Population Pharmacokinetic-Pharmacodynamic Modeling and Covariate Analyses of Neutropenia and Thrombocytopenia in Patients With Solid Tumors Treated With Lurbinectedin

Lurbinectedin is a selective inhibitor of oncogenic transcription. Reversible myelosuppression is its most relevant toxicity. Pharmacokinetic-pharmacodynamic analyses were conducted to characterize the time course of absolute neutrophil count and platelet count recovery and to detect and quantify the effect of relevant covariates in patients with advanced solid tumors treated with lurbinectedin. Absolute neutrophil count, platelet count, and lurbinectedin total plasma concentration were assessed in 244 patients treated with lurbinectedin with varied dosing schedules and doses. A reference extended semimechanistic pharmacokinetic-pharmacodynamic model of myelosuppression was used. Granulocyte colony-stimulating factor (G-CSF) administration was modeled as a dichotomous covariate, and platelet transfusions were included as a bolus dose into the last compartment of the model, representing the central circulation. Final models were suitable to describe the time course of absolute neutrophil count and platelet count recovery. A lurbinectedin dose of 3.2 mg/m² every 3 weeks can be administered without primary prophylaxis with G-CSF. G-CSF followed by ≤2 dose reductions of 20%, if needed, gradually reduced grade 4 neutropenia from cycle 3 onward. BSA-based dosing reduced the incidence of grade ≥ 3 thrombocytopenia. One-week dose delays because of low absolute neutrophil count occurred in 3.5% of patients, thus supporting every-3-week administration. CYP3A inhibitors produced absolute 11.0% and 6.2% increases in grade ≥ 3 neutropenia and thrombocytopenia, respectively. Neutropenia and thrombocytopenia after lurbinectedin administration to cancer patients are noncumulative, reversible, short lasting, and clinically manageable with secondary prophylaxis of G-CSF or platelet transfusion and, if needed, dose reductions.

Development and validation of a multiplex UHPLC-MS/MS assay with stable isotopic internal standards for the monitoring of the plasma concentrations of the antiretroviral drugs bictegravir, cabotegravir, doravirine, and rilpivirine in people living with HIV

The widespread use of highly active antiretroviral treatments has dramatically changed the prognosis of people living with HIV (PLWH). However, such treatments have to be taken lifelong raising issues regarding the maintenance of both therapeutic effectiveness and long-term tolerability. Recently approved or investigational antiretroviral drugs present considerable advantages, allowing once daily oral dosage along with activity against resistant variants (eg, bictegravir and doravirine) and also parenteral intramuscular administration that facilitates treatment adherence (eg, long-acting injectable formulations such as cabotegravir and rilpivirine). Still, there remains a risk of insufficient or exaggerated circulating exposure due to absorption issues, abnormal elimination, drug-drug interactions, and others. In this context, a multiplex ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) bioassay has been developed for the monitoring of plasma levels of bictegravir, cabotegravir, doravirine, and rilpivirine in PLWH. A simple and convenient protein precipitation was performed followed by direct injection of the supernatant into the UHPLC-MS/MS system. The four analytes were eluted in less than 3 minutes using a reversed-phase chromatography method coupled with triple quadrupole mass spectrometry detection. This bioassay was fully validated following international guidelines and achieved good performances in terms of trueness (94.7%-107.5%), repeatability (2.6%-11%), and intermediate precision (3.0%-11.2%) over the clinically relevant concentration ranges (from 30 to 9000 ng/mL for bictegravir, cabotegravir, and doravirine and from 10 to 1800 ng/mL for rilpivirine). This sensitive, accurate, and rapid UHPLC-MS/MS assay is currently applied in our laboratory for routine therapeutic drug monitoring of the oral drugs bictegravir and doravirine and is also intended to be applied for the monitoring of cabotegravir/rilpivirine levels in plasma from PLWH receiving once monthly or every 2-month intramuscular injection of these long-acting antiretroviral drugs.

Development and validation of a LC-MS/MS method for the quantification of the checkpoint kinase 1 inhibitor SRA737 in human plasma

AIM

SRA737 is an orally active small-molecule inhibitor of checkpoint kinase 1 being investigated in an oncology setting. A HPLC-MS/MS method for quantifying plasma concentrations of SRA737 was validated.

METHODS & RESULTS

Sample preparation involved protein precipitation with acetonitrile following addition of 13C15N-deuterated SRA737 as internal standard. A rapid and selective method was fully validated across a range of 5-20,000 ng/ml, exhibiting good sensitivity, overall precision (expressed as coefficient of variation) ≤8.0% and accuracy 96-102%. Consistently high recovery was observed, with no matrix effect and a lower limit of quantitation of 5 ng/ml.

CONCLUSION

A novel method for analyzing SRA737 in human plasma has been validated and is now being utilized for quantification of SRA737 in a Phase I trial.

Development and validation of a high performance liquid chromatography quantification method of levo-tetrahydropalmatine and its metabolites in plasma and brain tissues: application to a pharmacokinetic study

Levo-tetrahydropalmatine (l-THP) is an alkaloid isolated from Chinese medicinal herbs of the Corydalis and Stephania genera. It has been used in China for more than 40 years mainly as an analgesic with sedative/hypnotic effects. Despite its extensive use, its metabolism has not been quantitatively studied, nor there a sensitive reliable bioanalytical method for its quantification simultaneously with its metabolites. As such, the objective of this study was to develop and validate a sensitive and selective HPLC method for simultaneous quantification of l-THP and its desmethyl metabolites l-corydalmine (l-CD) and l-corypalmine (l-CP) in rat plasma and brain tissues. Rat plasma and brain samples were processed by liquid-liquid extraction using ethyl acetate. Chromatographic separation was achieved on a reversed-phase Symmetry® C18 column (4.6 × 150 mm, 5 μm) at 25°C. The mobile phase consisted of acetonitrile-methanol-10 mm ammonium phosphate (pH 3) (10:30:60, v/v) and was used at a flow rate of 0.8 mL/min. The column eluent was monitored at excitation and emission wavelengths of 230 and 315 nm, respectively. The calibration curves were linear over the concentration range of 1-10,000 ng/mL. The intra- and interday reproducibility studies demonstrated accuracy and precision within the acceptance criteria of bioanalytical guidelines. The validated HPLC method was successfully applied to analyze samples from a pharmacokinetic study of l-THP in rats. Taken together, the developed method can be applied for bioanalysis of l-THP and its metabolites in rodents and potentially can be transferred for bioanalysis of human samples.

Gender-related pharmacokinetics and absolute bioavailability of diosbulbin B in rats determined by ultra-performance liquid chromatography-tandem mass spectrometry

ETHNOPHARMACOLOGICAL RELEVANCE

Diosbulbin B (DB) is the main constituent of furano-norditerpenes in Dioscorea bulbifera Linn., which is widely distributed in China and was usually used as a remedy for sore throat, struma and tumor. Owing to its potential antitumor activity, DB has been considered as a promising candidate for drug development.

AIM OF THE STUDY

To study the pharmacokinetic properties and excretion of DB in rats by a sensitive UPLC-MS/MS method. Absolute bioavailability and gender-related pharmacokinetic properties, as well as excretion fractions of DB in urine and feces after oral and intravenous administrations would be addressed for the first time.

MATERIALS AND METHODS

Sprague-Dawley rats were administrated orally (32mg/kg) and intravenously (0.5mg/kg) of DB, respectively. The concentrations of DB in rat plasma were determined by a sensitive and well-validated LC-MS/MS method. Main pharmacokinetic parameters including area under the plasma concentration-time curve (AUC), elimination half time (t1/2), mean residence time (MRT), apparent volume of distribution (Vd) and clearance rate (CL) were estimated using a non-compartmental pharmacokinetics data analysis software. Urine and feces of rats were collected within 48h after oral administration (32mg/kg) and detected by UPLC-MS/MS and HPLC, respectively.

RESULTS

The standard curves of DB in rat plasma and urine showed good linearity in the concentration range of 1.0-515ng/mL in the method, with acceptable selectivity, precisions, recoveries, and stability. The oral absolute bioavailability of DB in female rats was 2.0%, significantly higher than that of males (0.3%) (p<0.05). Female rats demonstrated longer t1/2 and MRT (p<0.01), bigger Vd and higher CL (p<0.05) than males after intravenous administration of DB. Bigger but no significant difference in excretion fractions of urine and feces in female rats were observed, comparing to those in males.

CONCLUSION

A simple and sensitive UPLC-MS/MS method was developed to determine the pharmacokinetic profiles of DB in rats, as well as the excretion in rat urine. Gender exerted a significant influence on the pharmacokinetics and bioavailability of DB in rats. Female rats showed significantly better absorption of DB than males after oral administration.

Simultaneous determination of evodiamine and evodine in Beagle dog plasma using liquid chromatography tandem mass spectrometry

A sensitive, rapid, and specific liquid chromatography/tandem mass spectrometry assay has been established and validated for the quantitation of evodiamine and evodine in Beagle dog plasma. Plasma samples of 0.2 ml were processed by liquid-liquid extraction with n-hexane/ethyl acetate (2:1, v/v). Chromatographic separations were done on a Symmetry C18 column (100 mm × 4.6 mm, ID, 5 μm) at 35°C with a linear gradient of methanol and 20 mM ammonium formate containing 0.2% formic acid. Evodiamine, evodine, and glibenclamide [internal standard (IS)] were ionized with an electrospray ionization source operated in positive ion mode. The MS/MS transitions were m/z 304.1 → 161.1 for evodiamine, m/z 471.2 → 425.1 for evodine, and m/z 494.1 → 369.1 for IS. Calibration curves were linear over the concentration range of 0.1-100 ng/ml for evodiamine and 0.5-500 ng/ml for evodine. The mean extraction recoveries were 88.10 ± 3.21% for evodiamine and 81.24 ± 4.07% for evodine. The intra- and inter-day precisions were less than 11.10% and 12.81%, and the accuracy was within ± 11.76% for both analytes. Evodiamine and evodine were stable during storage and analytical periods. The validated method has been successfully applied to a pharmacokinetic study of evodiamine and evodine in beagle dogs after oral administration.

Fragmentation studies of SIRT1-activating drugs and their detection in human plasma for doping control purposes

RATIONALE

The efficiency of Sirtuin1, a major target for the treatment of various metabolic disorders such as inflammation and type 2 diabetes mellitus, can be modulated via low molecular mass SIRT1 activators (e.g. resveratrol, SRT1720, and SRT2104).The administration of such compounds results in increased deacetylation of substrates including p53, FOXO1, and PGC1alpha, potentially leading to an improved physical performance. Consequently, proactive and preventive anti-doping measures are required and an assay dedicated to serum and plasma was desirable.

METHODS

Model substances of emerging SIRT1 drug candidates were obtained and synthesized and their mass spectrometric behavior following positive or negative electrospray ionization and collision-induced dissociation was elucidated using low and high resolution/high accuracy (tandem) mass spectrometry. Subsequently, a screening and confirmation procedure necessitating 100 μL of plasma was established employing liquid chromatography/tandem mass spectrometry (LC/MS/MS) based on diagnostic ion transitions recorded in multiple reaction monitoring mode. Sample preparation consisted of the addition of two deuterated internal standards (D(8)-SRT1720 and D(4)-resveratrol) to the plasma specimen and subsequent protein precipitation.

RESULTS

Characteristic product ions indicative of the core structures of the model analytes were characterized and utilized for the development of a multi-analyte LC/MS/MS detection method applicable to sports drug testing programs. The doping control assay was validated with regard to specificity, limits of detection (0.1-1 ng/mL), recoveries (90-98%), intraday and interday precisions (2-18%), and ion suppression/enhancement effects.

CONCLUSIONS

The fragmentation pathways of SRT1720 and 4 SIRT1 activator models based on a common thiazole-imidazole nucleus as well as two different complementary activators (SIRT1 activator 3 and CAY10602), comprising a quinoxaline core, were studied. The resulting information was used to establish and validate a sports drug testing methodology relevant for an efficient and timely anti-doping procedure, targeting a new class of emerging therapeutics possessing significant potential for misuse in elite and amateur sport.

Determination of PF-04928473 in human plasma using liquid chromatography with tandem mass spectrometry

A simple, rapid and sensitive liquid chromatography/tandem mass spectrometric (LC/MS/MS) analytical method was developed for quantification of Hsp90 inhibitor PF-04928473 in human plasma, following administration of its prodrug, PF-04929113. Sample processing involved protein precipitation by addition of 0.4 mL of methanol containing internal standard (PF-04972487) to 50 μL volume of plasma sample. Chromatographic separation of PF-04928473 and PF-04972487 was achieved on a Phenomenex®) Luna C18(2) (2.0 mm x 50 mm, 5 μm) column using a gradient elution method with mobile phase solvents: methanol containing 0.1% formic acid and 0.1% formic acid at a flow rate of 0.25 mL/min. Detection was performed in electrospray positive ionization mode, monitoring the ion transitions from m/z 465.1→350.1 (PF-04928473) and m/z 447.0→329.1 (PF-04972487). The retention times for PF-04928473 and PF-04972487 were 1.86 and 2.85 min, respectively. Calibration curves were generated in the range of 2-2000 ng/mL. The accuracy and precision ranged from 94.1 to 99.0% and 86.7 to 97.6%, respectively, which were calculated using quality control samples of three different concentrations analyzed in quintuplicate on four different days.

LC−MS/MS Screen for Penitrem A and Roquefortine C in Serum and Urine Samples

A rapid LC-MS/MS method, using a triple quadrupole/linear ion trap mass spectrometer, was developed for determination of penitrem A and roquefortine C in serum and urine samples. Penitrem A and roquefortine C were extracted from samples with methylene chloride. The extracts were injected onto a liquid chromatograph coupled with a hybrid triple quadrupole/linear ion trap mass spectrometer. Seven replicate fortifications of serum at 0.001 microg/g (1 ppb) each of penitrem A and roquefortine C gave average recoveries of 90% with 10% CV (relative standard deviation) and 97% with 3% CV, respectively. Seven replicate fortifications of urine at 0.001 microg/g (1 ppb) each of penitrem A and roquefortine C gave average recoveries of 98% with 12% CV and 100% with 6% CV, respectively. This is the first report of a positive mass spectrometric identification and quantitation of both compounds in urine and serum samples from dog intoxication cases.

Pharmacokinetics of Guanfu Base I, an Active Metabolite of Guanfu Base A, in Rats

A liquid chromatographic-mass spectrometric (LC-MS) method was developed and validated for determination of guanfu base I (GFI), and the pharmacokinetics of GFI in Sprague-Dawley rats was examined. The method was linear in the 0.05-20 mug/ml concentration range (r=0.9994). The recovery of guanfu base I was more than 80%. The intraday and interday precision, expressed as the relative standard deviation (RSD), was generally good (<15%). After i.v. dosing, plasma GFI concentration declined in a bi-phasic manner with a terminal elimination half-life of 2.49 h. The total plasma clearance values was 1.46 l/h/kg. After oral dosing, the plasma GFI concentration reached a maximum within 0.5 h. The absolute bioavailability of GFI was 71.31%.