Validated HPLC-UV method for quantification of paxalisib, a pan PI3K and mTOR inhibitor in mouse plasma: Application to a pharmacokinetic study in mice.

Paxalisib is a pan-PI3K and mTOR inhibitor, currently entering into Phase II clinical trials as a potential drug to treat glioblastoma patients. We report the development and validation of a high-performance liquid chromatography (HPLC) method for the quantitation of paxalisib in mouse plasma as per the US Food and Drug Administration regulatory guidelines. From the mouse plasma, paxalisib and the internal standard (IS; filgotinib) were extracted using ethyl acetate as an extraction solvent. The chromatographic separation of paxalisib and the IS was accomplished on a Symmetry C18 (250 × 4.6 mm, 5.0 µm) column maintained at 40°C using 10 mm ammonium formate and acetonitrile in gradient conditions at a 0.8 ml/min flow-rate. The injection volume was 20 µl. The elution was monitored using a photo-diode array detector set at λmax 280 nm. Paxalisib and the IS eluted at 6.5 and 5.9 min, respectively with a total run time of 10 min. The calibration curve was linear over the range of 111-4,989 ng/ml. Inter- and intraday precision and accuracy, stability studies, dilution integrity and incurred sample reanalysis were investigated and the results met the acceptance criteria. The validated HPLC method was extended to assess the pharmacokinetic parameters of paxalisib in mice.

Validated LC-MS/MS method for the determination of copanlisib in mouse dried blood spots.

Copanlisib is a dual PI3K-δ inhibitor, used in follicular lymphoma treatment. In this research, we report a validated LC-MS/MS method for quantifying copanlisib from a mouse dried blood spot (DBS). We validated the method in line with the guidelines of the US Food and Drug Administration. The liquid-liquid extraction technique was used to extract copanlisib from the DBS discs. We used an Atlantis dC18 column and isocratic mobile phase for the chromatographic separation of copanlisib and the internal standard (idelalisib). The flow was 0.90 ml/min. Under the optimized chromatographic conditions, the retentions of copanlisib and the internal standard were 0.98 and 0.93 min, respectively. Each injection total run time was 2.50 min. The MS/MS ion transitions monitored were m/z 481.31 â†’ 128.00 and 416.10 â†’ 176.10 for copanlisib and the internal standard (IS) idelalisib, respectively. We have used a broad calibration range (1.01-4,797 ng/ml) with a determination coefficient (r2 ) of 0.997. All of the evaluated parameters met the acceptance criteria. Hematocrit did not influence the DBS copanlisib concentrations. We have used the validated method to derive the intravenous pharmacokinetic parameters by quantifying copanlisib in mouse plasma.

Validated liquid chromatography-tandem mass spectrometry method for simultaneous quantitation of bendamustine and copanlisib in mouse plasma: Application to a pharmacokinetic study in mice.

In this study, we report the development and validation of an LC-tandem mass spectrometry method for the simultaneous quantitation of bendamustine and copanlisib in mouse plasma as per the US FDA regulatory guidelines. The sample processing involves extraction of bendamustine and copanlisib along with internal standard (IS; warfarin) from 50 µL mouse plasma using a liquid-liquid extraction method. The chromatographic separation of bendamustine, copanlisib and the IS was achieved on an Atlantis dC18 column using an isocratic mobile phase (5 mM ammonium acetate:methanol, 20:80 v/v). Bendamustine, copanlisib and the IS eluted at 0.88, 1.39 and 0.74 min, respectively, with a total run time of 2.5 min. The calibration curve ranged from 3.99-2996 and 4.33-3248 ng/mL for bendamustine and copanlisib, respectively. Inter- and intra-day precision and accuracy, stability in processed samples and upon storage, dilution integrity and incurred sample reanalysis were investigated for both the analytes. The intra- and inter-day precisions were in the ranges of 2.01%-5.05% and 2.74%-6.13% and 1.98%-7.64 and 8.62%-9.04% for bendamustine and copanlisib, respectively. Stability studies showed that both analytes were stable on bench top for 6 h, in auto-sampler for 24 and at -80°C for 30 days. The validated method was successfully applied to a pharmacokinetic study in mice.

A concise review on lipidomics analysis in biological samples.

Lipids are a complex and critical heterogeneous molecular entity, playing an intricate and key role in understanding biological activities and disease processes. Lipidomics aims to quantitatively define the lipid classes, including their molecular species. The analysis of the biological tissues and fluids are challenging due to the extreme sample complexity and occurrence of the molecular species as isomers or isobars. This review documents the overview of lipidomics workflow, beginning from the approaches of sample preparation, various analytical techniques and emphasizing the state-of-the-art mass spectrometry either by shotgun or coupled with liquid chromatography. We have considered the latest ion mobility spectroscopy technologies to deal with the vast number of structural isomers, different imaging techniques. All these techniques have their pitfalls and we have discussed how to circumvent them after reviewing the power of each technique with examples..

A concise review of bioanalytical methods of small molecule immuno-oncology drugs in cancer therapy.

Immuno-oncology (IO) is an emerging option to treat cancer malignancies. In the last two years, IO has accounted for more than 90% of the new active drugs in various therapeutic indications of oncology drug development. Bioanalytical methods used for the quantitation of various IO small molecule drugs have been summarized in this review. The most commonly used are HPLC and LC-MS/MS methods. Determination of IO drugs from biological matrices involves drug extraction from the biological matrix, which is mostly achieved by simple protein precipitation, liquid-liquid extraction and solid-phase extraction. Subsequently, quantitation is usually achieved by LC-MS/MS, but HPLC-UV has also been employed. The bioanalytical methods reported for each drug are briefly discussed and tabulated for easy access. Our review indicates that LC-MS/MS is a versatile and reliable tool for the sensitive, rapid and robust quantitation of IO drugs.

Enantioselective in vitro ADME, absolute oral bioavailability, and pharmacokinetics of (-)-lumefantrine and (+)-lumefantrine in mice.

Lumefantrine (LFN) is a chiral antimalarial drug. Enantioselective in vitro attributes and absolute oral pharmacokinetics for (-)-LFN and (+)-LFN have been characterized in mice. No stereoselectivity was seen with either of the enantiomers when compared with rac-LFN in the executed in vitro studies (solubility, metabolic stability, protein binding, permeability and blood partitioning). Post intravenous or oral administration of rac-LFN, the AUC0-∞ and MRT of (+)-LFN was higher over (-)-LFN, which is reflected in higher clearance value for (-)-LFN. Following (-)-LFN intravenous administration to mice, the key PK parameters were comparable to (-)-LFN from rac-LFN; however, post intravenous administration of (+)-LFN alone to mice, the AUC0-∞ was 1.3-fold higher than (+)-LFN from rac-LFN. Similarly, post oral administration of (-)-LFN to mice, both AUC0-∞ and Cmax were 1.3-fold higher than (-)-LFN from rac-LFN. On other hand, (+)-LFN showed 1.4-fold higher AUC0-∞ and 1.7-fold higher Cmax post oral administration over (+)-LFN from rac-LFN.

DBS Assay with LC-MS/MS for the Determination of Idelalisib, A Selective PI3K-δ Inhibitor in Mice Blood and Its Application to a Pharmacokinetic Study.

Idelalisib is a selective and second-generation PI3K-δ inhibitor, approved for the treatment of non-Hodgkin lymphoma and chronic lymphocytic leukemia. In this paper, we present a fully validated dried blood spot (DBS) method for the quantitation of idelalisib from mice blood using an LC-MS/MS, which was operated under multiple reaction monitoring mode. To the punched DBS discs, acidified methanol enriched with internal standard (IS; larotrectinib) was added and extracted using tert-butyl methyl ether as an extraction solvent with sonication. Chromatographic separation of idelalisib and the IS was achieved on an Atlantis dC18 column using a mixture of 10 mM ammonium formate:acetonitrile (25:75, v/v). The flow-rate and injection volume were 0.80 mL/min and 2.0 µL, respectively. Idelalisib and the IS were eluted at ~0.98 and 0.93 min, respectively and the total run time was 2.00 min. Idelalisib and the IS were analyzed using positive ion scan mode and parent-daughter mass to charge ion (m/z) transition of 416.1→176.1 and 429.1→342.1, respectively was used for the quantitation. The calibration range was 1.01-4 797 ng/mL. No matrix effect and carry over were observed. Haematocrit did not influence DBS idelalisib concentrations. All the validation parameters met the acceptance criteria. The applicability of the validated method was shown in a mice pharmacokinetic study.

Pharmacokinetics of Darolutamide in Mouse - Assessment of the Disposition of the Diastereomers, Key Active Metabolite and Interconversion Phenomenon: Implications to Cancer Patients.

BACKGROUND: Darolutamide is recently approved for the treatment of non-metastatic castrate resistance prostate cancer. Hitherto, no stereoselective pharmacokinetic data have been published pertaining to darolutamide and its diastereomers in animals or humans. The key aims of the experiment were to examine darolutamide, S,S-darolutamide and S,R-darolutamide with respect to (a) assessment of in vitro metabolic stability and protein binding and (b) characterization of in vivo oral and intravenous pharmacokinetics in mice. METHODS: In vitro (liver microsomes stability and protein binding) and in vivo experiments (oral/intravenous dosing to mice) were carried out using darolutamide, S,S-darolutamide and S,Rdarolutamide. Besides, tissue levels of darolutamide, S,S-darolutamide and S,R-darolutamide were measured following oral and intravenous dosing. Appropriate plasma/tissue samples served to determine the pharmacokinetics of various analytes in mice. Liquid chromatography in tandem with mass spectrometry procedures enabled the delineation of the plasma pharmacokinetics, in vitro and tissue uptake data of the various analytes. RESULTS: Chiral inversion was absent in the metabolic stability study. However, darolutamide showed profound stereoselectivity (S,S-darolutamide greater than S,R-darolutamide) after either intravenous or oral dosing. S,R-darolutamide but not S,S-darolutamide showed conversion to its antipode post oral and intravenous dosing to mice. Regardless of oral or intravenous dosing, active keto darolutamide formation was evident after administration of darolutamide, S,S-darolutamide or S,R- darolutamide. Tissue data supported the observations in plasma; however, tissue exposure of darolutamide, S,Sdarolutamide and S,R-darolutamide was much lower as compared to plasma. CONCLUSION: In lieu of the human pharmacokinetic data, although the administration of diastereomeric darolutamide was justified, it is proposed to delineate the clinical pharmacokinetics of S,Rdarolutamide and S,S-darolutamide relative to darolutamide in future clinical pharmacology studies.

Validated HPLC-MS/MS method for quantitation of AMG 510, a KRAS G12C inhibitor, in mouse plasma and its application to a pharmacokinetic study in mice.

AMG 510 is the first-in-class KRASG12C inhibitor, currently in phase 2 clinical trials as an orphan drug to treat non-small cell lung cancer patients. We developed and validated a sensitive, selective, and high-throughput HPLC-MS/MS method for the quantitation of AMG 510 in mouse plasma per the regulatory guideline of the US Food and Drug and Administration. AMG 510 and the IS (MRTX-1257) were extracted from mouse plasma using tert-butyl methyl ether and chromatographed using an isocratic mobile phase (0.2% formic acid:acetonitrile; 25:75, v/v) at a flow rate of 0.65 mL/min on an Atlantis dC18 column. AMG 510 and the IS eluted at ~0.95 and 0.73 min, respectively. AMG 510 and the IS were detected by positive electrospray ionization in multiple reaction monitoring using transition pair (Q1 → Q3) m/z 561.1 → 134.1 and m/z 566.5 → 98.2, respectively. Excellent linearity was achieved in the concentration range of 1.08-5040 ng/mL (r > 0.0996). No matrix effect and carryover were observed. Intra- and inter-day accuracies and precisions were within the acceptance range. AMG 510 was demonstrated to be stable under the tested storage conditions. This novel method has been applied to a pharmacokinetic study in mice.

Validated HPLC-UV method for simultaneous quantification of phosphatidylinositol 3-kinase inhibitors, copanlisib, duvelisib and idelalisib, in rat plasma: Application to a pharmacokinetic study in rats.

Phosphatidylinositol 3-kinase (PI3K) inhibitors are a novel class of anticancer drugs that are approved to treat various malignancies. We report the development and validation of a HPLC method for the simultaneous quantitation of three PI3K inhibitors, namely copanlisib, duvelisib and idelalisib, in rat plasma as per the regulatory guidelines of the United States Food and Drug Administration. The method involves extraction of copanlisib, duvelisib and idelalisib along with an internal standard (IS; filgotinib) from rat plasma (100 µL) using a liquid-liquid extraction process. The chromatographic separation of the analytes was achieved using step-wise gradient elution on a Hypersil Gold C18 column. The UV detection wavelength was set at λmax = 280 nm. Copanlisib, duvelisib, idelalisib and the IS eluted at 7.16, 12.6, 11.9 and 9.86 min, respectively, with a total run time of 15 min. The calibration curve ranged from 50 to 5000 ng/mL for all the analytes. Inter- and intra-day precision and accuracy, stability studies, dilution integrity and incurred sample reanalysis were investigated for all three analytes, and the results met the acceptance criteria. The validated HPLC method was successfully applied to a pharmacokinetic study in rats.

A dried blood spot assay with HPLC-MS/MS for the determination of larotrectinib in mouse blood and its application to a pharmacokinetic study.

Larotrectinib is a first-generation tropomyosin kinase inhibitor, approved for the treatment of solid tumors. In this paper, we present a validated dried blood spot (DBS) method for the quantitation of larotrectinib from mouse blood using HPLC-MS/MS, which was operated under multiple reaction monitoring mode. To the DBS disc cards, acidified methanol enriched with internal standard (IS; enasidenib) was added and extracted using tert-butyl methyl ether as an extraction solvent with sonication. Chromatographic separation of larotrectinib and the IS was achieved on an Atlantis dC18 column using 10 mm ammonium formate-acetonitrile (30:70, v/v) delivered at a flow-rate of 0.80 ml/min. Under these optimized conditions, the retention times of larotrectinib and the IS were ~0.93 and 1.37 min, respectively. The total run time was 2.50 min. Larotrectinib and the IS were analyzed using positive ion scan mode and parent-daughter mass to charge ion (m/z) transitions of 429.1 → 342.1 and 474.1 → 267.1, respectively, were used for the quantitation. The calibration range was 1.06-5,080 ng/ml. No matrix effect or carryover was observed. Hematocrit did not influence DBS larotrectinib concentrations. All of the validation parameters met the acceptance criteria. The applicability of the validated method was shown in a mouse pharmacokinetic study.

Novel methodology to perform incurred sample reanalysis on dried blood spot cards: Experimental data using darolutamide and filgotinib.

Different options on performing incurred sample reanalysis (ISR) on dried blood spot (DBS) cards were investigated using drugs belonging to various therapeutic areas: (a) darolutamide (to treat prostate cancer) and (b) filgotinib (to treat rheumatoid arthritis). The proposed novel methodology included the generation of half-DBS and quarter-DBS discs after initial blood collection using the full-DBS discs. Accordingly, blood collection via DBS was performed in male BALB/c mice following intravenous and oral dosing of darolutamide; in male Sprague Dawley rats following intravenous and oral dosing of filgotinib. The ISR data generated from the full-DBS disc, half-DBS disc and quarter-DBS disc were compared for the assessment of the proposed methodology. Quantification of darolutamide and filgotinib was accomplished using liquid chromatography-electrospray ionization/tandem mass spectrometry methods. Darolutamide and filgotinib ISR samples, which were collected and prepared using full-, half- and quarter-DBS discs, met the acceptance criteria for ISR analysis. In conclusion, this is the first report showing a viable tool for the performance of ISR on DBS cards. The use of quarter- or half-DBS discs would aid in not only ISR but also in long-term storage experiments of analytes because it would avoid the need for additional blood sampling in patients.

Simultaneous determination of colchicine and febuxostat in rat plasma: Application in a rat pharmacokinetic study.

A selective, sensitive and rapid LC-MS/MS method has been developed and validated as per US Food and Drug Administration regulatory guidelines for the simultaneous quantitation of colchicine and febuxostat in rat plasma. Colchicine and febuxostat were extracted from the rat plasma using 10% tert-butyl methyl ether in ethyl acetate using colchicine-d6 as an internal standard (IS). The chromatographic separation of colchicine, febuxostat and the IS was achieved using a mobile phase comprising 5 mm ammonium formate and 0.025% formic acid in acetonitrile (20:80, v/v) in isocratic mode on an Eclipse XDB-C18 column. The injection volume and flow rate were 5.0 µl and 0.9 ml/min, respectively. Colchicine and febuxostat were detected by positive electrospray ionization in multiple reaction monitoring mode using transition pairs (Q1 → Q3) of m/z 400.10 → 358.10 and 317.05 → 261.00, respectively. The assay was linear in the ranges of 0.25-254 and 2.60-622 ng/ml for colchicine and febuxostat, respectively. The inter- and intra-day precision values were 0.58-13.0 and 1.03-4.88% for colchicine and febuxostat, respectively. No matrix or carryover effects were observed during the validation. Both analytes were stable on the bench-top, in the autosampler and in storage (freeze-thaw cycles and long-term storage at -80°C). A pharmacokinetic study in rats was performed to show the applicability of the validated method.

Validated LC-MS/MS Method for Simultaneous Quantitation of SAFit-1 and SAFit-2 in Mice Plasma: Application to a Pharmacokinetic Study.

SAFit-1 and SAFit-2 are selective FKBP51 (FK506-binding protein 51) ligands. In this paper, we present the development and validation data of an LC-MS/MS method for the simultaneous quantitation of SAFit-1 and SAFit-2 in mice plasma as per FDA regulatory guideline. SAFit-1 and SAFit-2 along with internal standard were extracted from mice plasma using liquid-liquid extraction method. Chromatographic resolution of SAFit-1, SAFit-2 and the internal standard (warfarin) was achieved on an X-Terra phenyl column using 0.2% formic acid:acetonitrile (20:80, v/v) as an eluent, which was delivered at a flow-rate of 0.9 mL/min. The MS/MS ion transitions monitored were m/z 748.4→420.4, 803.7→384.3 and 309.2 →163.2 for SAFit-1, SAFit-2 and the internal standard, respectively. The linearity range was 2.45-2446 ng/mL for both SAFit-1 and SAFit-2. The intra- and inter-day accuracy and intra- and inter-day precision were in the range of 0.90-1.07 and 2.38-10.8%, respectively for SAFit-1; 0.97-1.15 and 0.23-12.5%, respectively for SAFit-2. Both SAFit-1 and SAFit-2 were found to be stable in stability studies (up to three freeze-thaw cycles and for long-term at -80°C for 30 days) and processed (bench-top for 3 h and in in-injector for 16 h) samples. The application of the validated method was shown in a pharmacokinetic study in mice.

Enantioselective LC-ESI-MS/MS method for quantitation of (-)-lumefantrine and (+)-lumefantrine in mice plasma and application to a pharmacokinetic study.

We developed and validated a simple, sensitive, selective, and reliable LC-MS/MS-ESI method for the direct quantitation of lumefantrine (LFN) enantiomers [(-)-LFN and (+)-LFN] in mice plasma as per regulatory guideline. LFN enantiomers and carbamazepine (internal standard) were extracted from mice plasma using Strata X SPE (solid-phase extraction) cartridges. Good resolution between enantiomers was achieved on a Chiralpak IA-3 column using an isocratic mobile phase (0.1% of diethyl amine in methanol), which was delivered at a flow rate of 0.8 mL/min. Detection and quantitation were performed using multiple reaction monitoring mode following the transitions m/z 530.27 → 512.30 and 237.00 → 194.00 for LFN enantiomers and the internal standard, respectively, in the positive-ionization mode. The proposed method provided accurate and reproducible results over the linearity range of 2.39-895 ng/mL for each enantiomer. The intra- and inter-day precisions were in the range of 1.03-6.14 and 6.36-8.70 and 2.03-4.88 and 5.82-11.5 for (-)-LFN and (+)-LFN, respectively. Both (-)-LFN and (+)-LFN were found to be stable under different stability conditions. The method was successfully used to delineate stereoselective pharmacokinetics of LFN enantiomers in mice after an oral administration of rac-LFN (20 mg/kg). The pharmacokinetic results indicated that the disposition of LFN enantiomers was stereoselective in mice.

Development and Validation of an HPLC Method for Quantification of Filgotinib, a Novel JAK-1 Inhibitor in Mice Plasma: Application to a Pharmacokinetic Study.

Filgotinib is a selective JAK1 (Janus kinase) inhibitor, filed in Japan for the treatment of rheumatoid arthritis. In this paper, we present the data of development and validation of a high-performance liquid chromatography (HPLC) method for the quantitation of filgotinib in mice plasma as per the FDA regulatory guideline. The method involves the extraction of filgotinib along with internal standard (IS, tofacitinib) from mice plasma (100 µL) using ethyl acetate as an extraction solvent. The chromatographic analysis was performed using an isocratic mobile phase comprising 10 mM ammonium acetate (pH 4.5) and acetonitrile (70:30, v/v) at a flow-rate of 0.8 mL/min on a Hypersil Gold C18 column. The UV detection wavelength was set at λmax 300 nm. Filgotinib and the IS eluted at 5.56 and 4.28 min, respectively with a total run time of 10 min. The calibration curve was linear over a concentration range of 0.05 to 5.00 µg/mL (r 2+=≥0.992). The intra- and inter-day precision and accuracy results were within the acceptable limits. Results of stability studies indicated that filgotinib was stable on bench-top, in auto-sampler, up to three freeze/thaw cycles and long-term storage at -80°C. The validated HPLC method was successfully applied to a pharmacokinetic study in mice.

Discovery and optimization of novel phenyldiazepine and pyridodiazepine based Aurora kinase inhibitors.

Aurora B plays critical role in the process of chromosome condensation and chromosome orientation during the regulation of mitosis. The overexpression of Aurora B has been observed in several tumor types. As a part of our ongoing effort to develop Aurora B inhibitors, herein, we described the design, synthesis and evaluation of phenyl/pyridine diazepine analogs. The diazepane aniline pyrimidine (4a) was identified as an initial hit (Aurora B IC50 6.9 µM). Molecular modeling guided SAR optimization lead to the identification of 8-fluorobenzodiazepine (6c) with single digit nM potency (Aurora B IC50 8 nM). In the antiproliferation assay 6c showed activity across the cell lines with IC50 of 0.57, 0.42, and 0.69 µM for MCF-7, MDA-MB 231, and SkoV3 respectively. In the in vivo PK profile. 6c has shown higher bioavailability (73%) along with good exposure (AUC of 1360 ng.h/mL).

Preparation and optimization of nilotinib self-micro-emulsifying drug delivery systems to enhance oral bioavailability.

Objective: The objective of the current research was to prepare self-micro-emulsifying drug delivery systems (SMEDDS) for BCS class II drug, nilotinib to enhance its oral bioavailability.Methodology: Different types of excipients like oil, surfactant, and co-surfactant were evaluated for drug solubility. Among the screened excipients, Capryol 90, Transcutol HP, and Tween 80 were selected as oil, co-surfactant, and surfactant, respectively, to construct a ternary phase diagram to identify a homogenous mixture. Characterization performed for the prepared SMEDDS for its particle size/droplet size, emulsification time, phase separation, droplet morphology, in vitro drug release, and oral bioavailability.Results: Prepared SMEDDS showed the highest of 87% drug release in in vitro drug release experiment. SMEDDS drug release was superior over suspension formulation, which could be attributed to oil/surfactant ratios and particle size of the SMEDDS. The acquired pharmacokinetic parameters indicate that twofold increase in systemic exposure of SMEDDS compared with nilotinib suspension formulation. A similar twofold increase in relative oral bioavailability was also observed when compared SMEDDS formulation with suspension formulation. Delayed Tmax (time to reach peak plasma concentrations) was observed with SMEDDS over suspension formulation, which was evident by slow rate of absorption of nilotinib from SMEDDS.Conclusion: This research demonstrated that SMEDDS could be an effective approach to improve solubility and oral bioavailability for the BCS class II poorly soluble nilotinib.

Validated HPLC Method for Quantification of a Novel Trk Inhibitor, Larotrectinib in Mice Plasma: Application to a Pharmacokinetic Study.

Larotrectinib, is an orally active novel small molecule approved for the treatment of solid tumors in pediatrics and adult patients. It acts by inhibiting tropomyosin receptor kinase. In this paper, we report the development and validation of a high-performance liquid chromatography (HPLC) method for the quantitation of larotrectinib in mice plasma as per the FDA regulatory guideline. Plasma samples processing was accomplished through simple protein precipitation using acetonitrile enriched with internal standard (IS, enasidenib). The chromatographic analysis was performed using a gradient mobile phase comprising 10 mM ammonium acetate and acetonitrile at a flow-rate of 0.8 mL/min on an X-Terra Phenyl column. The UV detection wave length was set at λmax 262 nm. Larotrectinib and the IS eluted at 3.85 and 6.60 min, respectively with a total run time of 8.0 min. The calibration curve was linear over a concentration range of 0.20-5.00 µg/mL (r2=≥0.992). The intra- and inter-day precision and accuracy results were within the acceptable limits. Results of stability studies indicated that larotrectinib was stable on bench-top, in auto-sampler, up to three freeze/thaw cycles and long-term storage at -80°C. The validated HPLC method was successfully applied to a pharmacokinetic study in mice.

Validated LC-MS/MS method for quantitation of a selective JAK1 inhibitor, filgotinib in rat plasma, and its application to a pharmacokinetic study in rats.

Filgotinib is a selective JAK1 (Janus kinase) inhibitor, filed in Japan for the treatment of rheumatoid arthritis. In this paper, we report a validated liquid chromatography coupled with tandem mass spectrometry for the quantification of filgotinib in rat plasma using tofacitinib as an internal standard (IS) as per the Food and Drug Administration regulatory guidelines. Filgotinib and the IS were extracted from rat plasma using ethyl acetate as an extraction solvent and chromatographed using an isocratic mobile phase (0.2% formic acid:acetonitrile; 20:80, v/v) at a flow rate of 0.9 mL/min on a Gemini C18 column. Filgotinib and the IS were eluted at ~1.31 and 0.89 min, respectively. The MS/MS ion transitions monitored were m/z 426.3 → 291.3 and m/z 313.2 → 149.2 for filgotinib and the IS, respectively. The calibration range was 0.78-1924 ng/mL. No matrix effect and carryover were observed. Intra- and inter-day accuracies and precisions were within the acceptance range. Filgotinib was stable for three freeze-thaw cycles: on bench-top up to 6 h, in an autosampler up to 21 h, and at -80°C for 1 month. This novel method has been applied to a pharmacokinetic study in rats.