Maikel Herbrink

Variability in bioavailability of small molecular tyrosine kinase inhibitors

Small molecular tyrosine kinase inhibitors (smTKIs) are in the centre of the very quickly expanding area of personalized chemotherapy and oral applicability thereof. The number of drugs in this class is rapidly growing, with twenty current approvals by both the European Medicines Agency (EMA) and the Food and Drug Administration (FDA). The drugs are, however, generally characterized by a poor oral, and thus variable, bioavailability. This results in significant variation in plasma levels and exposure. The cause is a complex interplay of factors, including poor aqueous solubility, issued permeability, membrane transport and enzymatic metabolism. Additionally, food and drug-drug interactions can play a significant role. The issues related with an impaired bioavailability generally receive little attention. To the best of our knowledge, this article is the first to provide an overview of the factors that determine the bioavailability of the smTKIs.

Quantification of 11 therapeutic kinase inhibitors in human plasma for therapeutic drug monitoring using liquid chromatography coupled with tandem mass spectrometry

Background: A liquid chromatography/tandem mass spectrometry assay was developed to facilitate therapeutic drug monitoring (TDM) for 10 anticancer compounds (dasatinib, erlotinib, gefitinib, imatinib, lapatinib, nilotinib, pazopanib, sorafenib, sunitinib, and vemurafenib) and the active metabolite, N-desethyl-sunitinib. Methods: The TDM assay is based on reversed-phase chromatography coupled with tandem mass spectrometry in the positive ion mode using multiple reaction monitoring for analyte quantification. Stable isotopically labeled compounds were used as internal standards. The sample pretreatment consisted of protein precipitation with acetonitrile using a small plasma volume of 50 &mgr;L. The validation procedures were based on the guidelines on bioanalytical methods issued by the US Food and Drug Administration and were modified to fit the requirements of the clinical TDM environment. Results: The method was validated over a linear range of 5.00–100 ng/mL for dasatinib, sunitinib, and N-desethyl-sunitinib; 50.0–1000 ng/mL for gefitinib and lapatinib; 125–2500 ng/mL for erlotinib, imatinib, and nilotinib; and 500–10,000 ng/mL for pazopanib, sorafenib, and vemurafenib. The results of the validation study demonstrated good intra-assay and interassay accuracy (bias <6.0%) and precision (12.2%) for all analytes. Conclusions: This newly validated method met the criteria for TDM and has successfully been applied to routine TDM service for tyrosine kinase inhibitors.

Development and validation of a liquid chromatography–tandem mass spectrometry analytical method for the therapeutic drug monitoring of eight novel anticancer drugs

To support therapeutic drug monitoring of patients with cancer, a fast and accurate method for simultaneous quantification of the registered anticancer drugs afatinib, axitinib, ceritinib, crizotinib, dabrafenib, enzalutamide, regorafenib and trametinib in human plasma using liquid chromatography tandem mass spectrometry was developed and validated. Human plasma samples were collected from treated patients and stored at -20°C. Analytes and internal standards (stable isotopically labeled analytes) were extracted with acetonitrile. An equal amount of 10 mm NH4 CO3 was added to the supernatant to yield the final extract. A 2 μL aliquot of this extract was injected onto a C18 -column, gradient elution was applied and triple-quadrupole mass spectrometry in positive-ion mode was used for detection. All results were within the acceptance criteria of the latest US Food and Drug Administration guidance and European Medicines Agency guidelines on method validation, except for the carry-over of ceritinib and crizotinib. These were corrected for by the injection order of samples. Additional stability tests were carried out for axitinib and dabrafenib in relation to their reported photostability. In conclusion, the described method to simultaneously quantify the eight selected anticancer drugs in human plasma was successfully validated and applied for therapeutic drug monitoring in cancer patients treated with these drugs.

Inherent formulation issues of kinase inhibitors

The small molecular Kinase Inhibitor (smKI) drug class is very promising and rapidly expanding. All of these drugs are administered orally. The clear relationship between structure and function has led to drugs with a general low intrinsic solubility. The majority of the commercial pharmaceutical formulations of the smKIs are physical mixtures that are limited by the low drug solubility of a salt form. This class of drugs is therefore characterized by an impaired and variable bioavailability rendering them costly and their therapies suboptimal. New formulations are sparingly being reported in literature and patents. The presented data suggests that continued research into formulation design can help to develop more efficient and cost-effective smKI formulation. Moreover, it may also be of help in the future design of the formulations of new smKIs.

Improving the solubility of nilotinib through novel spray-dried solid dispersions

The tyrosine kinase inhibitor nilotinib has a very low aqueous solubility and a low and variable oral bioavailability. A pharmaceutical formulation with an improved solubility may enhance the bioavailability and reduce the variability thereof and of the pharmacokinetics. The aim of this study was to enhance the solubility of nilotinib by developing a spray dried solid dispersion. A broad selection of polymer excipients were tested for solubilizing properties. The spray drying technique was used to produce solid dispersions of nilotinib hydrochloride (NH) in matrices of the best performing polymers. Both the dissolution and physicochemical characteristics of the formulations were studied using a pH-switch dissolution model and conventional microscopic, thermal and spectrometric techniques. Of the tested spray dried solid dispersions, the ones containing the co-block polymer Soluplus® performed best in terms of in vitro dissolution properties. Further testing led to an optimized weight ratio of 1:7 (NH:Soluplus®) that improved the solubility up to 630-fold compared to crystalline NH (1.5μg/mL) in simulated intestinal fluid. This effect can be attributed to the amorphization of NH and the solubilization of the drug due to micelle formation. A spray dried solid dispersion formulation of NH with Soluplus® in a ratio of 1:7 was developed that showed a significant increase in solubility.

Thermal study of pazopanib hydrochloride

The currently marketed formulation of pazopanib hydrochloride has a poor bioavailability and pharmacokinetic profile. An alternative formulation of the drug might have an improved performance. Knowledge about the thermal behavior of the drug may be instrumental in the development process of such a formulation. The aim of this study was to thermally characterize raw bulk drug material of the multiple kinase inhibitor pazopanib hydrochloride using different analytical techniques. Solid-state characterization was carried out with Fourier transform infrared spectroscopy and X-ray diffraction. Thermal characterization was performed with thermogravimetric analysis and differential scanning calorimetry. Thermal and thermodynamic parameters were assessed using the Ozawa–Flynn–Wall, Friedman and Kissinger–Akahira–Sunose isoconversional methods.

Thermal stability study of crystalline and novel spray-dried amorphous nilotinib hydrochloride

HighlightsSpray‐dried amorphous nilotinib hydrochloride (NH) was studied.Thermal stabilities of different forms of NH were investigated.Amorphous NH has a high conformational and physical stability.Crystalline and amorphous NH have desirable thermal stability.Spray drying is a very useful technique for the production of stable amorphous NH. ABSTRACT The thermal characteristics and the thermal degradation of crystalline and amorphous nilotinib hydrochloride (NH) were studied. The spray drying technique was successfully utilized for the amorphization of NH and was evaluated by spectroscopic techniques and differential scanning calorimetry (DSC). The ethanolic spray drying process yielded amorphous NH with a glass transition temperature (Tg) of 147 °C. Thermal characterization of the amorphous phase was performed by heat capacity measurements using modulated DSC (mDSC). Thermal degradation was studied by thermogravimetric analysis (TGA). The derived thermodynamic properties of the amorphous NH indicate fragile behaviour and a low crystallization tendency. NH was found to be molecularly stable up to 193 °C. After which, the thermal degradation displayed two phases. The values of the thermal degradation parameters were estimated using the Ozawa‐Flynn‐Wall and Friedman non‐isothermal, model‐free, isoconversional methods The results indicate the two phases to be single‐step reactions. The examination of the physical stability of amorphous NH during storage and at elevated temperatures showed stability at 180 °C for at least 5 h and at 20–25 °C/60% RH for at least 6 months. During these periods, no crystallization was observed. This study is the first to report the thermal characteristics of NH. Additionally, it is also the first to describe the full thermal analysis of a spray‐dried amorphous drug. The thermal data may be used in the projection of future production processes and storage conditions of amorphous NH.

Development and validation of a high-performance liquid chromatography-tandem mass spectrometry assay for the quantification of Dexamphetamine in human plasma

HighlightsA LC–MS/MS assay is described for the quantification of dexamphetamine in plasma.The method is a new combination of simplicity, high sensitivity and full validation.The developed method is fast, easy‐to‐use and economic.Low m/z measuring problems in the clinical setting problems are briefly addressed.Applicability of the method for clinical studies was shown. ABSTRACT Dexamphetamine is registered for the treatment of attention deficit hyperactivity disorder and narcolepsy. Current research has highlighted the possible application of dexamphetamine in the treatment of cocaine addiction. To support clinical pharmacologic trials a new simple, fast, and sensitive assay for the quantification of dexamphetamine in human plasma using liquid chromatography tandem mass spectrometry (LC–MS/MS) was developed. Additionally, it is the first reported LC–MS assay with these advantages to be fully validated according to current US FDA and EMA guidelines. Human plasma samples were collected on an outpatient basis and stored at nominally −20 °C. The analyte and the internal standard (stable isotopically labeled dexamphetamine) were extracted using double liquid–liquid extraction (plasma‐organic and organic‐water) combined with snap‐freezing. The aqueous extract was filtered and 2 &mgr;L was injected on a C18‐column with isocratic elution and analyzed with triple quadrupole mass spectrometry in positive ion mode. The validated concentration range was from 2.5–250 ng/mL and the calibration model was linear. A weighting factor of 1 over the squared concentration was applied and correlation coefficients of 0.997 or better were obtained. At all concentrations the bias was within ±15% of the nominal concentrations and imprecision was ≤15%. All results were within the acceptance criteria of the latest US FDA guidance and EMA guidelines on method validation. In conclusion, the developed method to quantify dexamphetamine in human plasma was fit to support a clinical study with slow‐release dexamphetamine.

Solubility and bioavailability improvement of pazopanib hydrochloride

Graphical abstract Figure. No Caption available. Abstract The anti‐cancer drug pazopanib hydrochloride (PZH) has a very low aqueous solubility and a variable oral bioavailability. A new pharmaceutical formulation with an improved solubility may enhance the bioavailability and reduce the variability. A broad selection of polymer excipients was tested for their compatibility and solubilizing properties by conventional microscopic, thermal and spectrometric techniques. A wet milling and mixing technique was used to produce homogenous powder mixtures. The dissolution properties of the formulation were tested by a pH‐switch dissolution model. The final formulation was tested in vivo in cancer patient following a dose escalation design. Of the tested mixture formulations, the one containing the co‐block polymer Soluplus® in a 8:1 ratio with PZH performed best in terms of in vitro dissolution properties. The in vivo results indicated that 300 mg of the developed formulation yields similar exposure and a lower variability (379 &mgr;g/mL*h (36.7% CV)) than previously reported values for the standard PZH formulation (Votrient®) at the approved dose of 800 mg. Furthermore, the expected plasma‐Cthrough levels (27.2 &mgr;g/mL) exceeds the defined therapeutic efficacy threshold of 20 &mgr;g/mL.

High-Tech Drugs in Creaky Formulations

Recent literature reviews and registration documents covering novel Signal Transduction Inhibitors in the treatment of cancer paint a picture of inefficiency and variability, where formulation improvements could be valuable. In this article, we discuss apparent drug design flaws as we impose the current standard formulation practice.