Generics in transplantation medicine: Randomized comparison of innovator and substitution products containing mycophenolate mofetil
.

OBJECTIVE: Mycophenolate mofetil (MMF) is widely used as an immunosuppressant for the prophylaxis of acute organ rejection in recipients of solid organ transplants. MATERIALS AND METHODS: We have compared, in healthy subjects, the pharmacokinetics of mycophenolic acid when MMF was administered in the form of the innovator product CellCept (F. Hoffmann-La Roche Ltd.) or one of three commercially available generics, Renodapt (Biocon Ltd.), Mycept (Panacea Biotec), or Cellmune (Cipla Ltd.). The study was powered to detect a 20% difference in mean formulation performance measures, but not to formally evaluate bioequivalence. Geometric mean ratios of maximum concentrations (Cmax) and areas under plasma concentration-time curves were calculated. RESULTS: Comparing generics against each other, the differences in point estimates of the geometric mean ratios of Cmax of two of the comparisons were either borderline within (Renodapt/Cellmune) or clearly outside (Mycept/Cellmune) a region of 80 - 125% around the reference mean, indicating that bioequivalence between these generics may be difficult to show. CONCLUSION: Physicians in the field of transplantation should be aware of the potential risk of altering the therapeutic outcome when switching from one preparation of MMF to another. ClinicalTrials.gov identifier: NCT02981290.

Physiologically based absorption modelling to predict the impact of drug properties on pharmacokinetics of bitopertin.

Bitopertin (RG1678) is a glycine reuptake inhibitor in phase 3 trials for treatment of schizophrenia. Its clinical oral pharmacokinetics is sensitive to changes in drug substance particle size and dosage form. Physiologically based pharmacokinetic (PBPK) absorption model simulations of the impact of changes in particle size and dosage form (either capsules, tablets, or an aqueous suspension) on oral pharmacokinetics was verified by comparison to measured plasma concentrations. Then, a model parameter sensitivity analysis was applied to set limits on the particle sizes included in tablets for the market. The model was also used to explore the in vitro to in vivo correlation. Simulated changes in oral pharmacokinetics caused by differences in particle size and dosage form were confirmed in two separate relative bioavailability studies. Model parameter sensitivity analyses predicted that AUCinf was hardly reduced as long as particle diameter (D50) remained smaller than 30 µm, and >20% reduced Cmax is anticipated only when particle diameter exceeds 15 µm. An exploration of the sensitivity to the presence of larger particles within a polydisperse distribution showed that simulated Cmax is again more affected than AUC but is less than 20% reduced as long as D50 is less than 8 µm and D90 is smaller than 56 µm. PBPK absorption modelling can contribute to a quality by design (QbD) approach for clinical formulation development and support the setting of biorelevant specifications for release of the product.

Miniaturized screening of polymers for amorphous drug stabilization (SPADS): rapid assessment of solid dispersion systems.

PURPOSE: Development of a novel, rapid, miniaturized approach to identify amorphous solid dispersions with maximum supersaturation and solid state stability. METHOD: Three different miniaturized assays are combined in a 2-step decision process to assess the supersaturation potential and drug-polymer miscibility and stability of amorphous compositions. Step 1: SPADS dissolution assay. Drug dissolution is determined in 96-well plates to detect systems that generate and maintain supersaturation. Promising combinations graduate to step 2. Step 2: SPADS interaction and SPADS imaging assays. FTIR microspectroscopy is used to study intermolecular interactions. Atomic force microscopy is applied to analyze molecular homogeneity and stability. Based on the screening results, selected drug-polymer combinations were also prepared by spray-drying and characterized by classical dissolution tests and a 6-month physical stability study. RESULTS: From the 7 different polymers and 4 drug loads tested, EUDRAGIT E PO at a drug load of 20% performed best for the model drug CETP(2). The classical dissolution and stability tests confirmed the results from the miniaturized assays. CONCLUSION: The results demonstrate that the SPADS approach is a useful de-risking tool allowing the rapid, rational, time- and cost-effective identification of polymers and drug loads with appropriate dual function in supersaturation performance and amorphous drug stabilization.

Improved human bioavailability of vemurafenib, a practically insoluble drug, using an amorphous polymer-stabilized solid dispersion prepared by a solvent-controlled coprecipitation process.

The present work deals with improving the solubility of vemurafenib, a practically insoluble drug, by converting it into an amorphous-solid dispersion using a solvent-controlled precipitation process. The dispersion containing vemurafenib and hypromellose acetate succinate (HPMCAS), an enteric polymer, is termed microprecipitated bulk powder (MBP), in which the drug is uniformly dispersed within the polymeric substrate. HPMCAS was found to be the most suitable polymer for vemurafenib MBP, among a series of enteric polymers based on superior physical stability and drug-release characteristics of the MBP. The MBP provided a greater rate and extent of dissolution than crystalline drug, reaching an apparent drug concentration of 28-35 µg/mL, almost 30-fold higher than solubility of crystalline drug at 1 µg/mL. The supersaturation was also maintained for more than 4 h. Upon exposure to high temperature and humidity, the MBP was destabilized, resulting in crystallization and lower dissolution rate. The control of moisture and temperature is essential to maintain the stability of the MBP. In a relative human bioavailability study, vemurafenib MBP provided a four- to fivefold increase in exposure compared with crystalline drug. Improving solubility with an amorphous-solid dispersion is a viable strategy for the development of practically insoluble compounds.

Selection of the most suitable dissolution method for an extended release formulation based on IVIVC level A obtained on cynomolgus monkey.

OBJECTIVE: The purpose of this study is primarily to identify the most suitable in vitro dissolution method(s) for their ability to predict the in vivo performance of extended release prototype tablet formulations designed for a new chemical entity, Biopharmaceutic Classification System class II drug, weak base, based on the data collected in cynomolgus monkey. MATERIALS AND METHODS: Different types of buffer at different pH were selected as dissolution medium resulting in a broad variety of release patterns (slow to fast). The in vivo and in vitro data were put in relation. RESULTS: As a consequence of the discrimination between both tested formulations, the in vitro-in vivo correlation (IVIVC) qualities and shapes changed significantly. The obtained level A showed that the simple HCl medium was superior to biorelevant media and media containing surfactant when investigating IVIVCs in cynomolgus monkey. In addition, the results of dissolution in HCl suggested rather a diffusion mechanism of the extended release matrix formulation as the main factor of the release. CONCLUSION: Adjusting dissolution testing conditions to match the behavior of the formulations in vitro with that in vivo by taking into account the properties of the drug and the formulation is a straightforward and useful approach in identifying a predictive method in the development of the IVIVC. These investigations will definitely help by derisking of new formulations as well as by rating changes in existing formulations with regard to their impact on bioavailability before entry into human.

Small Volume Dissolution Testing as a Powerful Method during Pharmaceutical Development.

Standard compendia dissolution apparatus are the first choice for development of new dissolution methods. Nevertheless, limitations coming from the amount of material available, analytical sensitivity, lack of discrimination or biorelevance may warrant the use of non compendial methods. In this regard, the use of small volume dissolution methods offers strong advantages. The present study aims primarily to evaluate the dissolution performance of various drug products having different release mechanisms, using commercially available small volume USP2 dissolution equipment. The present series of tests indicate that the small volume dissolution is a useful tool for the characterization of immediate release drug product. Depending on the release mechanism, different speed factors are proposed to mimic common one liter vessel performance. In addition, by increasing the discriminating power of the dissolution method, it potentially improves know how about formulations and on typical events which are evaluated during pharmaceutical development such as ageing or scale-up. In this regard, small volume dissolution is a method of choice in case of screening for critical quality attributes of rapidly dissolving tablets, where it is often difficult to detect differences using standard working conditions.