Development of Mechanistic In Vitro-In Vivo Extrapolation to Support Bioequivalence Assessment of Long-Acting Injectables.

Long-acting injectable (LAI) formulations provide sustained drug release over an extended period ranging from weeks to several months to improve efficacy, safety, and compliance. Nevertheless, many challenges arise in the development and regulatory assessment of LAI drug products due to a limited understanding of the tissue response to injected particles (e.g., inflammation) impacting in vivo performance. Mechanism-based in silico methods may support the understanding of LAI-physiology interactions. The objectives of this study were as follows: (1) to use a mechanistic modeling approach to delineate the in vivo performance of DepoSubQ Provera® and formulation variants in preclinical species; (2) to predict human exposure based on the knowledge gained from the animal model. The PBPK model evaluated different elements involved in LAI administration and showed that (1) the effective in vivo particle size is potentially larger than the measured in vitro particle size, which could be due to particle aggregation at the injection site, and (2) local inflammation is a key process at the injection site that results in a transient increase in depot volume. This work highlights how a mechanistic modeling approach can identify critical physiological events and product attributes that may affect the in vivo performance of LAIs.

Balance between maternal antiviral response and placental transfer of protection in gestational SARS-CoV-2 infection.

The intricate interplay between maternal immune response to SARS-CoV-2 and the transfer of protective factors to the fetus remains unclear. By analyzing mother-neonate dyads from second and third trimester SARS-CoV-2 infections, our study shows that neutralizing antibodies (NAbs) are infrequently detected in cord blood. We uncovered that this is due to impaired IgG-NAb placental transfer in symptomatic infection and to the predominance of maternal SARS-CoV-2 NAbs of the IgA and IgM isotypes, which are prevented from crossing the placenta. Crucially, the balance between maternal antiviral response and transplacental transfer of IgG-NAbs appears to hinge on IL-6 and IL-10 produced in response to SARS-CoV-2 infection. In addition, asymptomatic maternal infection was associated with expansion of anti-SARS-CoV-2 IgM and NK cell frequency. Our findings identify a protective role for IgA/IgM-NAbs in gestational SARS-CoV-2 infection and open the possibility that the maternal immune response to SARS-CoV-2 infection might benefit the neonate in 2 ways, first by skewing maternal immune response toward immediate viral clearance, and second by endowing the neonate with protective mechanisms to curtail horizontal viral transmission in the critical postnatal period, via the priming of IgA/IgM-NAbs to be transferred by the breast milk and via NK cell expansion in the neonate.

Direct tissue-sensing reprograms TLR4+ Tfh-like cells inflammatory profile in the joints of rheumatoid arthritis patients.

CD4+ T cells mediate rheumatoid arthritis (RA) pathogenesis through both antibody-dependent and independent mechanisms. It remains unclear how synovial microenvironment impinges on CD4+ T cells pathogenic functions. Here, we identified a TLR4+ follicular helper T (Tfh) cell-like population present in the blood and expanded in synovial fluid. TLR4+ T cells possess a two-pronged pathogenic activity whereby direct TLR4+ engagement by endogenous ligands in the arthritic joint reprograms them from an IL-21 response, known to sponsor antibody production towards an IL-17 inflammatory program recognized to fuel tissue damage. Ex vivo, synovial fluid TLR4+ T cells produced IL-17, but not IL-21. Blocking TLR4 signaling with a specific inhibitor impaired IL-17 production in response to synovial fluid recognition. Mechanistically, we unveiled that T-cell HLA-DR regulates their TLR4 expression. TLR4+ T cells appear to uniquely reconcile an ability to promote systemic antibody production with a local synovial driven tissue damage program.

Physiologically relevant dissolution conditions towards improved in vitro - in vivo relationship - A case study with enteric coated pantoprazole tablets.

There are many hurdles in the development of generic formulations. In vitro biopredictive dissolution conditions together with alternative in vitro - in vivo relationship (IVIVR) approaches can be a powerful tool to support the development of such formulations. In this study, we hypothesized that the release profile of enteric coated (EC) formulations of pantoprazole in physiologically relevant bicarbonate buffer (BCB) would detect possible performance differences between test and reference formulations resulting in more accurate IVIVR results and predictability when compared to a pharmacopeial dissolution test. We correlated the in vitro performance of test and reference formulations (both in BCB and pharmacopeial phosphate buffer) with the in vivo data from a failed bioequivalence study. Test and reference formulations of EC pantoprazole tablets passed the USP dissolution criteria. However, they failed statistical similarity in vitro both in compendial and BCB. Bicarbonate buffer was additionally more discriminative while being more physiologically relevant. Having BCB as an additional test to evaluate EC products in vitro might improve the comparison of formulations. This can de-risk the development of generic EC formulations.

Mechanistic understanding of underperforming enteric coated products: Opportunities to add clinical relevance to the dissolution test.

Over the last 70 years several cases of in vivo failure of enteric coated (EC) formulations have been reported. The observed failures seem to be due to the slower than expected in vivo performance of EC products. Upon reaching the intestinal lumen, the dosage form is exposed to a bicarbonate buffered environment at much lower interfacial buffering capacity compared to those applied in compendial phosphate buffers. Hence, there is an urgent need to understand the behavior of EC products in bicarbonate buffer (BCB) and to revaluate the current dissolution methods used for such products. The current pilot study mechanistically investigated the performance of five EC products available in the Canadian market. The evaluated parameters were the buffer system (bicarbonate buffer vs. phosphate buffer), buffer capacity and medium pH. We hypothesized that the performance of EC products in BCB would be different compared with compendial phosphate buffer, giving more physiological insight, and that API properties would impact the dissolution behavior in BCB. The objective of this study was to examine the effect of the aforementioned parameters on the drug release applying physiologically relevant conditions (bicarbonate buffer at low molarities). A first step towards making the use of bicarbonate-based systems more feasible in a quality control setting is also reported. All formulations displayed a fast release in phosphate buffer and complied with the compendial performance specifications. On the other hand, they all had a much slower drug release in bicarbonate buffer and failed the USP acceptance criteria. Also, the nature of the drug (acid vs base) impacted the dissolution behavior in BCB. This pilot study indicates that compendial dissolution test for enteric coated tablets lacks physiological relevance and it needs to be reevaluated. Thus, an in vivo relevant performance method for EC products is needed.

Phytocannabinoid drug-drug interactions and their clinical implications.

Cannabis is a plant with a long history of human pharmacological use, both for recreational purposes and as a medicinal remedy. Many potential modern medical applications for cannabis have been proposed and are currently under investigation. However, its rich chemical content implies many possible physiological actions. As the use of medicinal cannabis has gained significant attention over the past few years, it is very important to understand phytocannabinoid dispositions within the human body, and especially their metabolic pathways. Even though the complex metabolism of phytocannabinoids poses many challenges, a more thorough understanding generates many opportunities, especially regarding possible drug-drug interactions (DDIs). Within this context, computer simulations are most commonly used for predicting substrates and inhibitors of metabolic enzymes. These predictions can assist to identify metabolic pathways by understanding individual CYP isoform specificities to a given molecule, which can help to predict potential enzyme inhibitions and DDIs. The reported in vivo Phase I and Phase II metabolisms of various phytocannabinoids are herein reviewed, accompanied by a parallel in silico analysis of their predicted metabolism, highlighting the clinical importance of such understanding in terms of DDIs and clinical outcomes.

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

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

Simulated, biorelevant, clinically relevant or physiologically relevant dissolution media: The hidden role of bicarbonate buffer.

In-vitro dissolution testing of pharmaceutical formulations has been used as a quality control test for many years. At early drug product development, in vivo predictive dissolution testing can be used for guidance in the rational selection of candidate formulations that best fit the desired in vivo dissolution characteristics. At present, the most widely applied dissolution media are phosphate-based buffers and, in some cases, the result of dissolution tests performed in such media have demonstrated reasonable/acceptable IVIVCs. However, the presence of phosphates in human GI luminal fluids is insignificant, which makes the use of such media poorly representative of the in vivo environment. The gastrointestinal lumen has long been shown to be buffered by bicarbonate. Hence, much interest in the development of suitable biorelevant in vitro dissolution media based on bicarbonate buffer systems has evolved. However, there are inherent difficulties associated with these buffers, such as maintaining the pH throughout the dissolution test, as CO2 tends to leave the system. Various mathematical models have been proposed to analyze bicarbonate buffers and they are discussed in this review. Approaches such as using simpler buffer systems instead of bicarbonate have been proposed as surrogate buffers to produce an equivalent buffer effect on drug dissolution on a case-by-case basis. There are many drawbacks related to simpler buffers systems including their poor in vivo predictability. Considerable discrepancies between phosphate and bicarbonate buffer dissolution results have been reported for certain dosage forms, e.g. enteric coated formulations. The role and need of bicarbonate-based buffers in quality control testing requires scientific analysis. This review also encompasses on the use of bicarbonate-based buffers as a potentially in vivo predictive dissolution medium for enteric coated dosage forms.

Are Excipients Inert? Phenytoin Pharmaceutical Investigations with New Incompatibility Insights.

PURPOSE: The U.S. Pharmacopeia defines excipients as substances other than the active pharmaceutic ingredient (API) that are added in a drug delivery system in order to aid in the manufacturing process and enhance stability, bioavailability, safety, effectiveness and delivery of the drug. The 1968 phenytoin intoxication outbreak in Brisbane, Australia, is a classic example of an API-excipient interaction. When administered with CaSO4 the absorption of phenytoin was reduced due to an interaction between the API and the excipient. When CaSO4 was replaced by lactose, the amount of drug absorbed was much higher, resulting in the observed intoxication. It was hypothesized that phenytoin was converted to a calcium salt prior to ingestion. The purpose of this study was to mechanistically investigate the interactions between excipients and phenytoin to confirm the hypothesis of the previous reports. METHODS: Titration experiments with phenytoin and calcium salt were performed. Isothermal micro calorimetry was used to determine incompatibilities between excipients, phenytoin and milk. NMR was used to characterize the compounds. Dissolution tests containing CaSO4, lactose or sorbitol as excipients were also performed. Both Canadian and United States of America commercially available capsules were tested with milk and water. RESULTS: The calorimeter results indicate that phenytoin sodium interacts with CaSO4 in aqueous media and the dissolution profile of CaSO4 containing capsules showed a reduced dissolution rate. In addition, phenytoin sodium also interacts with lactose through a Maillard reaction that can occur at body temperature. Likewise, commercial Phenytoin sodium products interacted with milk and the products containing lactose showed browning in water. CONCLUSION: In Canada and the USA, the reference product contains lactose as an excipient in the formulation, whereas the Canadian generic formulations do not contain lactose. Any clinical relevance of these difference has not been determined. A new incompatibility between phenytoin and lactose has been discovered and an incompatibility with calcium was confirmed, which may have implications in regard to excipients and food effects. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.