Final results of urelumab, an anti-CD137 agonist monoclonal antibody, in combination with cetuximab or nivolumab in patients with advanced solid tumors.

BACKGROUND: Resistance to immune checkpoint inhibitors and targeted treatments for cancer is common; thus, novel immunotherapy agents are needed. Urelumab is a monoclonal antibody agonist that binds to CD137 receptors expressed on T cells. Here, we report two studies that evaluated urelumab in combination with cetuximab or nivolumab in patients with select, advanced solid tumors. METHODS: CA186-018: Patients with metastatic colorectal cancer or metastatic squamous cell carcinoma of the head and neck (SCCHN) were treated in a dose-evaluation phase with urelumab 0.1 mg/kg (urelumab-0.1) every 3 weeks (Q3W)+cetuximab 250 mg/m2 (cetuximab-250) weekly; and in a dose-expansion phase with urelumab 8 mg flat dose (urelumab-8) Q3W+cetuximab-250 weekly. CA186-107: The dose-escalation phase included patients with previously treated advanced solid tumors (or treated or treatment-naive melanoma); patients received urelumab 3 mg flat dose (urelumab-3) or urelumab-8 every 4 weeks+nivolumab 3 mg/kg (nivolumab-3) or 240 mg (nivolumab-240) every 2 weeks. In the expansion phase, patients with melanoma, non-small cell lung cancer, or SCCHN were treated with urelumab-8+nivolumab-240. Primary endpoints were safety and tolerability, and the secondary endpoint included efficacy assessments. RESULTS: CA186-018: 66 patients received study treatment. The most frequent treatment-related adverse events (TRAEs) were fatigue (75%; n=3) with urelumab-0.1+cetuximab-250 and dermatitis (45%; n=28) with urelumab-8+cetuximab-250. Three patients (5%) discontinued due to TRAE(s) (with urelumab-8+cetuximab-250). One patient with SCCHN had a partial response (objective response rate (ORR) 5%, with urelumab-8+cetuximab-250).CA186-107: 134 patients received study treatment. Fatigue was the most common TRAE (32%; n=2 with urelumab-3+nivolumab-3; n=1 with urelumab-8+nivolumab-3; n=40 with urelumab-8+nivolumab-240). Nine patients (7%) discontinued due to TRAE(s) (n=1 with urelumab-3+nivolumab-3; n=8 with urelumab-8+nivolumab-240). Patients with melanoma naive to anti-PD-1 therapy exhibited the highest ORR (49%; n=21 with urelumab-8+nivolumab-240). Intratumoral gene expression in immune-related pathways (CD3, CD8, CXCL9, GZMB) increased on treatment with urelumab+nivolumab. CONCLUSIONS: Although the addition of urelumab at these doses was tolerable, preliminary response rates did not indicate an evident additive benefit. Nevertheless, the positive pharmacodynamics effects observed with urelumab and the high response rate in treatment-naive patients with melanoma warrant further investigation of other anti-CD137 agonist agents for treatment of cancer. TRIAL REGISTRATION NUMBERS: NCT02110082; NCT02253992.

Model-Informed Clinical Pharmacology Profile of a Novel Fixed-Dose Combination of Nivolumab and Relatlimab in Adult and Adolescent Patients with Solid Tumors.

PURPOSE: Progression-free survival (PFS) was significantly improved with nivolumab 480 mg plus relatlimab 160 mg fixed-dose combination (FDC) every 4 weeks (Q4W) vs nivolumab alone in patients with previously untreated advanced melanoma in RELATIVITY-047. Additionally, RELATIVITY-020 (Part D) demonstrated a manageable safety profile and potential for durable response with nivolumab plus relatlimab in previously treated patients. Here we evaluate the clinical pharmacology profile (CPP) of nivolumab plus relatlimab to support the approved regimen for adult and adolescent patients with advanced melanoma and its continued clinical development in solid tumors. PATIENTS AND METHODS: The pharmacokinetics (PK) and immunogenicity of relatlimab and nivolumab were assessed using data from RELATIVITY-047 and RELATIVITY-020. Patients with advanced solid tumors received relatlimab alone or nivolumab plus relatlimab as single-agent vials (SAV) or FDC. PK was characterized using a population PK (popPK) model. RESULTS: Relatlimab demonstrated nonlinear and time-varying PK. Nonlinearity in relatlimab PK represented ~31% of total CL of relatlimab 160 mg Q4W. Relatlimab PK was dose proportional at doses ≥160 mg Q4W. Geometric mean exposures were similar for SAV and FDC cohorts receiving equivalent dosing regimens. No dose adjustment was required for covariates. Incidence of relatlimab antidrug antibodies was <6% for nivolumab plus relatlimab and had no clinically meaningful impact. There was no PK-related drug interaction of nivolumab plus relatlimab. CONCLUSION: The CPP of relatlimab alone or in combination with nivolumab supports the approved dosing in advanced melanoma and the continued evaluation of nivolumab and relatlimab across other solid tumors.

Nivolumab and Relatlimab in Patients With Advanced Melanoma That Had Progressed on Anti-Programmed Death-1/Programmed Death Ligand 1 Therapy: Results From the Phase I/IIa RELATIVITY-020 Trial.

PURPOSE: Nivolumab and relatlimab activity in advanced melanoma with prior progression on anti-programmed death-1/programmed death ligand 1 (PD-(L)1)-containing regimens is under investigation. RELATIVITY-047 demonstrated significantly improved progression-free survival (PFS) for nivolumab and relatlimab over nivolumab in previously untreated advanced melanoma. METHODS: The phase I/IIa, open-label RELATIVITY-020 trial part D assessed efficacy and safety of nivolumab and relatlimab in advanced melanoma with progression during, or within 3 months of, 1 (D1) or ≥ 1 (D2) anti-PD-(L)1-containing regimens. Safety was a primary end point. Objective response rate (coprimary end point) and PFS by blinded independent central review (BICR) were assessed. RESULTS: Five hundred eighteen patients (D1 = 354; D2 = 164) received nivolumab and relatlimab. Among evaluable patients, the objective response rate by BICR was 12.0% (95% CI, 8.8 to 15.8) in D1 (n = 351) and 9.2% (95% CI, 5.2 to 14.7) in D2 (n = 163). Responses appeared to be enriched among patients with tumors expressing programmed death ligand 1 or lymphocyte activation gene 3; however, responses were observed regardless of programmed death ligand 1 and lymphocyte activation gene 3 expression (1%). The median duration of response was not reached (95% CI, 12.9 to not reached) in D1 and 12.8 months (95% CI, 6.9 to 12.9) in D2. The median PFS by BICR was 2.1 months (95% CI, 1.9 to 3.5) in D1 and 3.2 months (95% CI, 1.9 to 3.6) in D2; the 6-month PFS rate was 29.1% (95% CI, 24.2 to 34.1) and 27.7% (95% CI, 20.5 to 35.4), respectively. The grade 3-4 treatment-related adverse event incidence was 15.0% in D1 and 12.8% in D2. One case of grade 3 myocarditis and no treatment-related deaths occurred across part D. CONCLUSION: Nivolumab and relatlimab had a manageable safety profile and demonstrated durable clinical activity in a proportion of patients with heavily pretreated advanced melanoma with prior progression on anti-PD-(L)1-containing regimens.[Media: see text].

Nivolumab exposure-response analysis for adjuvant treatment of melanoma supporting a change in posology.

Nivolumab monotherapy is approved as adjuvant treatment for melanoma based on results from the pivotal CheckMate 238 trial. We present a model-based, benefit-risk assessment of nivolumab in adjuvant melanoma supporting a posology change from a weight-based to a less frequent, flat-dosing regimen. The exposure-response (E-R) relationship for efficacy was evaluated using recurrence-free survival (RFS) and distant metastasis-free survival (DMFS) end points from the CheckMate 238 trial. The E-R for safety was evaluated using data from 14 studies across a broad range of doses in several tumor types using grade 3+ adverse event (AE) and grade 2+ immune-mediated AE (IMAE) end points. Nivolumab trough exposures were not significant predictors of RFS or DMFS. Covariates significantly associated with increased risk of disease recurrence or death were programmed death ligand 1 (PD-L1; less than 5% cutoff), lower baseline lactate dehydrogenase, and higher age. Covariates associated with increased risk of distant metastasis or death were PD-L1 (less than 5% cutoff) and higher age. Higher nivolumab maximum concentration after first dose (Cmax1) was significantly associated with grade 2+ IMAEs, but not grade 3+ AEs. The risk of grade 3+ AEs was significantly lower in adjuvant versus advanced melanoma. Eastern Cooperative Oncology Group Performance Status higher than zero was associated with higher incidences of grade 2+ IMAEs and grade 3+ AEs. Female patients had significantly higher incidences of grade 2+ IMAEs than male patients. Nivolumab monotherapy in adjuvant melanoma demonstrated a relatively flat E-R relationship over the range of exposures produced by 3 mg/kg every 2 weeks and predicted a comparable benefit-risk profile to flat-dosing regimens.

Pharmacokinetics and Clinical Pharmacology of Monoclonal Antibodies in Pediatric Patients.

Monoclonal antibodies (mAbs) and their derivatives are increasingly used in pediatric pharmacotherapy, and the number of antibody-based drug products with approved pediatric indications is continuously growing. In most instances, pediatric use is being pursued after the efficacy and safety of novel antibody medications have been established in adult indications. The pediatric extrapolation exercise that is frequently used in this context to bridge efficacy and safety from adults to children is oftentimes challenged through uncertainties and knowledge gaps in how to reliably extrapolate pharmacokinetics and clinical pharmacology of mAbs to different pediatric age groups, and how to derive age-appropriate dosing regimens that strike a balance between precision dosing and practicability. The article highlights some of the pharmacokinetic and clinical pharmacology challenges with regard to therapeutic use of mAbs and antibody derivatives in children, including immunogenicity events. Although considering body size-based differences in drug disposition can account for many of the perceived and actual differences in the distribution and elimination of antibody-based therapeutics between children and adults, increasing evidence suggests potential or actual age-associated differences beyond size differences, especially for young pediatric patients such as newborns and infants. To overcome age-associated differences in antibody disposition, various different dosing approaches have been applied to ensure safe and efficacious antibody exposure for pediatric populations of different ages. The development of such dosing regimens and the associated pathway to pediatric indication approval is illustrated in more detail for two antibody-based biologics, the fusion protein abatacept and the mAb tocilizumab.

Urelumab alone or in combination with rituximab in patients with relapsed or refractory B-cell lymphoma.

Urelumab, a fully human, non-ligand binding, CD137 agonist IgG4 monoclonal antibody, enhances T-cell and natural killer-cell antitumor activity in preclinical models, and may enhance cytotoxic activity of rituximab. Here we report results in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), and other B-cell lymphomas, in phase 1 studies evaluating urelumab alone (NCT01471210) or combined with rituximab (NCT01775631). Sixty patients received urelumab (0.3 mg/kg IV Q3W, 8 mg IV Q3W, or 8 mg IV Q6W); 46 received urelumab (0.1 mg/kg, 0.3 mg/kg, or 8 mg IV Q3W) plus rituximab 375 mg/m2 IV QW. The maximum tolerated dose (MTD) of urelumab was determined to be 0.1 mg/kg or 8 mg Q3W after a single event of potential drug-induced liver injury occurred with urelumab 0.3 mg/kg. Treatment-related AEs were reported in 52% (urelumab: grade 3/4, 15%) and 72% (urelumab + rituximab: grade 3/4, 28%); three led to discontinuation (grade 3 increased AST, grade 4 acute hepatitis [urelumab]; one death from sepsis syndrome [urelumab plus rituximab]). Objective response rates/disease control rates were 6%/19% (DLBCL, n = 31), 12%/35% (FL, n = 17), and 17%/42% (other B-cell lymphomas, n = 12) with urelumab and 10%/24% (DLBCL, n = 29) and 35%/71% (FL, n = 17) with urelumab plus rituximab. Durable remissions in heavily pretreated patients were achieved; however, many were observed at doses exceeding the MTD. These data show that urelumab alone or in combination with rituximab demonstrated manageable safety in B-cell lymphoma, but the combination did not enhance clinical activity relative to rituximab alone or other current standard of care.

Linking Tumor Growth Dynamics to Survival in Ipilimumab-Treated Patients With Advanced Melanoma Using Mixture Tumor Growth Dynamic Modeling.

Early tumor assessments have been widely used to predict overall survival (OS), with potential application to dose selection and early go/no-go decisions. Most published tumor dynamic models assume a uniform pattern of tumor growth dynamics (TGDs). We developed a mixture TGD model to characterize different patterns of longitudinal tumor sizes. Data from 688 patients with advanced melanoma who received ipilimumab 3 or 10 mg/kg every 3 weeks in a phase III study (NCT01515189) were used in a TGD-OS analysis. The mixture model described TGD profiles using three subpopulations (no-growth, intermediate, and fast). The TGD model showed a positive exposure/dose-response (i.e., a higher proportion of patients in no/intermediate growth subpopulations and a lower tumor growth rate with ipilimumab 10 mg/kg relative to the 3 mg/kg dose). Finally, the mixture TGD model-based measures of tumor response provided better predictions of OS compared with the nonmixture model.

Evaluation of covariate effects on pharmacokinetics of monoclonal antibodies in oncology.

AIMS: The development of monoclonal antibodies (mAbs) requires an understanding of the interindividual variability (IIV) in pharmacokinetics (PK) at the population level facilitated by population PK (PopPK) modelling. However, there is no clear rationale for selecting which covariates to screen during PopPK model development. Here, we compare the effect of covariates on PK parameters for mAbs in oncology and identify the most commonly used covariates affecting PK parameters. METHODS: All 25 mAbs approved for therapeutic use in oncology until December 2017 by the Food and Drug Administration and the European Medicines Agency were selected for study. Literature searches revealed 23 available PopPK models for these mAbs. To understand the magnitude and types of covariate effect on PK parameters, all covariates included in the final PopPK model for each mAb were summarized. RESULTS: The most commonly identified covariates were baseline body weight (BW; 17 mAbs), baseline serum albumin (8 mAbs), and sex (7 mAbs) on clearance; and BW (16 mAbs) and sex (12 mAbs) on central volume of distribution. A reduced PopPK model was developed for nivolumab and ipilimumab using these covariates, and the percentage of explained IIV from the reduced model (20.3% and 16.8%, respectively) was compared with that from the full model (24.5% and 27.9%, respectively). CONCLUSIONS: This analysis provides a uniform platform for selecting covariates and suggests that the effect of BW, albumin and sex should be included during the development of PopPK models for mAbs in oncology. The reduced model was able to explain IIV to a similar extent as the full model.

Reporting, Visualization, and Modeling of Immunogenicity Data to Assess Its Impact on Pharmacokinetics, Efficacy, and Safety of Monoclonal Antibodies.

The rapidly increasing number of therapeutic biologics in development has led to a growing recognition of the need for improvements in immunogenicity assessment. Published data are often inadequate to assess the impact of an antidrug antibody (ADA) on pharmacokinetics, safety, and efficacy, and enable a fully informed decision about patient management in the event of ADA development. The recent introduction of detailed regulatory guidance for industry should help address many past inadequacies in immunogenicity assessment. Nonetheless, careful analysis of gathered data and clear reporting of results are critical to a full understanding of the clinical relevance of ADAs, but have not been widely considered in published literature to date. Here, we review visualization and modeling of immunogenicity data. We present several relatively simple visualization techniques that can provide preliminary information about the kinetics and magnitude of ADA responses, and their impact on pharmacokinetics and clinical endpoints for a given therapeutic protein. We focus on individual sample- and patient-level data, which can be used to build a picture of any trends, thereby guiding analysis of the overall study population. We also discuss methods for modeling ADA data to investigate the impact of immunogenicity on pharmacokinetics, efficacy, and safety.

Translational pharmacokinetic-pharmacodynamic analysis in the pharmaceutical industry: an IQ Consortium PK-PD Discussion Group perspective.

With inadequate efficacy being the primary cause for the attrition of drug candidates in clinical development, the need to better predict clinical efficacy earlier in the drug development process has increased in importance in the pharmaceutical industry. Here, we review current applications of translational pharmacokinetic-pharmacodynamic (PK-PD) modeling of preclinical data in the pharmaceutical industry, including best practices. Preclinical translational PK-PD modeling has been used in many therapeutic areas and has been impactful to drug development. The role of preclinical translational PK-PD modeling in drug discovery and development will continue to evolve and broaden, given that its broad implementation in the pharmaceutical industry is relatively recent and many opportunities still exist for its further application.

Results from an Integrated Safety Analysis of Urelumab, an Agonist Anti-CD137 Monoclonal Antibody.

Purpose: Urelumab is an agonist antibody to CD137 with potential application as an immuno-oncology therapeutic. Data were analyzed to assess safety, tolerability, and pharmacodynamic activity of urelumab, including the dose selected for ongoing development in patients with advanced solid tumors and lymphoma.Experimental Design: A total of 346 patients with advanced cancers who had progressed after standard treatment received at least one dose of urelumab in one of three dose-escalation, monotherapy studies. Urelumab was administered at doses ranging from 0.1 to 15 mg/kg. Safety analyses included treatment-related and serious adverse events (AEs), as well as treatment-related AEs leading to discontinuation and death, with a focus on liver function test abnormalities and hepatic AEs.Results: Urelumab doses between 1 and 15 mg/kg given every 3 weeks resulted in a higher frequency of treatment-related AEs than 0.1 or 0.3 mg/kg every 3 weeks. Dose was the single most important factor contributing to transaminitis development, which was more frequent and severe at doses ≥1 mg/kg. At the MTD of 0.1 mg/kg every 3 weeks, urelumab was relatively well tolerated, with fatigue (16%) and nausea (13%) being the most common treatment-related AEs, and was associated with immunologic and pharmacodynamic activity demonstrated by the induction of IFN-inducible genes and cytokines.Conclusions: Integrated evaluation of urelumab safety data showed significant transaminitis was strongly associated with doses of ≥1 mg/kg. However, urelumab 0.1 mg/kg every 3 weeks was demonstrated to be safe, with pharmacodynamic activity supporting continued clinical evaluation of this dose as monotherapy and in combination with other immuno-oncology agents. Clin Cancer Res; 23(8); 1929-36. ©2016 AACR.

Preclinical evaluation of SMM-189, a cannabinoid receptor 2-specific inverse agonist.

Cannabinoid receptor 2 agonists and inverse agonists are emerging as new therapeutic options for a spectrum of autoimmune-related disease. Of particular interest, is the ability of CB2 ligands to regulate microglia function in neurodegenerative diseases and traumatic brain injury. We have previously reported the receptor affinity of 3',5'-dichloro-2,6-dihydroxy-biphenyl-4-yl)-phenyl-methanone (SMM-189) and the characterization of the beneficial effects of SMM-189 in the mouse model of mild traumatic brain injury. Herein, we report the further characterization of SMM-189 as a potent and selective CB2 inverse agonist, which acts as a noncompetitive inhibitor of CP 55,940. The ability of SMM-189 to regulate microglial activation, in terms of chemokine expression and cell morphology, has been determined. Finally, we have determined that SMM-189 possesses acceptable biopharmaceutical properties indicating that the triaryl class of CB2 inverse agonists are viable compounds for continued preclinical development for the treatment of neurodegenerative disorders and traumatic brain injury.

Preclinical pharmacokinetic/pharmacodynamic modeling and simulation in the pharmaceutical industry: an IQ consortium survey examining the current landscape.

The application of modeling and simulation techniques is increasingly common in preclinical stages of the drug discovery and development process. A survey focusing on preclinical pharmacokinetic/pharmacodynamics (PK/PD) analysis was conducted across pharmaceutical companies that are members of the International Consortium for Quality and Innovation in Pharmaceutical Development. Based on survey responses, ~68% of companies use preclinical PK/PD analysis in all therapeutic areas indicating its broad application. An important goal of preclinical PK/PD analysis in all pharmaceutical companies is for the selection/optimization of doses and/or dose regimens, including prediction of human efficacious doses. Oncology was the therapeutic area with the most PK/PD analysis support and where it showed the most impact. Consistent use of more complex systems pharmacology models and hybrid physiologically based pharmacokinetic models with PK/PD components was less common compared to traditional PK/PD models. Preclinical PK/PD analysis is increasingly being included in regulatory submissions with ~73% of companies including these data to some degree. Most companies (~86%) have seen impact of preclinical PK/PD analyses in drug development. Finally, ~59% of pharmaceutical companies have plans to expand their PK/PD modeling groups over the next 2 years indicating continued growth. The growth of preclinical PK/PD modeling groups in pharmaceutical industry is necessary to establish required resources and skills to further expand use of preclinical PK/PD modeling in a meaningful and impactful manner.

Quantitative Extrapolation: An Approach to Validation of Adult Drug Efficacy in Pediatric Subjects.

Confirmation of efficacy in pediatric drug development has traditionally required large, fully powered efficacy studies that have proven to have major feasibility and ethical challenges. Extrapolation of efficacy in the framework provided by the US Food and Drug Administration and European Medicines Agency is an appropriate solution when there is similarity of disease. When there is uncertainty regarding the degree of disease similarity, partial extrapolation may be utilized. The authors propose a more quantitative approach to partial extrapolation (ie, quantitative extrapolation), involving (1) integration of adult pharmacokinetic (PK), pharmacodynamic (PD), and clinical outcome data using pharmacometric models, (2) extrapolation using the adult pharmacometric model to predict PD and efficacy outcomes in pediatric subjects, and (3) validation of pediatric predictions with a streamlined plan of pediatric trials (ie, a quantitative extrapolation plan). A case study is presented for quantitative extrapolation using dipeptidyl peptidase 4 (DPP-4) inhibitors. In this example, the authors demonstrate how adult PK, PD, and HbA1c data can be integrated using a pharmacometric model for DPP-4 inhibitors with pediatric dose selection and efficacy validated with relatively few pediatric subjects.

Preclinical pharmacokinetics, dose proportionality, gender difference and protein binding study of 16-dehydropregnenolone, an antihyperlipidemic agent, in rats.

OBJECTIVES: This manuscript addresses key pharmacokinetic issues in support of the development of a potent candidate lipid-lowering drug molecule, 16-dehydropregnenolone (DHP). METHODS: Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) assay for simultaneous estimation of DHP and its metabolites, including 5-pregnene-3ß-ol-16, 17-epoxi-20-one (M(1) ) was validated in male and female Sprague-Dawley rat plasma and applied to different studies. Pharmacokinetic studies of DHP after intravenous and oral administration were carried out to assess any gender effect. Dose-proportionality after oral administration was assessed at three dose levels. Protein binding was estimated using the modified charcoal adsorption method. KEY FINDINGS: Rapid elimination of DHP from the systemic circulation resulted in a comparatively lesser systemic exposure in male compare to female rats. The area under the curve (AUC) after oral administration in males was significantly different to females. The large volume of distribution and low degree of protein binding suggest extensive distribution of DHP. An increase in the oral dose led to a disproportionate change in peak concentration (C(max) ) and AUC, indicating variable absorption. However, the dose-normalized AUC and C(max) at two dose levels were not found to be statistically different. CONCLUSIONS: The extent of conversion of DHP to M(1) was higher after oral administration in male rats but was insignificant in female rats. DHP showed low systemic oral bioavailability and exhibited dose-independent pharmacokinetics and gender differences.

The current role of model-based drug development.

IMPORTANCE OF THE FIELD: Current drug discovery and development programs are under growing scrutiny for low productivity and escalating costs. Model-based drug development (MBDD) has been recognized as a promising tool to address some of the related challenges. AREAS COVERED IN THIS REVIEW: This review introduces the concept of MBDD and the associated quantitative pharmacology-based iterative 'learn and confirm' paradigm in the drug discovery and development process to provide concise information for rational decision making. It summarizes the evolving role of MBDD in drug development programs and outlines the full armamentarium of modeling and simulation approaches utilized to facilitate its application. WHAT THE READER WILL GAIN: Different aspects and applications of MBDD are introduced to the reader and illustrated in prime examples. The reader is provided with an understanding of potential applications of MBDD in drug development as well as the associated limitations and challenges in its implementation. TAKE HOME MESSAGE: MBDD is a tool that is increasingly used throughout the drug discovery and development continuum to support fast and rationale decision making and has thereby the potential to accelerate and increase the cost-effectiveness of the drug development process.

Assessment of systemic interaction between Swertia chirata extract and its Bioactive constituents in rabbits.

The plant Swertia chirata (Gentianaceae) is known for its multifarious medicinal value in the Indian system of medicine (Ayurveda). Its methanol extracts having antidiabetic activity contains mangiferin, amarogentin, amaroswerin, sweroside and swertiamarin as active constituents. The pharmacokinetics of mangiferin and amarogentin have been carried out after intravenous administration of pure standards and extract from S. chirata (CT) in rabbits to assess systemic interaction. The remaining three components were also monitored in plasma for pharmacokinetic estimation based on the ratio analysis method. Mangiferin was characterized by a relative low clearance ( approximately 0.14 L/h/kg) and a lesser volume of distribution ( approximately 0.15 L/kg), while amarogentin exhibited a rapid clearance ( approximately 2.62 L/h/kg) and wide distribution ( approximately 1.08 L/kg) from the systemic circulation. No significant difference was observed in pharmacokinetic parameters of mangiferin and amarogentin either administered alone or as CT formulation in rabbits.

Simultaneous estimation of mangiferin and four secoiridoid glycosides in rat plasma using liquid chromatography tandem mass spectrometry and its application to pharmacokinetic study of herbal preparation.

Extracts from Swertia chirata (family Gentianaceae) have antidiabetics and antioxidant activity, largely attributed to the flavonoids and secoiridoids, which are a major class of functional components in methanolic extracts from aerial part of plants. In order to facilitate analysis of systemic exposure to S. chirata derived products in animals, we developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) based method that is capable of routinely monitoring plasma levels of flavonoids and secoiridoids. An LC-MS/MS-based method has been developed for the simultaneous estimation of two bioactive markers, mangiferin and amarogentin along with three other components, amaroswerin, sweroside and swertiamarin in rat plasma. All the analytes including the internal standard (kutkoside) were chromatographed on RP-18 column (250 mm x 4 mm i.d., 5 microm.) coupled with guard column using acetonitrile: 0.5 mM ammonium acetate buffer, pH approximately 3.0 as mobile phase at a flow rate of 1 ml/min in gradient mode. The final flow to source was splitted in 1:1 ratio. The detection of the analytes was performed on API 4000 LC-MS/MS system in the multiple reaction-monitoring (MRM) mode. The quantitation for analytes other than the pure markers was based on relative concentration. The method was validated in terms of establishing linearity, specificity, sensitivity, recovery, accuracy and precision (Intra- and Inter-day), freeze-thaw stability, peltier stability, dry residue stability and long-term stability. The recoveries from spiked control samples were >90% for all analytes and internal standard except mangiferin where recovery was >60%. Intra- and inter-day accuracy and precision of the validated method were within the acceptable limits of <15% at low and <10% at other concentrations. The quantitation method was successfully applied to generate pharmacokinetic (PK) profile of markers as well as to detect other components in plasma after intravenous dose administration of herbal preparation in male Sprague-Dawley (SD) rats.

Liquid chromatography/tandem mass spectrometric study and analysis of xanthone and secoiridoid glycoside composition of Swertia chirata, a potent antidiabetic.

Swertia chirata is a bitter plant, used in the Indian system of medicine (Ayurveda) for various human ailments. The bioactive constituents include the xanthone and secoiridoid glycosides consisting of mangiferin, amarogentin, amaroswerin, sweroside and swertiamarin. Methanolic extracts of S. chirata possess constituents with antidiabetic activities, which was investigated by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Preliminary HPLC analyses were performed on a reversed-phase C18 column using gradient elution. In the LC/ESI-MS spectra, predominant [M+H]+ and [M+Na]+ ions were observed in positive ion mode and provided molecular mass information. The five components of S. chirata were structurally correlated and confirmed based on the fragmentation characteristics and information available in the literature. The fragmentation behavior of [M+H]+/[M+Na]+ ions of these components were deduced from the collision-induced dissociation (CID) spectra obtained from the selective on-column information-dependant acquisition (IDA) approach. Xanthone-C-glycoside showed characteristic fragment ions due to fragmentation in the C-glycosidic unit while iridoid-O-glycosides showed characteristic fragment ions due to cleavage in the glycoside linkage and retro-Diels-Alder (RDA) cleavage within an iridoid aglycone. Furthermore, on the basis of this information, an analytical assay was developed and validated to determine relative concentrations of mangiferin, amarogentin, amaroswerin, sweroside and swertiamarin. The detection was carried out using multiple reaction monitoring (MRM) in positive ionization mode with a total analysis time of 3.5 min. The method was successfully applied to standardize four different batches of herbal preparation on the basis of relative concentration of five bioactive components.

A sensitive and selective HPLC/ESI-MS/MS assay for the simultaneous quantification of 16-dehydropregnenolone and its major metabolites in rabbit plasma.

A sensitive, selective and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric assay was developed and validated for the simultaneous quantification of 16-dehydropregnenolone (DHP) and its five metabolites 4,16-pregnadien-3, 20-dione (M(1)), 5-pregnene-3beta-ol-20-one (M(2)), 5-pregnene-3beta, 20-diol (M(3)), 5-pregnene-3beta-ol-16, 17-epoxi-20-one (M(4)) and 5,16-pregnadien-3beta, 11-diol-20-one (M(5)) in rabbit plasma using dexamethasone as internal standard (IS). The analytes were chromatographed on Spheri-5 RP-18 column (5 microm, 100 mm x 4.6 mm i.d.) coupled with guard column using acetonitrile:ammonium acetate buffer (90:10, v/v) as mobile phase at a flow rate of 0.65 ml/min. The quantitation of the analytes was carried out using API 4000 LC-MS-MS system in the multiple reaction monitoring (MRM) mode. The method was validated in terms of linearity, specificity, sensitivity, recovery, accuracy, precision (intra- and inter-assay variation), freeze-thaw, long-term, auto injector and dry residue stability. Linearity in plasma was observed over a concentration range of 1.56-400 ng/ml with a limit of detection (LOD) of 0.78 ng/ml for all analytes except M(3) and M(5) where linearity was over the 3.13-400 ng/ml with LOD of 1.56 ng/ml. The absolute recoveries from plasma were consistent and reproducible over the linearity range for all analytes. The intra- and inter-day accuracy and precision method were within the acceptable limits and the analytes were stable after three freeze-thaw cycles and their dry residues were stable at -60 degrees C for 15 days. The method was successfully applied to determine concentrations of DHP and its putative metabolites in plasma during a pilot pharmacokinetic study in rabbits.