Effects of acute and chronic attenuation of postprandial hyperglycemia on postglucose-load endothelial function in insulin resistant individuals: is stimulation of first phase insulin secretion beneficial for the endothelial function?

The aim of the study is to determine if attenuation of postprandial hyperglycemia, by acutely and chronically enhancing postprandial insulin secretion in insulin-resistant individuals, improves the endothelial dysfunction. We assessed postoral glucose-load endothelial function in 56 insulin-resistant subjects with the Flow-Mediated-Dilation (FMD) technique. We randomized subjects to intervention/control group, and examined the acute and chronic effect of nateglinide, an oral antidiabetic drug of rapid action. In the intervention group, postoral glucose-load (post-OGL) FMD delta values deteriorated when compared to pre-OGL values, most significantly at 3 h post-OGL, on the following days: on the first study day termed "Baseline day" (p=0.04); on both days after 3 months of nateglinide treatment [with nateglinide administered on study-day "acute+chronic" (p=0.01); and without nateglinide on study-day "Closing day", p=0.001]. Post-OGL changes in the control group were nonsignificant both at Baseline and on Closing day. After a single dose of nateglinide "Acute day", post-OGL FMD deterioration was abolished. There was an increment in post-OGL FMD delta values most significant at 2 h post-OGL (p=0.02). Insulin concentrations increased while glucose concentrations decreased on study-days with nateglinide when compared to study-days without (p=<0.001 for both insulin and glucose). Comparisons for insulin and glucose concentrations between days with nateglinide, and likewise between days without, showed no significant difference. Postglucose load endothelial dysfunction can be prevented by administration of nateglinide, however, after 3 months of nateglinide treatment, this effect is abolished. Chronically increased insulin secretion could counteract the initial beneficial effect of reduced glucose excursions. We found no relationship between postprandial hyperglycemia and post-OGL FMD.

New drugs08, part 2

In this article, you'll learn about eight new drugs, including: doripenem, an antibiotic for complicated intra-abdominal and urinary tract infections. Maraviroc, a new antiretroviral agent to treat HIV infection. Ixabepilone, a new drug for refractory metastatic breast cancer. Unless otherwise specified, the information in the following summaries applies to adults, not children. Consult the package insert for information about each drug's safety during pregnancy and breast-feeding. Also consult a pharmacist, the package insert, or a comprehensive drug reference for more details on precautions, drug interactions, and adverse reactions for all these drugs.

Maraviroc: new drug. Multiple antiretroviral treatment failure: too soon to reach conclusions

(1) The choice of treatment for HIV-infected patients in whom several lines of antiretroviral therapy have failed is particularly difficult. Some antiretroviral drugs (enfuvirtide and some HIV protease inhibitors) remain effective, at least in the short term. (2) Maraviroc is the first CCR5 antagonist to be licensed for use in this setting. It acts by blocking one of the two coreceptors, CCR5, needed for HIV entry into CD4+ lymphocytes. It is approved for use in HIV-infected patients with multiple antiretroviral failure. (3) Two double-blind placebo-controlled trials including 1076 patients infected by HIV strains using only the CCR5 coreceptor tested the effect of adding maraviroc at a dose of 300 mg twice a day to an optimised treatment. After 8 weeks, maraviroc was more effective than placebo in reducing viral load (undetectable in 45.5% versus 16.7% of patients) and in increasing the CD4+ cell count (+124 cells/mm3 versus +61 cells/mm3); both of these differences are statistically significant. (4) After treatment with maraviroc, 50% to 60% of patients harboured viruses that did not exclusively rely on CCR5 for host cell entry. The possible clinical consequences of this change in tropism are unclear. (5) A double-blind trial of maraviroc included 190 patients with multiple antiretroviral failure who were infected by HIV variants not requiring CCR5 for host cell entry; maraviroc was not shown to be effective. (6) Data obtained with other CCR5 antagonists, and preclinical data obtained with maraviroc, point to a possible increase in the risk of hepatitis, infections, cancer, and QT prolongation. More data are also needed concerning the risk of muscle toxicity and ischaemic cardiovascular events. (7) Maraviroc is metabolised by the cytochrome P450 isoenzyme CYP 3A4, hence a high risk of interactions with CYP 3A4 inducers and inhibitors. (8) In practice, given the absence of long-term evaluation, clinical assessment of maraviroc is too limited to recommend the use of this drug outside the clinical trial setting.

FGFR1/PI3K/AKT signaling pathway is a novel target for antiangiogenic effects of the cancer drug fumagillin (TNP-470)

Fibroblast growth factor-1 (FGF1), a prototypic member of the FGF family, is a potent angiogenic factor. Although FGF-stimulated angiogenesis has been extensively studied, the molecular mechanisms regulating FGF1-induced angiogenesis are poorly understood in vivo. Fumagillin, an antiangiogenic fungal metabolite, has the ability to inhibit FGF-stimulated angiogenesis in the chicken chorioallantoic membrane (CAM). In the current study, chicken CAMs were transfected with a signal peptide-containing version of the FGF1 gene construct (sp-FGF1). Transfected CAMs were then analyzed in the presence and absence of fumagillin treatment with respect to the mRNA expression levels and protein activity of the FGF1 receptor protein (FGFR1), phosphatidylinositol 3-kinase (PI3K), and its immediate downstream target, AKT-1 (protein kinase B). Treatment of sp-FGF1-transfected CAMs with fumagillin showed downregulation for both PI3K and AKT-1 proteins in mRNA expression and protein activity. In contrast, no major alterations in FGFR1 mRNA expression level were observed. Similar patterns of mRNA expression for the above three proteins were observed when the CAMs were treated with recombinant FGF1 protein in place of sp-FGF1 gene transfection. Investigation using biotin-labeled fumagillin showed that only the FGF1 receptor protein containing the cytoplasmic domain demonstrated binding to fumagillin. Furthermore, we demonstrated endothelial-specificity of the proposed antiangiogenic signaling cascade using an in vitro system. Based on these findings, we conclude that the binding of fumagillin to the cytoplasmic domain of the FGF1 receptor inhibited FGF1-stimulated angiogenesis both in vitro and in vivo.

[Clinical evaluation of efficacy and safety of nateglinide in the treatment of type 2 diabetes]

OBJECTIVE

To evaluate the efficacy and safety of nateglinide, a new antidiabetic agent, in the treatment of type 2 diabetes.

METHODS

A total of 219 treatment-naïve patients with type 2 diabetes from 6 centers were enrolled in this study and blindly divided into nateglinide group (n = 105) and repaglinide group (n = 114). In all patients, the disease was confirmed for at least three months. The whole observation lasted for 12 weeks. The efficacy indicators measured include glycohemoglobin A1c (HbA1c), fasting blood glucose, and 2 hours postprandial blood glucose, and the safety parameters measured included renal and hepatic function, serum lipids, and blood and urea profiles.

RESULTS

Similar decreases in fasting blood glucose, 2 hours postprandial blood glucose, and HbA1 c were found in both nateglinide group and repaglinide group without significant differences. No severe adverse events were noted. The hypoglycemia event reports were not significantly different between these two groups.

CONCLUSION

Nateglinide is an effective and safe drug in treating type 2 diabetes.

Anti-tumor effect of angiogenesis inhibitor TNP-470 and 5-FU combined therapy on human gastric cancer xenograft

BACKGROUND/AIMS

TNP-470, an angiogenesis inhibitor, has already been used in combination with chemotherapy to enhance its antitumor activity. The mechanism of enhanced antitumor activity in combination therapy has not been clarified, however, and few studies have described the combined effect of TNP-470 and 5-fluorouracil (5-FU) on gastric cancer. The present study was conducted to investigate the effect of TNP-470 + 5-FU on gastric cancer cell line MKN-45 in vivo and in vitro.

METHODOLOGY

MKN-45 cells were subcutaneously injected into mice that were divided into 4 groups: a control group, a 5-FU treated group, a TNP-470 treated group, and a 5-FU + TNP-470 treated group. After the inoculation, the volume of subcutaneous tumors was measured. Blood and lymphatic vessels were also analyzed for the assessment of lymphangiogenesis.

RESULTS

Compared with 5-FU or TNP-470 alone, the combined effect of TNP-470 and 5-FU significantly inhibited and suppressed tumor growth in a synergistic fashion. The combined therapy significantly suppressed both angiogenesis and lymphagenesis.

CONCLUSIONS

The study suggests that the combined therapy provides an enhanced antitumor effect on human gastric cancer. The enhanced antitumor activity is explained mainly by the stronger inhibition of angiogenesis.

Nateglinide prevents fatty liver through up-regulation of lipid oxidation pathway in Goto-Kakizaki rats on a high-fat diet

Dyslipidemia and fatty liver are important components of the metabolic syndrome and are the factors most commonly associated with the development of nonalcoholic fatty liver disease. Delayed and excessive insulin secretion in response to food intake is a key element in the onset of these risk factors. Nateglinide (NAT) is known to restore early-phase insulin secretion. We assessed the effect of NAT on postprandial hypertriglyceridemia and fatty liver in type 2 diabetic Goto-Kakizaki (GK) rats. The GK rats fed a high-fat diet containing 30% beef tallow twice a day were administered either the vehicle alone or NAT (50 mg/kg) before each meal for 12 weeks. Delayed insulin secretion and an increase of total insulin release were caused by feeding 30% beef tallow to the rats. This diet also induced postprandial hypertriglyceridemia and increased the hepatic triglyceride content. Treatment with NAT restored early-phase insulin secretion without any increase of total insulin release and also reduced postprandial hypertriglyceridemia and the hepatic triglyceride content. There was up-regulation of the hepatic expression of peroxisome proliferators-activated receptor alpha and its downstream enzymes after 12 weeks of NAT treatment, as well as normalization of the plasma total ketone body level. Furthermore, NAT also up-regulated hepatic expression of the adiponectin receptor AdipoR2, although there was no effect on the plasma adiponectin level. These findings indicate that long-term treatment with NAT prevented the development of fatty liver through the up-regulation of hepatic lipid oxidation pathways. Restoration of early-phase insulin secretion and suppression of recurrent postprandial hypertriglyceridemia might be involved in these effects of NAT. The present results may support the use of NAT to prevent the onset and progression of the metabolic syndrome and chronic liver disease.

Maraviroc (Celsentri) for multidrug-resistant human immunodeficiency virus (HIV)-1

(1) Maraviroc belongs to a new class of antiretroviral drugs designed to block entry of HIV-1 into CD4+ T-cells via the CCR5 coreceptor. It is indicated for combination therapy in treatment-experienced adults infected with CCR5-tropic HIV-1 that is resistant to multiple antiretroviral agents. (2) Results from two randomized controlled trials (RCTs) indicate that in treatment experienced patients, maraviroc, combined with optimized background therapy (OBT), significantly decreases the level of HIV-1 RNA in the blood (viral load) when compared with OBT alone. The number of patients achieving undetectable viral loads and CD4+ cell count increases were also significantly higher in those receiving maraviroc. (3) Most patients experiencing treatment failure with maraviroc exhibit tropism changes from CCR5-tropic to CXCR4-using virus, but there is no evidence of disease progression. (4) Adverse effects reported with maraviroc include cough, fever, upper respiratory tract infections, rash, muscle and joint pain, abdominal pain, and postural hypotension (dizziness). No significant increases in cardiovascular events, hepatotoxicity, infections or malignancies have been reported with short-term maraviroc therapy. Several post-marketing studies will assess maraviroc's long-term safety for immune function, liver function, malignancy, cardiac events, and risks associated with changes in tropism. (5) Results from an ongoing trial in treatment naive patients suggest that maraviroc may not be superior in terms of viral suppression to standard therapy, but may significantly increase the number of CD4+ T-cells.

Safety of nateglinide as used in general practice in England: results of a prescription-event monitoring study

Nateglinide (Starlix((R))) is licensed for the treatment of Type 2 diabetes in patients inadequately controlled with metformin. The study objective was to monitor the safety and use of nateglinide prescribed by primary care physicians (GPs) in England, using the observational cohort technique, Prescription-Event Monitoring. Exposure data were derived from dispensed nateglinide prescriptions issued October 2001-June 2004; demographic and outcome data, from questionnaires sent to patients' GPs at least 6 months after patients' first prescription. Incidence densities (IDs; number of first reports of an event/1,000 patient-months exposure) were calculated for month 1 (ID(1)), months 2-6 (ID(2-6)); rate differences [ID(1)-ID(2-6) (+99% CI)] were examined. Cohort comprised 4,557 patients, median age 60 (IQR 51, 68 years); 2,439 (53.5%) male; 3,463 (76.0%) received nateglinide in combination with metformin. GPs reported 1,625 reasons for stopping in 1,474 (32.3%) patients and 80 events as adverse drug reactions in 66 (1.5%) patients. Events associated with starting treatment included nausea/vomiting [ID(1)-ID(2-6) 9.6 (99% CI 5.3, 13.9)], malaise/lassitude [ID(1)-ID(2-6) 6.03 (99% CI 2.2, 9.9)]. No serious hypersensitivity reactions were reported. Two pregnancies (< 0.1%) and 73 deaths (1.6%) were reported. Nateglinide appeared to be generally well tolerated when used in combination with metformin for the treatment of Type 2 diabetes.

Potential utility of combination therapy with nateglinide and telmisartan for metabolic derangements in Zucker Fatty rats

The metabolic syndrome is strongly associated with insulin resistance and has been recognized as a cluster of risk factors for cardiovascular disease. Insulin resistance and/or impaired early-phase insulin secretion are major determinants of postprandial hyperglycemia. In this study, we investigated the potential utility of combination therapy with telmisartan, an angiotensin II receptor blocker and nateglinide, a rapid-onset/short-duration insulinotropic agent, for the treatment of postprandial hyperglycemia and metabolic derangements in Zucker Fatty (ZF) rats. ZF rats fed twice daily were given vehicle, 50 mg/kg of nateglinide, 5 mg/kg of telmisartan, or both for 6 weeks. Combination therapy with nateglinide and telmisartan for 2 weeks ameliorated postprandial hyperglycemia in ZF rats fed twice daily. Furthermore, 6-week treatment with nateglinide and telmisartan not only decreased fasting plasma insulin, triglycerides, and free fatty acid levels, but also improved the responses of blood glucose to insulin and subsequently reduced the decremental glucose areas under the curve in the ZF rats. Combination therapy also restored the decrease of plasma adiponectin levels in the ZF rats. Monotherapy with nateglinide or telmisartan alone didnot significantly improve these metabolic parameters. These observations demonstrate that combination therapy with nateglinide and telmisartan may improve the metabolic derangements by ameliorating early phase of insulin secretion as well as insulin resistance in ZF rats fed twice daily. Our present findings suggest that the combination therapy with nateglinide and telmisartan could be a promising therapeutic strategy for the treatment of the metabolic syndrome.

CCR5 antagonists in the treatment of treatment-naive patients infected with CCR5 tropic HIV-1

A new class of antiretroviral drugs is now available to the HIV provider: The CCR5 Antagonists belong to a group of entry inhibitors with a novel mechanism of action. While these antagonists do not directly interfere with any of the steps of HIV replication, they block the CCR5 receptor, one of the co-receptors HIV uses to enter its target cell. Thus CCR5 antagonists are able to prevent infection of the cell and represent a new and unique mechanism for the treatment of HIV. There is great interest in utilizing this new drug class in early treatment of HIV to prevent infection of large cell pools; CCR5 antagonists even may be useful tools in the various settings of exposure prophylaxis. Maraviroc is now approved in both the European Union and the United States for the treatment of HIV infection. This is the first medication belonging to the new class of CCR5 antagonists, and the first approval of an orally available drug in a new class since 1996. Aplaviroc, maraviroc, and vicriviroc are small molecule inhibitors of CCR5 that block HIV-1 infection in vitro and reduce plasma HIV-1 RNA in HIV infected subjects by approximately 1.5 log10 copies/mL over 10-14 days when given as single agents. Very limited data is available on the use of CCR5 antagonists in treatment naive patients due to early termination of many trials because of inferior performance or toxicity and at the time of this writing in August 2007 there is only one ongoing non-inferiority trial in the naive patient population. The 48 week interim results of this trial using twice daily maraviroc were reported at the International AIDS Society meeting in July 2007. Maraviroc compared to efavirenz was non-inferior in regards to percentage of subjects reaching viral loads below 400 copies/mL, but not so for the analysis of subjects reaching viral loads below 50 copies/mL. On the other hand maraviroc had a superior side-effect profile, fewer adverse events and a greater increase of CD4 cell count than efavirenz. These data will revitalize the interest in CCR5 antagonists as a treatment option for the treatment-naive patients. In order to be used as first line drugs, CCR5 antagonists face a number of challenges: They will have to be proven to be as potent, durable, safe, and convenient as current available options. Important questions unique to this new class will have to be answered: What are the mechanisms and risks of tropism change? What is the role and needed frequency of tropism testing, and what efficacy is seen in patients with dual-tropic/mixed infection in the long term? Clearly until we have answers to these questions CCR5 antagonists should be reserved for the treatment-experienced patient population with limited treatment options.

CCR5 antagonists: comparison of efficacy, side effects, pharmacokinetics and interactions--review of the literature

In the context of emerging resistance to antiretroviral agents in HIV medicine, the development of new drugs classes with a novel mechanism of action remains essential. The CCR5 co-receptor antagonists inhibit fusion of HIV with the host cell by blocking the interaction between the gp-120 viral glycoprotein and the CCR5 chemokine receptor. So far, four CCR5 antagonists have entered clinical evaluation, of which three are currently still in different stages of clinical assessment. In this review we compare the clinical efficacy in phase I and II as well as the long-term tolerability, pharmacokinetics and interactions of these new antiretroviral drugs entering HIV practice. Being the first CCR5 antagonist to be investigated in clinical trials, aplaviroc showed initial potent antiviral activity. However, after the occurrence of severe hepatotoxicity in several patients, its development had to be stopped in October 2005. The second CCR5 antagonist, maraviroc, has displayed promising results in phase I, II and III studies, showing a significantly greater decline in HIV RNA and CD4 cell increase compared to placebo, with no clinically relevant differences in safety profile and tolerability. The expanded access program for maraviroc was opened in June 2007 in several European countries. The FDA approved the use of maraviroc for antiretroviral therapy of HIV on the 7th of august, 2007. Finally, the third CCR5 antagonist vicriviroc also showed long-term potent viral activity in phase II studies as long as it was boosted with low-dose ritonavir, with no significant differences in grade 3 and grade 4 adverse effects compared to placebo. The phase II clinical trial amongst ART experienced individuals who received Ritonavir-boosted vicriviroc 10-15 mg qd was unblinded early because of the unexpected occurrence of malignant lymphoma and adenoma. However, no further malignancies occurred in the extended follow-up evaluation of this drug until today. Vicriviroc is currently entering phase III evaluation. Pharmacokinetics of maraviroc and vicriviroc may be influenced by coadministration of CYP3A4-inhibitors and -inducers, since both substances are metabolised primarily by the CYP3A4 system. This requires dose adjustments when combined with for instance protease inhibitors (with the exception of tipranavir/r), efavirenz, ketoconazole or rifampin. Concerns have risen about possible class-specific long-term adverse effects of CCR5 antagonists, particularly with regard to hepatotoxicity or malignancy. The pooled data from phase II and III however, so far show no new or added toxicity risk for maraviroc or vicriviroc compared to the respective placebo arms of the trials. Extended follow-up of the vicriviroc trials showed no further case of malignancy, reassuring the overall good tolerability profile of the drug so far.

Treatment with CCR5 antagonists: which patient may have a benefit?

The concept of CCR5 antagonists introduces an additional molecular target. Maraviroc (MVR) is approved by the FDA for use in HIV-1 infected patients for combination antiretroviral treatment of adults infected with only CCR5-tropic HIV-1 who have evidence of viral replication and HIV-1 strains resistant to multiple antiretroviral agents. Tropism and treatment history should guide the use of MVR. Data from clinical trials show significant efficacy of MVR for patients with pre-treatment and multiple class failure. Additional clinical data show a CD4 reconstitution that is more pronounced than with comparator in treatment naive and in late stage patients even without CCR5-tropic virus indicating patients in earlier stages and even patients without CCR5 testing will benefit from MVR. MVR is not licensed for treatment naive patients but it has a high potential for further development in this patient group. It shows better immunological reconstitution than efavirenz. Pooled safety data from all available trials shows good short term tolerability. Caution is needed in hepatitis co-infection with pre-existing liver damage and in patients with heart failure. Isolates from different geographic regions differ in coreceptor usage. Summarizing knowledge on HIV-1 subtypes and CCR5 tropism shows that in principle all subtypes are susceptible to MVR. However, in subtypes A and D dualtropic and alternative coreceptor use were found. Clinical efficacy in patients from regions with A and D predominance should be studied in future trials. In conclusion, MVR will be of benefit for patients in various treatment situations and regions.

How will CCR5 antagonists influence the recommendations for the antiretroviral treatment of HIV-1 infection

The new antiviral CCR5 antagonists have proven to be highly efficient in treatment experienced patient populations with multiple drug failure. Maraviroc is the most advanced compound in clinical development representing this new class of entry inhibitors. The favourable toxicity-, resistance- and pharmacokinetic profile of the drug has been proven in phase III trials in treatment naive and experienced patients. In the latter population, maraviroc had superior antiviral efficacy and immunological activity compared to OBT+placebo alone in the control group. The antiviral responses after 48 weeks were comparable to results obtained from phase III trials with raltegravir and other previous salvage regimens including, darunavir, tipranavir and enfuvirtide. Due to its unique mode of action with exclusive activity against CCR5 tropic strains, viral tropism testing will be mandatory before using CCR5 antagonists in the clinic. The corresponding tests are established and will be further validated. Results from clinical trials indicate that approximately half of the treatment experienced patients will predominantly harbour CCR5 tropic quasispecies and will thus qualify for treatment with CCR5 antagonists. In treatment naive patients maraviroc so far formally failed to prove its non-inferiority to a standard regimen consisting of AZT/3TC+efavirenz after 48 weeks. However, further 96 weeks data will be analysed from this study as well as antiviral efficacy in distinct patient subpopulations. Therefore, it is likely that maraviroc will be recommended in early stages of salvage therapy at present and might replace more inconvenient drugs like enfuvirtide in later lines of therapy. The drug class has also the potential to enter first line therapy but this has to be proven in future trials. Special patient populations like primary HIV infection (PHI), pre- and post exposure prophylaxis, co-infection with tuberculosis and hepatitis B may show special clinical benefit but this is also awaiting confirmation from prospective trials.

CCR5 antagonists in the treatment of treatment-experienced patients infected with CCR5 tropic HIV-1

CCR5 antagonists are a newly developed class of antiretroviral drugs which inhibit viral entry into the host cell by binding to the predominant HIV coreceptor. Data on the use of these new drugs in treatment-experienced HIV patients are emerging. Clinical trials on maraviroc and vicriviroc in pretreated patients recruited more than 1300 individuals. Interim results of these studies indicate that pretreated patients infected with CCR5-tropic viruses benefit from their use in optimized combination regimens. Maraviroc reduces the HIV-1 viral load in patients with previous triple-class failure by 1.96 log10 copies/ml versus 0.99 log10 copies/ml in placebo; vicriviroc shows potency by dose depending viral decrease of 1.51-1.68 log10 copies/ml compared to 0.29 log10 in placebo. As expected, CCR5 antagonists do not reduce viral load in patients harbouring CXCR4-tropic or dual/mixed tropic viruses. Nevertheless, since a considerable percentage of late-stage HIV patients still bear CCR5-tropic viruses, the use of CCR5 antagonists appears promising in properly selected treatment-experienced patients.