to cytochrome CYP2C19 and with high risk of bleeding (e.g. patients with prior upper gastrointestinal bleeding, Helicobacter pylori infection, advanced age, steroid treatment, and nonsteroidal anti-inflammatory drug use). DDIs could occur in an AIDS subpopulation treated with highly active antiretroviral therapy (HAART). DDIs exist for cancer patients undergoing targeted therapy. Hypomagnesemia could increase in the setting of advanced age and polypharmacy. Omeprazole poses high risks owing to its pharmacokinetic DDI profile. Future systematic reviews should incorporate these additional risks for better clinical guidance.