Dosing-time dependent testicular toxicity of everolimus in mice

The circadian timing system controls many biological functions in mammals including drug metabolism and detoxification, cell cycle events, and thus may affect pharmacokinetics, target organ toxicity and efficacy of medicines. Selective mTOR (mammalian target of rapamycin) inhibitor everolimus is an immunosuppressant and anticancer drug that is effective against several cancers. The aim of this study was to investigate dosing-time dependent testicular toxicity of subacute everolimus administration in mice. C57BL/6 J male mice were synchronized with Light-Dark (12h:12 h) cycle, with Light-onset at Zeitgeber Time (ZT)-0. Everolimus (5 mg/kg/day) was administered orally to mice at ZT1_rest-span or ZT13_{activity-span} for 4 weeks. Body weight loss, clinical signs, changes in testicular weights, testis histology, spermatogenesis and proliferative activity of germinal epithelium of seminiferous tubules were examined. Steady-state everolimus concentrations in testes were determined with validated HPLC method. Everolimus toxicity was less severe following dosing at ZT13 compared to ZT1, as shown with least body weight loss (p<0.001), least reductions in testes weights (p<0.001) and least histopathological findings. Everolimus-induced histological changes on testes included vacuolisation and atrophy of germinal epithelium, and loss of germinal cell attachment. The severity of everolimus-induced histological toxicity on testes was significantly more evident in mice treated at ZT1 than ZT13 (p<0.001). Spermatogenic cell population significantly decreased when everolimus administered at ZT1 compared to ZT13 (p<0.001). Proliferative activity of germinal epithelium was significantly decreased due to treatment at ZT1 compared to ZT13 (p<0.001). Everolimus concentrations in testes indicated a pronounced circadian variation, which was greater in mice treated at ZT1 compared to ZT13 (p<0.05). Our study revealed dosing-time dependent testicular toxicity of everolimus in mice, which was greater in severity when everolimus administered at early rest-span (daytime-ZT1) than early activity-span (nighttime-ZT13). These findings support the concept of everolimus chronotherapy for minimizing reproductive toxicity and increasing the tolerability of everolimus, as a clinical advantage.

Diurnal expression of MRP4 in bone marrow cells underlies the dosing-time dependent changes in the oxaliplatin-induced myelotoxicity

The expression and function of some xenobiotic transporters varies according to the time of day, causing the dosing time-dependent changes in drug disposition and toxicity. Multidrug resistance-associated protein-4 (MRP4), an ATP­binding cassette (ABC) efflux transporter encoded by the Abcc4 gene, is highly expressed in bone marrow cells (BMCs) and protects them against xenobiotics, including chemotherapeutic drugs. In this study, we demonstrated that MRP4 was responsible for the extrusion of oxaliplatin (L-OHP), a platinum (Pt)-based chemotherapeutic drug, from BMCs of mice, and that the efflux transporter expression exhibited significant diurnal variation. Therefore, we investigated the relevance of the diurnal expression of MRP4 in BMCs for L-OHP-induced myelotoxicity in mice maintained under standardized light/dark cycle conditions. After intravenous injection of L-OHP, the Pt content in BMCs varied according to the injection time. Lower Pt accumulation in BMCs was detected in mice after injection of L-OHP at the mid-dark phase, during which the expression levels of MRP4 increased. Consistent with these observations, the myelotoxic effects of L-OHP were attenuated when mice were injected with L-OHP during the dark phase. This dosing schedule also alleviated the L-OHP-induced reduction of the peripheral white blood cell count. The present results suggest that the myelotoxicity of L-OHP is attenuated by optimizing the dosing schedule. Diurnal expression of MRP4 in BMCs is associated with the dosing time-dependent changes in L-OHP-induced myelotoxicity.

Changing the enzalutamide form from a capsule to a tablet improves the adherence of medicine intake: A case of a significant decrease in the prostate‐specific antigen level and improvement in radiographic findings

Introduction

In June 2018, enzalutamide began to be sold in a tablet form in Japan and Germany. We herein report the case of an improvement in prostate cancer progression due to changing enzalutamide dosage form from a capsule to a tablet.

Case presentation

A 76‐year‐old man was initially referred to our hospital for the further examination of his elevated prostate‐specific antigen level (3664.0 ng/mL). He had developed castration‐resistant prostate cancer 10 months after initial treatment. Treatment with enzalutamide (capsule form) was subsequently initiated. In June 2018, drug form of enzalutamide was changed from a capsule to a tablet. After switching to an enzalutamide tablet, his prostate‐specific antigen level decreased significantly from 493.0 to 26.5 ng/mL.

Conclusion

While the reason for this prostate‐specific antigen response is unclear, changing the enzalutamide form from a capsule to a tablet may have improved the adherence of drug intake and thereby resulted in castration‐resistant prostate cancer control.

Molecular Aspects of Circadian Pharmacology and Relevance for Cancer Chronotherapy

The circadian timing system (CTS) controls various biological functions in mammals including xenobiotic metabolism and detoxification, immune functions, cell cycle events, apoptosis and angiogenesis. Although the importance of the CTS is well known in the pharmacology of drugs, it is less appreciated at the clinical level. Genome-wide studies highlighted that the majority of drug target genes are controlled by CTS. This suggests that chronotherapeutic approaches should be taken for many drugs to enhance their effectiveness. Currently chronotherapeutic approaches are successfully applied in the treatment of different types of cancers. The chronotherapy approach has improved the tolerability and antitumor efficacy of anticancer drugs both in experimental animals and in cancer patients. Thus, chronobiological studies have been of importance in determining the most appropriate time of administration of anticancer agents to minimize their side effects or toxicity and enhance treatment efficacy, so as to optimize the therapeutic ratio. This review focuses on the underlying mechanisms of the circadian pharmacology i.e., chronopharmacokinetics and chronopharmacodynamics of anticancer agents with the molecular aspects, and provides an overview of chronotherapy in cancer and some of the recent advances in the development of chronopharmaceutics.

The Targeted SMAC Mimetic SW IV-134 is a strong enhancer of standard chemotherapy in pancreatic cancer

Background

Pancreatic cancer is a lethal malignancy that frequently acquires resistance to conventional chemotherapies often associated with overexpression of inhibitors of apoptosis proteins (IAPs). We have recently described a novel means to deliver second mitochondria-derived activator of caspases (SMAC) mimetics selectively to cancer cells employing the sigma-2 ligand/receptor interaction. The intrinsic death pathway agonist SMAC offers an excellent opportunity to counteract the anti-apoptotic activity of IAPs. SMAC mimetics have been used to sensitize several cancer types to chemotherapeutic agents but cancer-selective delivery and appropriate cellular localization have not yet been considered. In our current study, we tested the ability of the sigma-2/SMAC drug conjugate SW IV-134 to sensitize pancreatic cancer cells to gemcitabine.

Methods

Using the targeted SMAC mimetic SW IV-134, inhibition of the X-linked inhibitor of apoptosis proteins (XIAP) was induced pharmacologically and its impact on cell viability was studied alone and in combination with gemcitabine. Pathway analyses were performed by assessing caspase activation, PARP cleavage and membrane blebbing (Annexin-V), key components of apoptotic cell death. Single-agent treatment regimens were compared with combination therapy in a preclinical mouse model of pancreatic cancer.

Results

The sensitizing effect of XIAP interference toward gemcitabine was confirmed via pharmacological intervention using our recently designed, targeted SMAC mimetic SW IV-134 across a wide range of commonly used pancreatic cancer cell lines at concentrations where the individual drugs showed only minimal activity. On a mechanistic level, we identified involvement of key components of the apoptosis machinery during cell death execution. Furthermore, combination therapy proved superior in decreasing the tumor burden and extending the lives of the animals in a preclinical mouse model of pancreatic cancer.

Conclusion

We believe that the strong sensitizing capacity of SW IV-134 in combination with clinically relevant doses of gemcitabine represents a promising treatment option that warrants clinical evaluation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0470-4) contains supplementary material, which is available to authorized users.

Molecular Targets for Small-Molecule Modulators of Circadian Clocks

BACKGROUND

Circadian clocks are endogenous timing systems that regulate various aspects of mammalian metabolism, physiology and behavior. Traditional chronotherapy refers to the administration of drugs in a defined circadian time window to achieve optimal pharmacokinetic and therapeutic efficacies. In recent years, substantial efforts have been dedicated to developing novel small-molecule modulators of circadian clocks.

METHODS

Here, we review the recent progress in the identification of molecular targets of small-molecule clock modulators and their efficacies in clock-related disorders. Specifically, we examine the clock components and regulatory factors as possible molecular targets of small molecules, and we review several key clock-related disorders as promising venues for testing the preventive/therapeutic efficacies of these small molecules. Finally, we also discuss circadian regulation of drug metabolism.

RESULTS

Small molecules can modulate the period, phase and/or amplitude of the circadian cycle. Core clock proteins, nuclear hormone receptors, and clock-related kinases and other epigenetic regulators are promising molecular targets for small molecules. Through these targets small molecules exert protective effects against clock-related disorders including the metabolic syndrome, immune disorders, sleep disorders and cancer. Small molecules can also modulate circadian drug metabolism and response to existing therapeutics.

CONCLUSION

Small-molecule clock modulators target clock components or diverse cellular pathways that functionally impinge upon the clock. Target identification of new small-molecule modulators will deepen our understanding of key regulatory nodes in the circadian network. Studies of clock modulators will facilitate their therapeutic applications, alone or in combination, for clock-related diseases.

Circadian rhythmicity, variability and correlation of interleukin-6 levels in plasma and cerebrospinal fluid of healthy men

BACKGROUND

Interleukin-6 (IL-6) is a cytokine with pleiotropic actions in both the periphery of the body and the central nervous system (CNS). Altered IL-6 secretion has been associated with inflammatory dysregulation and several adverse health consequences. However, little is known about the physiological circadian characteristics and dynamic inter-correlation between circulating and CNS IL-6 levels in humans, or their significance.

METHODS

Simultaneous assessment of plasma and cerebrospinal fluid (CSF) IL-6 levels was performed hourly in 11 healthy male volunteers over 24h, to characterize physiological IL-6 secretion levels in both compartments.

RESULTS

IL-6 levels showed considerable within- and between-subject variability in both plasma and CSF, with plasma/CSF ratios revealing consistently higher levels in the CSF. Both CSF and plasma IL-6 levels showed a distinctive circadian variation, with CSF IL-6 levels exhibiting a main 24h, and plasma a biphasic 12h, circadian component. Plasma peaks were roughly at 4 p.m. and 4 a.m., while the CSF peak was at around 7 p.m. There was no correlation between coincident CSF and plasma IL-6 values, but evidence for significant correlations at a negative 7-8h time lag.

CONCLUSIONS

This study provides evidence in humans for a circadian IL-6 rhythm in CSF and confirms prior observations reporting a plasma biphasic circadian pattern. Our results indicate differential IL-6 regulation across the two compartments and are consistent with local production of IL-6 in the CNS. Possible physiological significance is discussed and implications for further research are highlighted.

SL-01, an oral derivative of gemcitabine, inhibited human breast cancer growth through induction of apoptosis

SL-01 is an oral derivative of gemcitabine that was synthesized by introducing the moiety of 3-(dodecyloxycarbonyl) pyrazine-2-carbonyl at N4-position on cytidine ring of gemcitabine. We aimed to evaluate the efficacy of SL-01 on human breast cancer growth. SL-01 significantly inhibited MCF-7 proliferation as estimated by colorimetric assay. Flow cytometry assay indicated the apoptotic induction and cell cycle arrest in G1 phase. SL-01 modulated the expressions of p-ATM, p53 and p21 and decrease of cyclin D1 in MCF-7 cells. Further experiments were performed in a MCF-7 xenografts mouse model. SL-01 by oral administration strongly inhibited MCF-7 xenografts growth. This effect of SL-01 might arise from its roles in the induction of apoptosis. Immunohistochemistry assay showed the increase of TUNEL staining cells. Western blotting indicated the modulation of apoptotic proteins in SL-01-treated xenografts. During the course of study, there was no evidence of toxicity to mice. In contrast, the decrease of neutrophil cells in peripheral and increase of AST and ALT levels in serum were observed in the gemcitabine-treated mice.

CONCLUSION

SL-01 possessed similar activity against human breast cancer growth with gemcitabine, whereas, with lower toxicity to gemcitabine. SL-01 is a potent oral agent that may supplant the use of gemcitabine.

Pharmacokinetics and metabolism of SL-01, a prodrug of gemcitabine, in rats

PURPOSE

SL-01, dodecyl-3-((1-((2R,4R,5R)-3,3-difluoro-4-hydroxy-5-(hydroxymethyl)-tetrahydrofuran-2-yl)-2-oxo-1,2-dihydropyrimidin-4-yl) carbamoyl) pyrazine-2-carboxylate, is a prodrug of gemcitabine. Our previous reports suggested that SL-01 possesses superior bioavailability and anticancer activity to gemcitabine in mice. In this study, its pharmacokinetics and metabolisms were investigated in rats.

METHODS

The pharmacokinetics of SL-01 was studied following intravenous or oral administration of SL-01 to Sprague-Dawley rats. The metabolites profile of SL-01 was further determined in rats receiving intravenous administration of SL-01. Blood samples were analyzed by using LC-MS or LC-MS/MS assay.

RESULTS

Following administration with SL-01 intravenously or orally, SL-01, plasma gemcitabine released from SL-01 as well as the sum of gemcitabine (gemcitabine converted from SL-01 and plasma gemcitabine) exhibited higher values of V z /F and CL z /F, and longer MRT and t 1/2 than those of gemcitabine administered intravenously. The C max of gemcitabine produced by intravenous SL-01 was higher than that of gemcitabine dosed intravenously. The absolute bioavailability for the sum of gemcitabine was 32.2 % for intravenous and 22.2 % for oral administration with SL-01, respectively. After a single intravenous administration, a total of 5 components (M1, M2, M3, M4, and M5) were detected and identified as the metabolites of SL-01 in the plasma of rats. M1 and M2 were formed from the methylation and reduction of SL-01, respectively. Hydrolysis of the amide bond of SL-01 gave M3 and M4. M5 was produced from further dealkylation of M3.

CONCLUSIONS

SL-01 displayed improved absorption, good distribution, high clearance, long mean residence time, and moderate bioavailability after administered intravenously or orally to rats. The major metabolic pathways of SL-01 involved methylation, reduction, hydrolysis, and dealkylation. These results suggested that SL-01 acts as a prodrug of gemcitabine in rats.

The mammalian clock and chronopharmacology

Increases in our understanding of the molecular control of circadian rhythms and subsequent signaling pathways has allowed for new therapeutic drug targets to be identified as well as for a better understanding of how to more efficaciously and safely utilize current drugs. Here, we review recent advances in targeting components of the molecular clock in mammals for the development of novel therapeutics as well as describe the impact of the circadian rhythm on drug efficacy and toxicity.

Everolimus enhances gemcitabine-induced cytotoxicity in bladder-cancer cell lines

The purpose of this study was to determine whether everolimus, a rapamycin derivative, might significantly enhance the cytotoxicity of gemcitabine, an antitumor drug, in two human bladder-cancer cell lines. Human bladder-cancer T24 and 5637 cells were incubated with gemcitabine and everolimus in a range of concentrations either alone or in combination for 72 h. Flow cytometry, comet assay, MTT method and optical microscopy were used to assess cell proliferation, cell cycle, DNA damage, and morphological alterations. Gemcitabine exerted an inhibitory effect on T24 and 5637 cell proliferation, in a concentration-dependent manner. Everolimus significantly reduced proliferation of 5637 bladder cancer cells (IC₃₀) at 1 μM), whereas T24 demonstrated marked resistance to everolimus treatment. A significant antiproliferative effect was obtained combining gemcitabine (100 nM) with everolimus (0.05-2 μM) with an arrest of cell cycle at S phase. Furthermore, an increase in frequency of DNA damage, apoptotic bodies, and apoptotic cells was observed when T24 and 5637 cancer cells were treated simultaneously with both drugs. Data show that in vitro combination produced a more potent antiproliferative effect when compared with single drugs.