Pharmacokinetics and safety of coformulated bictegravir, emtricitabine, and tenofovir alafenamide in children aged 2 years and older with virologically suppressed HIV: a phase 2/3, open-label, single-arm study

BACKGROUND

Coformulated bictegravir, emtricitabine, and tenofovir alafenamide is a single-tablet regimen and was efficacious and well tolerated in children and adolescents with HIV (aged 6 years to <18 years) in a 48-week phase 2/3 trial. In this study, we report data from children aged at least 2 years and weighing 14 kg to less than 25 kg.

METHODS

We conducted this open-label, multicentre, multicohort, single-arm study in South Africa, Thailand, Uganda, and the USA. Participants were virologically suppressed children with HIV, aged at least 2 years, weighing 14 kg to less than 25 kg. Participants received bictegravir (30 mg), emtricitabine (120 mg), and tenofovir alafenamide (15 mg) once daily, switching to bictegravir (50 mg), emtricitabine (200 mg), and tenofovir alafenamide (25 mg) upon attaining a bodyweight of at least 25 kg. The study included pharmacokinetic evaluation at week 2 to confirm the dose of coformulated bictegravir, emtricitabine, and tenofovir alafenamide for this weight band by comparing with previous adult data. Primary outcomes were bictegravir area under the curve over the dosing interval (AUCtau) and concentration at the end of the dosing interval (Ctau) at week 2, and incidence of treatment-emergent adverse events and laboratory abnormalities until the end of week 24 in all participants who received at least one dose of bictegravir, emtricitabine, and tenofovir alafenamide. This study is registered with ClinicalTrials.gov, NCT02881320.

FINDINGS

Overall, 22 participants were screened (from Nov 14, 2018, to Jan 11, 2020), completed treatment with bictegravir, emtricitabine, and tenofovir alafenamide (until week 48), and entered an extension phase. The geometric least squares mean (GLSM) ratio for AUCtau for bictegravir was 7·6% higher than adults (GLSM ratio 107·6%, 90% CI 96·7-119·7); Ctau was 34·6% lower than adults (65·4%, 49·1-87·2). Both parameters were within the target exposure range previously found in adults, children, or both". Grade 3-4 laboratory abnormalities occurred in four (18%) participants by the end week 24 and six (27%) by the end of week 48. Drug-related adverse events occurred in three participants (14%) by the end of week 24 and week 48; none were severe. No Grade 3-4 adverse events, serious adverse events, or adverse events leading to discontinuation occurred by the end of week 24 and week 48.

INTERPRETATION

Data support the use of single-tablet coformulated bictegravir (30 mg), emtricitabine (120 mg), and tenofovir alafenamide (15 mg) for treatment of HIV in children aged at least 2 years and weighing 14 kg to less than 25 kg.

FUNDING

Gilead Sciences.

Pharmacokinetics and Safety of Lurbinectedin Administrated with Itraconazole in Cancer Patients: A Drug-Drug Interaction Study

This open-label, two-part, phase Ib drug-drug interaction study investigated whether the pharmacokinetic (PK) and safety profiles of lurbinectedin (LRB), a marine-derived drug, are affected by co-administration of itraconazole (ITZ), a strong CYP3A4 inhibitor, in adult patients with advanced solid tumors. In Part A, three patients were sequentially assigned to Sequence 1 (LRB 0.8 mg/m2, 1-h intravenous [IV] + ITZ 200 mg/day oral in Cycle 1 [C1] and LRB alone 3.2 mg/m2, 1 h, IV in Cycle 2 [C2]). In Part B, 11 patients were randomized (1:1) to receive either Sequence 1 (LRB at 0.9 mg/m2 + ITZ in C1 and LRB alone in C2) or Sequence 2 (LRB alone in C1 and LRB + ITZ in C2). Eleven patients were evaluable for PK analysis: three in Part A and eight in Part B (four per sequence). The systemic total exposure of LRB increased with ITZ co-administration: 15% for Cmax, area under the curve (AUC) 2.4-fold for AUC0-t and 2.7-fold for AUC0-∞. Co-administration with ITZ produced statistically significant modifications in the unbound plasma LRB PK parameters. The LRB safety profile was consistent with the toxicities described in previous studies. Co-administration with multiple doses of ITZ significantly altered LRB systemic exposure. Hence, to avoid LRB overexposure when co-administered with strong CYP3A4 inhibitors, an LRB dose reduction proportional to CL reduction should be applied.

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.

Use of toxicokinetic data for afidopyropen to determine the dose levels in developmental toxicity studies

Afidopyropen is an insecticide that acts as a TRPV channel modulator in chordotonal organs of target insects and has been assessed for a wide range of toxicity endpoints including developmental toxicity in rats and rabbits. The GLP developmental toxicity study in rabbits did not produce evidence of maternal or fetal toxicity at the highest dose tested (32 mg/kg/day) but pharmacokinetics (PK) in pregnant rabbits in this study exhibited onset of PK nonlinearity from 5 mg/kg/day on, as measured by plasma C_max and AUC. The NOAEL (32 mg/kg/day) is 9000X higher than maximum expected human dietary exposures to afidopyropen; the dose range where nonlinear PK were observed (5-15 mg/kg/day) is 1400-4200X higher. As nonlinearity occurred between 5 and 15 mg/kg/day, 32 mg/kg/day is concluded to be a sufficiently high dose (kinetically derived maximum dose) for a prenatal developmental toxicity study. As recognized by regulatory dose-selection guidance, onset of saturated PK is evidence of excessive biological stress to test animals rendering any effects at such doses of questionable relevance for human risk assessment. These data demonstrate that consideration of PK is critical for improving the dose-selection in developmental toxicity studies to enhance human relevance of animal toxicity studies.

Drug-Drug Interaction Studies Between Hepatitis C Virus Antivirals Sofosbuvir/Velpatasvir and Boosted and Unboosted Human Immunodeficiency Virus Antiretroviral Regimens in Healthy Volunteers

Background

Combining antiviral regimens in the hepatitis C virus (HCV)/human immunodeficiency virus (HIV)-coinfected population can be complex as they share overlapping mechanisms for elimination that may result in drug interactions. The pharmacokinetics, safety, and tolerability of sofosbuvir/velpatasvir (SOF/VEL) with multiple antiretroviral (ARV) regimens were evaluated.

Methods

Healthy volunteers were enrolled into 2 phase 1, open-label, randomized, multiple-dose, cross-over studies. SOF/VEL and ARV regimens were administered alone and in combination; ARVs (and pharmacokinetic enhancers) included atazanavir (ATV), cobicistat (COBI), darunavir (DRV), dolutegravir (DTG), efavirenz (EFV), elvitegravir (EVG), emtricitabine (FTC), lopinavir (LPV), raltegravir (RAL), rilpivirine (RPV), ritonavir (RTV), tenofovir alafenamide (TAF), and tenofovir disoproxil fumarate (TDF). Geometric least squares means ratios (coadministration:alone) and 90% confidence intervals were constructed for area under the plasma concentration-time curve over the dosing interval, maximum concentration, and trough, for all analytes. Safety and tolerability were also evaluated.

Results

In total, 237 participants were enrolled. No clinically relevant differences in the pharmacokinetics (PK) of SOF, SOF metabolite GS-331007, or VEL were observed other than an approximate 50% decrease in VEL exposure when administered with EFV/FTC/TDF. No clinically relevant differences in the PK of ARVs were observed when administered with SOF/VEL. Study treatments were well tolerated, including no observed creatinine clearance changes during evaluation of TDF-containing regimens.

Conclusions

SOF/VEL and ARV regimens including ATV, COBI, DRV, DTG, EVG, FTC, LPV, RAL, RPV, RTV, TAF, or TDF may be coadministered without dose adjustment. Use of SOF/VEL with EFV-containing regimens is not recommended due to an approximate 50% reduction in VEL exposure.

Phenotype-Based Screens with Conformation-Specific Inhibitors Reveal p38 Gamma and Delta as Targets for HCC Polypharmacology

The approved kinase inhibitors for hepatocellular carcinoma (HCC) are not matched to specific mutations within tumors. This has presented a daunting challenge; without a clear target or mechanism, no straightforward path has existed to guide the development of improved therapies for HCC. Here, we combine phenotypic screens with a class of conformation-specific kinase inhibitors termed type II to identify a multikinase inhibitor, AD80, with antitumoral activity across a variety of HCC preclinical models, including mouse xenografts. Mass spectrometry profiling found a number of kinases as putative targets for AD80, including several receptor and cytoplasmic protein kinases. Among these, we found p38 gamma and delta as direct targets of AD80. Notably, a closely related analog of AD80 lacking p38δ/γ activity, but retaining several other off-target kinases, lost significant activity in several HCC models. Moreover, forced and sustained MKK6 → p38→ATF2 signaling led to a significant reduction of AD80 activity within HCC cell lines. Together with HCC survival data in The Cancer Genome Atlas and RNA-seq analysis, we suggest p38 delta and gamma as therapeutic targets in HCC and an "AD80 inhibition signature" as identifying those patients with best clinical outcomes.

Pharmacokinetics of HIV-Integrase Inhibitors During Pregnancy: Mechanisms, Clinical Implications and Knowledge Gaps

Prevention of mother-to-child transmission of HIV and optimal maternal treatment are the most important goals of antiretroviral therapy in pregnant women with HIV. These goals may be at risk due to possible reduced exposure during pregnancy caused by physiological changes. Limited information is available on the impact of these physiological changes. This is especially true for HIV-integrase inhibitors, a relatively new class of drugs, recommended first-line agents and hence used by a large proportion of HIV-infected patients. Therefore, the objective of this review is to provide a detailed overview of the pharmacokinetics of HIV-integrase inhibitors in pregnancy. Second, this review defines potential causes for the change in pharmacokinetics of HIV-integrase inhibitors during pregnancy. Despite increased clearance, for raltegravir 400 mg twice daily and dolutegravir 50 mg once daily, exposure during pregnancy seems adequate; however, for elvitegravir, the proposed minimal effective concentration is not reached during pregnancy. Lower exposure to these drugs may be caused by increased hormone levels and, subsequently, enhanced drug metabolism during pregnancy. The pharmacokinetics of bictegravir and cabotegravir, which are under development, have not yet been evaluated in pregnant women. New studies need to prospectively assess whether adequate exposure is reached in pregnant women using these new HIV-integrase inhibitors. To further optimize antiretroviral treatment in pregnant women, studies need to unravel the underlying mechanisms behind the changes in the pharmacokinetics of HIV-integrase inhibitors during pregnancy. More knowledge on altered pharmacokinetics during pregnancy and the underlying mechanisms contribute to the development of effective and safe antiretroviral therapy for HIV-infected pregnant women.

Treatment with HC-070, a potent inhibitor of TRPC4 and TRPC5, leads to anxiolytic and antidepressant effects in mice

Background

Forty million adults in the US suffer from anxiety disorders, making these the most common forms of mental illness. Transient receptor potential channel canonical subfamily (TRPC) members 4 and 5 are non-selective cation channels highly expressed in regions of the cortex and amygdala, areas thought to be important in regulating anxiety. Previous work with null mice suggests that inhibition of TRPC4 and TRPC5 may have anxiolytic effects.

HC-070 in vitro

To assess the potential of TRPC4/5 inhibitors as an avenue for treatment, we invented a highly potent, small molecule antagonist of TRPC4 and TRPC5 which we call HC-070. HC-070 inhibits recombinant TRPC4 and TRPC5 homomultimers in heterologous expression systems with nanomolar potency. It also inhibits TRPC1/5 and TRPC1/4 heteromultimers with similar potency and reduces responses evoked by cholecystokinin tetrapeptide (CCK-4) in the amygdala. The compound is >400-fold selective over a wide range of molecular targets including ion channels, receptors, and kinases.

HC-070 in vivo

Upon oral dosing in mice, HC-070 achieves exposure levels in the brain and plasma deemed sufficient to test behavioral activity. Treatment with HC-070 attenuates the anxiogenic effect of CCK-4 in the elevated plus maze (EPM). The compound recapitulates the phenotype observed in both null TRPC4 and TRPC5 mice in a standard EPM. Anxiolytic and anti-depressant effects of HC-070 are also observed in pharmacological in vivo tests including marble burying, tail suspension and forced swim. Furthermore, HC-070 ameliorates the increased fear memory induced by chronic social stress. A careful evaluation of the pharmacokinetic-pharmacodynamic relationship reveals that substantial efficacy is observed at unbound brain levels similar to, or even lower than, the 50% inhibitory concentration (IC₅₀) recorded in vitro, increasing confidence that the observed effects are indeed mediated by TRPC4 and/or TRPC5 inhibition. Together, this experimental data set introduces a novel, high quality, small molecule antagonist of TRPC4 and TRPC5 containing channels and supports the targeting of TRPC4 and TRPC5 channels as a new mechanism of action for the treatment of psychiatric symptoms.

Phase I clinical and pharmacokinetic study of PM01183 (a tetrahydroisoquinoline, Lurbinectedin) in combination with gemcitabine in patients with advanced solid tumors

Background To determine the recommended dose (RD) of a combination of PM01183 and gemcitabine in patients with advanced solid tumors. Methods Forty-five patients received escalating doses of PM01183/gemcitabine on Days 1 and 8 every 3 weeks (d1,8 q3wk) following a standard 3 + 3 design. Results PM01183 3.5 mg flat dose (FD)/gemcitabine 1000 mg/m² was the highest dose level tested. Dose-limiting toxicities (DLTs) were mostly hematological and resulted in the expansion of a lower dose level (PM01183 3.5 mg FD/gemcitabine 800 mg/m²); 19 patients at this dose level were evaluable but >30% had DLT and >20% had febrile neutropenia. No DLT was observed in 11 patients treated at PM01183 3.0 mg FD/gemcitabine 800 mg/m², which was defined as the RD. This regimen was feasible and tolerable with manageable toxicity; mainly grade 3/4 myelosuppression. Non-hematological toxicity comprised fatigue, nausea, vomiting, and transaminases increases. Fifteen (33%) patients received ≥6 cycles with no cumulative hematological toxicity. Pharmacokinetic analysis showed no evidence of drug-drug interaction. Nine of 38 patients had response as per RECIST (complete [3%] and partial [21%]), for an overall response rate (ORR) of 24% (95% Confidence Interval [CI] 12-40%). Eleven patients (29%) had disease stabilization ≥4 months. Responses were durable (median of 8.5 months): overall median progression-free survival (PFS) was 4.2 months (95% CI, 2.7-6.5 months). Conclusions The RD for this combination is PM01183 3.0 mg FD (or 1.6 mg/m²)/gemcitabine 800 mg/m² d1,8 q3wk. This schedule is well tolerated and has antitumor activity in several advanced solid tumor types.

First-In-Class Small Molecule ONC201 Induces DR5 and Cell Death in Tumor but Not Normal Cells to Provide a Wide Therapeutic Index as an Anti-Cancer Agent

We previously identified ONC201 (TIC10) as a first-in-class orally active small molecule with robust antitumor activity that is currently in clinical trials in advanced cancers. Here, we further investigate the safety characteristics of ONC201 in preclinical models that reveal an excellent safety profile at doses that exceed efficacious doses by 10-fold. In vitro studies indicated a strikingly different dose-response relationship when comparing tumor and normal cells where maximal effects are much stronger in tumor cells than in normal cells. In further support of a wide therapeutic index, investigation of tumor and normal cell responses under identical conditions demonstrated large apoptotic effects in tumor cells and modest anti-proliferative effects in normal cells that were non-apoptotic and reversible. Probing the underlying mechanism of apoptosis indicated that ONC201 does not induce DR5 in normal cells under conditions that induce DR5 in tumor cells; DR5 is a pro-apoptotic TRAIL receptor previously linked to the anti-tumor mechanism of ONC201. GLP toxicology studies in Sprague-Dawley rats and beagle dogs at therapeutic and exaggerated doses revealed no dose-limiting toxicities. Observations in both species at the highest doses were mild and reversible at doses above 10-fold the expected therapeutic dose. The no observed adverse event level (NOAEL) was ≥42 mg/kg in dogs and ≥125 mg/kg in rats, which both correspond to a human dose of approximately 1.25 g assuming standard allometric scaling. These results provided the rationale for the 125 mg starting dose in dose escalation clinical trials that began in 2015 in patients with advanced cancer.

Developing an activity and absorption-based quality control platform for Chinese traditional medicine: Application to Zeng-Sheng-Ping(Antitumor B)

ETHNOPHARMACOLOGICAL RELEVANCE

Zeng-Sheng-Ping (ZSP), also called antitumor B, is a marketed Chinese traditional medicine used for cancer prevention.

AIM OF THE STUDY

Currently, for the quality control of Chinese traditional medicines, marker compounds are not selected based on bioactivities and pharmaceutical behaviors in most of the cases. Therefore, even if the "quality" of the medicine is controlled, the pharmacological effect could still be inconsistent. The aim of this study is to establish an activity and absorption-based platform to select marker compound(s) for the quality control of Chinese traditional medicines.

MATERIALS AND METHODS

We used ZSP as a reference Chinese traditional medicine to establish the platform. Activity guided fractionation approach was used to purify the major components from ZSP. NMR and MS spectra were used to elucidate the structure of the isolated compounds. MTT assay against oral carcinoma cell line (SCC2095) was performed to evaluate the activities. UPLC-MS/MS was used to quantify the pure compounds in ZSP and the active fraction. The permeabilities of the identified compounds were evaluated in the Caco-2 cell culture model. The intracellular accumulation of the isolated compounds was evaluated in the SCC2095 cells.

RESULTS

The major compounds were identified from ZSP. The contents, anti-proliferation activities, permeabilities, and intracellular accumulations of these compounds were also evaluated. The structure of these purified compounds were identified by comparing the NMR and MS data with those of references as rutaevine (1), limonin (2), evodol (3), obacunone (4), fraxinellone (5), dictamnine (6), maackiain (7), trifolirhizin (8), and matrine (9). The IC50 of compounds 5, 6, and 7 against SCC2095 cells were significantly lower than that of ZSP. The uptake permeability of compounds 5, 6, and 7 were 2.58 ± 0.3 × 10(-5), 4.33 ± 0.5 × 10(-5), and 4.27 ± 0.8 × 10(-5) respectively in the Caco-2 cell culture model. The intracellular concentrations of these compounds showed that compounds 5, 6, and 7 were significantly accumulated inside the cells.

CONCLUSION

Based on the activity against oral carcinoma cell line as well as the absorption permeability, compound 5, 6, and 7 are selected as quality control markers for ZSP. An activity and absorption-based platform was established and successfully used for the quality control of ZSP.

Phase I dose-escalation studies of SNX-5422, an orally bioavailable heat shock protein 90 inhibitor, in patients with refractory solid tumours

BACKGROUND

Orally administered SNX-5422, a novel, selective prodrug of the Heat shock protein 90 (Hsp90) inhibitor SNX-2112, was investigated in two sequential phase I studies to determine the safety, maximum tolerated doses (MTDs) and pharmacokinetic profile of SNX-5422.

METHODS

Using a dose-escalation design, 3-6 adults with advanced solid tumours received SNX-5422 every-other-day (QOD) or once-daily (QD) 3weeks on/1week off or QD continuously, with disease assessments every 8 weeks. Single-dose and steady-state pharmacokinetic parameters of SNX-2112 were determined.

RESULTS

In total, 56 patients were enrolled: QOD 3 weeks on/1 week off, n=36; QD 3weeks on/1 week off, n=17; QD continuous, n=3. Doses ranged from 4 to 133mg/m(2) QOD and 50 to 89 mg/m(2) QD. The MTDs were defined as 100mg/m(2) QOD and 67 mg/m(2) QD, respectively, with diarrhoea being dose-limiting on both 3 weeks on/1 week off schedules. Overall, treatment-related adverse events were mainly low grade, including diarrhoea (64%), nausea (39%), fatigue (28%), and vomiting (28%). Reversible grade 1-3 nyctalopia (night blindness) was reported by four patients (dose: 50-89mg/m(2) QD; 100mg/m(2) QOD). Exposure was generally linear, though greater than dose-proportional. Of 32 evaluable patients on QOD dosing, there was one durable complete response (prostate cancer), one confirmed (HER2+breast cancer) and one unconfirmed partial response (adrenal gland cancer). Three patients (QOD schedule) had stable disease for ⩾ 6 months.

CONCLUSIONS

The dose and schedule recommended for further study with SNX-5422 is 100mg/m(2) QOD 3 weeks on/1 week off based on improved tolerability and preliminary evidence of clinical activity.

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.

Preclinical metabolism and pharmacokinetics of SB1317 (TG02), a potent CDK/JAK2/FLT3 inhibitor

SB1317 (TG02) is a novel small molecule potent CDK/JAK2/FLT3 inhibitor. To evaluate full potential of this development candidate, we conducted drug metabolism and pharmacokinetic studies of this novel anti-cancer agent. SB1317 was soluble, highly permeable in Caco-2 cells, and showed > 99% binding to plasma from mice, dog and humans. It was metabolically stable in human and dog liver microsomes relative to mouse and rat. SB1317 was mainly metabolized by CYP3A4 and CY1A2 in vitro. SB1317 did not inhibit any of the major human CYPs in vitro except CYP2D6 (IC50=1 μM). SB1317 did not significantly induce CYP1A and CYP3A4 in human hepatocytes in vitro. The metabolic profiles in liver microsomes from preclinical species were qualitatively similar to humans. In pharmacokinetic studies SB1317 showed moderate to high systemic clearance (relative to liver blood flow), high volume of distribution ( > 0.6 L/kg), oral bioavailability of 24%, ∼ 4 and 37% in mice, rats and dogs, respectively; and extensive tissue distribution in mice. The favorable ADME of SB1317 supported its preclinical development as an oral drug candidate.

Interaction of a cyclostreptin analogue with the microtubule taxoid site: the covalent reaction rapidly follows binding

The natural product cyclostreptin reacts covalently and stoichiometrically with microtubules, at either of two amino acid residues of beta-tubulin, Thr-218 or Asn-226, but much less extensively and only at Thr-218 in unpolymerized tubulin. It was found that 8-acetylcyclostreptin (8AcCS) induces tubulin assembly in a manner almost identical with that of cyclostreptin. We therefore synthesized [ (14)C-acetyl]8AcCS and studied the kinetics of its interaction with glutaraldehyde-stabilized microtubules and with unassembled tubulin. With the microtubules, we found that 8AcCS bound rapidly, with a minimal (unmeasurable with the radiolabeled analogue) lag prior to the occurrence of the covalent reaction. Apparent reaction rate constants for the overall reaction ranged from 6.2 x 10 (2) M (-1) s (-1) at 0 degrees C to 5.6 x 10 (3) M (-1) s (-1) at 20 degrees C. The rate constants obtained at 0 and 10 degrees C indicate an activation energy for the reaction of about 27 kcal/mol, while those obtained at 10 and 20 degrees C indicate an activation energy of about 7.7 kcal/mol. With the unpolymerized tubulin, we did find a minimal covalent reaction occurred without apparent microtubule assembly, but a substantial reaction only occurred following assembly. In conclusion, the radiolabeled 8AcCS shows that an extensive covalent interaction of ligand with tubulin requires microtubule assembly and that the covalent reaction occurs rapidly after the initial binding interaction.

WMC-79, a potent agent against colon cancers, induces apoptosis through a p53-dependent pathway

WMC-79 is a synthetic agent with potent activity against colon and hematopoietic tumors. In vitro, the agent is most potent against colon cancer cells that carry the wild-type p53 tumor suppressor gene (HCT-116 and RKO cells: GI50<1 nmol/L, LC50 approximately 40 nmol/L). Growth arrest of HCT-116 and RKO cells occurs at the G1 and G2-M check points at sublethal concentrations (10 nmol/L) but the entire cell population was killed at 100 nmol/L. WMC-79 is localized to the nucleus where it binds to DNA. We hypothesized that WMC-79 binding to DNA is recognized as an unrepairable damage in the tumor cells, which results in p53 activation. This triggers transcriptional up-regulation of p53-dependent genes involved in replication, cell cycle progression, growth arrest, and apoptosis as evidenced by DNA microarrays. The change in the transcriptional profile of HCT-116 cells is followed by a change in the levels of cell cycle regulatory proteins and apoptosis. The recruitment of the p53-dependent apoptosis pathway was suggested by the up-regulation of p53, p21, Bax, DR-4, DR-5, and p53 phosphorylated on Ser15; down-regulation of Bcl-2; and activation of caspase-8, -9, -7, and -3 in cells treated with 100 nmol/L WMC-79. Apoptosis was also evident from the flow cytometric studies of drug-treated HCT-116 cells as well as from the appearance of nuclear fragmentation. However, whereas this pathway is important in wild-type p53 colon tumors, other pathways are also in operation because colon cancer cell lines in which the p53 gene is mutated are also affected by higher concentrations of WMC-79.

Oxidative metabolism by P450 and function coupling to efflux systems: Modulation of mycotoxin toxicity

Man is permanently exposed to exogenous substances, either natural ones (e.g. mycotoxins, plant extracts) or man-made compounds such as pesticides or drugs. In some cases, such foreign compounds can exert either therapeutic (drugs) or toxic effects, or both. In particular, fungi are the source of a number of different secondary metabolites having such therapeutic or toxic effects. The efficiency or toxicity of foreign compounds depends on their ability to cross the cytoplasmic membrane. The exogenous molecules subsequently bind to their specific receptor in the cytoplasm or nucleus of the cell, but they are also attacked by the detoxification proteins, which in mammals are mainly composed of two types of membrane enzyme systems: cytochrome P450s, which functionalize hydrophobic xenobiotics, and an active P-glycoprotein (P-gp) transport system involved in the efflux of xenobiotics. These processes are illustrated through the use of two fungal cyclopeptides, cyclosporin A (CsA) and roquefortine C. The former, CsA, is known to be an immunosuppressor, while the latter, roquefortine C, is a potentially neurotoxic compound. CsA inhibits P-gp in a different way from its metabolites, whereas roquefortine C activates P-gp and also inhibits P450-3A and other haemoproteins. The current observations show that the two detoxification systems complement each other, resulting in a given toxicity level. The two mammal enzyme systems might therefore prove useful in the development of toxicity screening procedures.

Synthesis and chloroquine-enhancing activity of Na-deacetyl-ferrocenoyl-strychnobrasiline

Several strychnobrasiline derivatives have been synthesized to overcome the lack of in vivo reversal activity of the parent compound. In the present study, N(a)-deacetyl-ferrocenoyl-strychnobrasiline was synthesized by condensing N(a)-deacetyl-strychnobrasiline with ferrocenic acid previously treated with oxalyl chloride. While the in vitro antiplasmodial activity of the test compound (IC(50)=4.83 microg/mL) was increased 15-fold compared to that of strychnobrasiline, and the in vitro enhancing activity was found to be similar to that of the parent compound, the compound was devoid of any in vivo potentiating effect, and an antagonistic effect was even observed at higher doses. Based on the overall results on the hemisynthesis of strychnobrasiline derivatives for better reversal activity, this strategy has appeared to be of little value for useful drugs.

Estrogen receptor ligands. Part 4: The SAR of the syn-dihydrobenzoxathiin SERAMs

A series of estrogen receptor ligands based on a dihydrobenzoxathiin scaffold is described and evaluated for estrogen/anti-estrogen activity in both in vitro and in vivo models. The most active analogue, 22, was found to be 40-fold ERalpha selective in a competitive binding assay, and 22 demonstrated very potent in vivo antagonism of estradiol driven proliferation in an immature rat uterine weight gain assay.

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%.

Phototoxicity and photoinactivation of blebbistatin in UV and visible light

Blebbistatin was recently identified as a selective, cell-permeant inhibitor of myosin II. Because blebbistatin is likely to be used extensively with fluorescence imaging in studies of cytoskeletal dynamics, its compatibility with common excitation wavelengths was examined. Illumination of blebbistatin-treated bovine aortic endothelial cells at 365 and 450-490 nm, but not 510-560 or 590-650 nm, caused dose-dependent cell death. Illumination of blebbistatin alone at 365 and 450-490 nm changed its absorption and emission spectra, but the resultant compounds were not toxic. In addition, photoreacted blebbistatin no longer disrupted myosin distribution in cells, indicating loss of pharmacological activity. Fluorescence microscopy showed that upon illumination, blebbistatin became bound to cells and to protein-coated glass, suggesting that toxicity may arise from light-induced reaction of blebbistatin with cell proteins. Blebbistatin should be used only with careful consideration of these photochemical effects.

Hydration, stability, and phase transformations of a new antitumor drug

We studied hydration equilibria and phase transformations in a cytotoxic drug (BBR3576). The original sample is a hydrated compound that undergoes a structural phase transition when it looses about half of its structural water. Such a structural transition is completely reversible: the partially dehydrated form is stable up to 130 degrees C (or up to 140 degrees C for several minutes) and reverts to the original form upon rehydration. Completely different phase relationships are observed if an original sample is fully dehydrated: when all water has been released, a metastable anhydrous phase forms, which undergoes an irreversible exothermic conversion to a stable phase. Upon rehydration at room temperature of such an anhydrous phase, a new hydrated form is obtained, which is definitely different from the original one.

Discovery and SAR of potent, orally available and brain-penetrable 5,6-dihydro-4H-3-thia-1-aza-benzo[e]azulen- and 4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulen derivatives as neuropeptide Y Y5 receptor antagonists

Combination of structural elements from a potent Y5 antagonist (2) with thiazole fragments that exhibit weak Y5 affinities followed by lead optimisation led to the discovery of (5,6-dihydro-4H-3-thia-1-aza-benzo[e]azulen-2-yl)-piperidin-4-ylmethyl-amino and (4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulen-2-yl)-piperidin-4-ylmethyl-amino derivatives. Both classes of compounds are capable of delivering potent and selective orally and centrally bioavailable NPY Y5 receptor antagonists.

Phase I clinical and pharmacokinetic study of BBR 3576, a novel aza-anthrapyrazole, administered i.v. every 4 weeks in patients with advanced solid tumors: a phase I study group trial of the Central European Society of Anticancer-Drug Research (CESAR)

BBR 3576 is a novel aza-anthrapyrazole with limited potential for cardiotoxicity in preclinical models. This phase I clinical and pharmacokinetic study was performed to determine the maximum tolerated dose, the dose-limiting toxicity (DLT) and the pharmacokinetic profile of BBR 3576 administered i.v. as a 1-h infusion repeated every 4 weeks. In total, 27 patients were treated at doses starting from 1 to 150 mg/m2. The dose levels 1, 2, 4, 8, 16, 32, 64, 90, 125 and 150 mg/m2 were investigated in one, three, one, three, two, one, three, four, three and six patients, respectively. The DLT was a grade 3 stomatitis at 150 mg/m2. At this dose level as well as at 125 mg/m2, neutropenia grade 3 and 4 were frequently seen, but not reaching the criteria for DLT. Time to neutrophil nadir was about 2 weeks and recovery took place within 1 week. Other bone marrow toxicities were mild; lymphopenia was also observed. No significant drug-induced cardiotoxicity was observed. The plasma concentration versus time curves of BBR 3576 showed a biexponential profile with a linear kinetic behavior. A very large volume of distribution, a high plasma clearance and long elimination half-lives were calculated. Renal unchanged drug excretion was less than 10% and therefore a minor excretion route. No objective antitumor responses were found. On the basis of this study, the recommended dose for phase II studies is 150 mg/m2, although the maximum tolerated dose as per protocol definition was not reached. This trial showed that BBR 3576 has a manageable toxicity profile on a 4-week schedule. Phase II studies have started in patients with solid tumors, as suggested by preclinical data in different in vivo model systems.

Microbial transformation of baccatin VI and 1β-Hydroxy baccatin I by aspergillus niger

The biotransformation of baccatin VI (1) and 1beta-hydroxybaccatin I (2) with the filamentous fungus Aspergillus niger produced four new taxane diterpenoids taxumairol S(1) (3), taxumairol T(1) (4) and taxumairol S (5), taxumairol T (6), respectively. 1beta-Dehydroxybaccatin VI (7) remained unreacted under the same condition.

Non-imidazole heterocyclic histamine H3 receptor antagonists

Continued exploration of the SAR around the lead imidazopyridine histamine H(3) antagonist 1 has led to the discovery of several related series of heterocyclic histamine H(3) antagonists. The synthesis and SAR of indolizine, indole and pyrazolopyridine based compounds are now described.

Synthesis, antiviral activity and pharmacokinetics of P1/P1' substituted 3-aminoindazole cyclic urea HIV protease inhibitors

A series of P1/P1' substituted cyclic urea analogues were prepared in an attempt to increase the intra-cellular antiviral potency of the nonsymmetrical 3-aminoindazoles DMP 850 and DMP 851. The effect of alkyl substitution of the P1/P1' residues on cellular antiviral potency, protein binding, resistance profile and pharmacokinetics are described.

Design, synthesis, and biological activity of novel factor Xa inhibitors: 4-aryloxy substituents of 2,6-diphenoxypyridines

A novel series of triaryloxypyridines have been designed to inhibit factor Xa, a serine protease strategically located in the coagulation cascade. Inhibitor 5e has a K(I) against factor Xa of 0.12nM and is greater than 8000- and 2000-fold selective over two related serine proteases, thrombin and trypsin, respectively. The 4-position of the central pyridine has been identified as a site that tolerates various substitutions without deleterious effects on potency and selectivity. This suggests that the 4-position of the pyridine ring is an ideal site for chemical modifications to identify inhibitors with improved pharmacokinetic characteristics. This investigation has resulted in inhibitor 5d, which has an oral availability of 6% in dogs. The synthesis, in vitro activity, and in vivo profile of this class of inhibitors is outlined.