Canagliflozin improves glycaemic control over 28 days in subjects with type 2 diabetes not optimally controlled on insulin.

AIM: Canagliflozin is a sodium-glucose co-transporter 2 (SGLT2) inhibitor that is being investigated for the treatment of type 2 diabetes mellitus (T2DM). METHODS: This was a randomized, double-blind, placebo-controlled, parallel-group, 28-day study conducted at two sites, in 29 subjects with T2DM not optimally controlled on insulin and up to one oral antihyperglycaemic agent. Subjects were treated with canagliflozin 100 mg QD or 300 mg twice daily (BID) or placebo. Safety, tolerability, pharmacokinetic characteristics and pharmacodynamic effects of canagliflozin were examined. Glucose malabsorption following a 75-g oral glucose challenge was also examined. RESULTS: Canagliflozin pharmacokinetics were dose-dependent, and the elimination half-life ranged from 12 to 15 h. After 28 days, the renal threshold for glucose excretion was reduced; urinary glucose excretion was increased; and A1C, fasting plasma glucose and body weight decreased in subjects administered canagliflozin (A1C reductions: 0.19% with placebo, 0.73% with 100 mg QD, 0.92% with 300 mg BID; body weight changes: 0.03 kg increase with placebo, 0.73 kg reduction with 100 mg QD, 1.19 kg reduction with 300 mg BID). Glucose malabsorption was not observed with canagliflozin treatment. There were no deaths, serious adverse events or severe hypoglycaemic episodes. The incidence of adverse events was similar across groups. There were no clinically meaningful changes in routine laboratory safety tests, vital signs or electrocardiograms. CONCLUSION: In subjects receiving insulin and oral antihyperglycaemic therapy, canagliflozin was well tolerated without evidence for glucose malabsorption, had pharmacokinetic characteristics consistent with once-daily dosing, and improved glycaemic control.

Canagliflozin, a novel inhibitor of sodium glucose co-transporter 2, dose dependently reduces calculated renal threshold for glucose excretion and increases urinary glucose excretion in healthy subjects.

Canagliflozin, a potent, selective sodium glucose co-transporter 2 inhibitor in development for treatment of type 2 diabetes, lowers plasma glucose (PG) by lowering the renal threshold for glucose (RT(G) ) and increasing urinary glucose excretion (UGE). An ascending single oral-dose phase 1 study investigated safety, tolerability and pharmacodynamics of canagliflozin in healthy men (N = 63) randomized to receive canagliflozin (n = 48) or placebo (n = 15). Canagliflozin (10, 30, 100, 200, 400, 600 or 800 mg q.d. or 400 mg b.i.d.) was administered to eight cohorts (six subjects/cohort: canagliflozin; two subjects/cohort: placebo). Dose dependently, canagliflozin decreased calculated 24-h mean RT(G) with maximal reduction to approximately 60 mg/dl, and increased mean 24-h UGE. At doses >200 mg administered before breakfast, canagliflozin reduced postprandial PG and serum insulin excursions at that meal. Canagliflozin was generally well tolerated; most adverse events were mild and no hypoglycaemia was reported. These results support further study of canagliflozin.

Importance of early phase insulin secretion to intravenous glucose tolerance in subjects with type 2 diabetes mellitus.

Insulin secretion is impaired in type 2 diabetes with the early response being essentially absent. The loss of this early insulin secretion is hypothesized to be important in the deterioration of glucose tolerance. To determine whether enhancement of the early-phase insulin response can enhance glucose tolerance, we administered 1) 120 mg nateglinide, an insulinotropic agent that enhances early insulin secretion; 2) 10 mg glyburide, which enhances the later phases of insulin secretion; or 3) placebo in random order to 21 subjects with type 2 diabetes (14 males and 7 females; aged 59.2 +/- 2.1 yr, x +/- SEM; body mass index 29.7 +/- 1.0 kg/m(2); fasting plasma glucose 8.1 +/- 0.1 mM). beta-Cell function was quantified as the incremental area under the curve for different time periods for the 5 h following iv glucose administration and glucose tolerance as the glucose disappearance constant (Kg) from 10 to 60 min. Insulin release commenced immediately after nateglinide administration, even before glucose injection, but this was not observed with glyburide. Both nateglinide and glyburide enhanced glucose-induced insulin release, compared with placebo (area under the curve -15-300 min: nateglinide 23,595 +/- 11,212 pM/min, glyburide 54,556 +/- 15,253 pM/min, placebo 10,242 +/- 2,414 pM/min). The profiles of insulin release demonstrated significant enhancement of release between -15 and 30 min for nateglinide, compared with glyburide and between 60 and 300 min for glyburide over nateglinide. Kg increased by 15% with nateglinide (0.87 +/- 0.04%/min), but it did not increase significantly with glyburide (0.79 +/- 0.04%/min), compared with placebo (0.76 +/- 0.04%/min). The enhancement of insulin release by glyburide resulted in a lower minimal glucose concentration with glyburide (3.8 +/- 0.2 mM), compared with nateglinide (5.0 +/- 0.2 mM) and placebo (5.9 +/- 0.2 mM). Thus, enhancement of the early phase of insulin secretion improves iv glucose tolerance, whereas delaying it by 30 min results in a slower rate of glucose disappearance for the first 2 h after iv glucose administration. Further, the differences in the kinetics of nateglinide and glyburide action results in continued insulin release with glyburide despite the fact that glucose levels have returned to basal, thus resulting in a further reduction in glucose levels and a lower nadir.

Uptake of temozolomide in a rat glioma model in the presence and absence of the angiogenesis inhibitor TNP-470.

The angiogenic phenotype is associated with hyperpermeable capillaries. Through treatment with angiogenesis inhibitors capillary permeability may be reduced, and it can be anticipated that cytotoxic agents coadministered may be adversely affected. The current investigation examined this possibility for the combination of TNP-470, an angiogenesis inhibitor, and temozolomide (TMZ), a DNA-alkylating agent with demonstrated activity in brain tumors. TNP-470 (30 mg/kg) was given s.c. on days 6, 8, 10, 12, and 14 following s.c. implantation of rat C6 glioma cells in Sprague-Dawley rats. On the 15th day following tumor implantation, control (no TNP-470) and treated rats received 40 mg/kg of TMZ intraarterially. Prior to dosing, a linear microdialysis probe was placed in the tumor to collect interstitial fluid. Plasma and interstitial fluid samples were collected for 8 h and measured for TMZ by a high-performance liquid chromatography assay. Pharmacokinetic parameters for TMZ were calculated by noncompartmental methods. Total systemic clearance (39.8 +/- 7 versus 44.2 +/- 14 ml min(-1) kg(-1)) and volume of distribution (5.4 +/- 2 versus 5.2 +/- 0.8 L kg(-1)) were not significantly different in control and TNP-470-treated animals. However, the mean TMZ area under the interstitial fluid concentration-time curve was reduced by 25% in the TNP-470-treated group compared to the control (5450 +/- 1892 versus 4120 +/- 1790 micrograms min ml(-1); P < 0.05). It appears that TNP-470 caused this reduction in the tumor uptake of TMZ by its pharmacodynamic action on the tumor vasculature. Since combination regimens using angiogenesis inhibitors and cytotoxic drugs will be needed to determine how such combinations can be used effectively. The current animal model, which utilized tumor microdialysis, can serve as a model to further analyze combination chemotherapy.

In vivo microdialysis to characterize drug transport in brain tumors: analysis of methotrexate uptake in rat glioma-2 (RG-2)-bearing rats.

Brain microdialysis was applied to sample free methotrexate (MTX) concentrations in brain extracellular fluid of normal and RG-2 glioma-bearing rats. All animals received 50 mg/kg of MTX intra-arterially following which serial blood and interstitial fluid samples were collected for 3 h and measured for MTX by an HPLC assay. Retrodialysis was used to estimate the in vivo recovery of MTX from brain. A linear two-compartment model was fitted to the plasma MTX concentration-time data in both the normal and RG-2 groups. The mean total body clearance and volume of distribution at steady state of MTX varied from 0.90 +/- 0.3 to 0.24 +/- 0.02 l h-1 kg-1 (P < 0.05) and from 0.58 +/- 0.24 to 0.21 +/- 0.16 l kg-1 (P < 0.05) in control and tumor rats, respectively. The significant reductions in clearance and volume of distribution at steady-state were attributed in part to a cachectic state in the RG-2 animals in which total body water was reduced. The mean MTX area under the interstitial fluid concentration-time curve (AUC) was 171.6 +/- 69.14 micrograms min ml-1(control) and 583.5 +/- 296.7 micrograms min ml-1 (brain tumor-bearing rats). The significantly higher AUC values obtained with RG-2 rats compared with control rats may have resulted from high plasma MTX concentrations and a more permeable blood-tumor barrier (BTB). A hybrid physiologically based pharmacokinetic model was used to characterize the mechanisms responsible for the high MTX brain tumor concentrations. In conclusion, a microdialysis technique was successfully utilized to examine the extracellular uptake of MTX in brain. This technique can be a powerful tool to evaluate intracerebral drug kinetics and the delivery of drugs to brain tumors.

Zalcitabine. Clinical pharmacokinetics and efficacy.

Zalcitabine (ddC) was the first drug to be approved under the US Food and Drug Administration's (FDA's) accelerated drug approval process. Zalcitabine is a potent nucleoside analogue inhibitor of reverse transcriptase used in the treatment of HIV infection. It is approximately 10-fold more potent than zidovudine (AZT) on a molar basis in vitro. Zalcitabine is well absorbed orally and reaches maximal plasma concentrations within 1 to 2 hours. In humans it is mainly eliminated by renal excretion of unchanged drug, and patients with renal failure may exhibit a prolonged half-life. A variety of clinical trials have evaluated the efficacy of zalcitabine based on improved survival and decreased frequency of opportunistic infections and on a surrogate marker of HIV disease, the CD4 count, or the concentration of an antigen associated with HIV, p24. Alternating zalcitabine therapy with zidovudine therapy was associated with increased CD4+ lymphocyte counts and reduced plasma p24 antigen levels. Zalcitabine can cause peripheral neuropathy (in 17 to 31% of patients), which is dose-related and is completely reversible when the drug is discontinued. Zalcitabine will continue to play a role in chemotherapeutic approaches to HIV.

Preparation and in vitro evaluation of magnetic microsphere-methotrexate conjugate drug delivery systems.

Magnetic microsphere-methoxtrexate (MM-MTX) conjugates prepared by several different methods were analyzed for their suitability for in vivo use. MM-MTX were prepared by the following methods: (A) reaction of MTX with poly(ethylene glycol) 1500 (PEG) to form a poly(ethylene glycol)-methotrexate conjugate (PEGMTX) which was then added to a ferrous/ferric ion salt solution to give MM-MTX I; (B) reaction of ferrous/ferric ion salts with PEG to give a ferromagnetic polymer complex which was then coupled with MTX to give MM-MTX II; (C) MM-MTX IIIA were prepared by reacting MTX with amino-terminated magnetic microspheres, commercially available, in the presence of 1-ethyl-3,3-bis(methylamino)propylcarbodiimide (EDCI); (D) reaction of aminohexanol with di-tert-butyl dicarbonate to form an [N-(tert-butoxycarbonyl)amino]hexanol (t-Boc-AH), which was then coupled with MTX in the presence of 1,3-dicyclohexylcarbodiimide and 4-pyrrolidinopyridine to give a t-Boc-AH-MTX conjugate, which was then saturated with hydrogen chloride to give an aminohexanol-methotrexate (AH-MTX) conjugate. MM-MTX IIIB were then prepared by reacting AH-MTX with carboxyl-terminated magnetic microspheres, commercially available, in the presence of EDCI and 4-(dimethylamino)pyridine. The identity of MTX conjugates was confirmed using ultraviolet, infrared, and nuclear magnetic resonance spectroscopy. Drug content of the magnetic microsphere-methotrexate conjugates as determined by HPLC was 0.45% (w/w), 4.0% (w/w), and 6.3% (w/w) MTX for MM-MTX I, MM-MTX II, and MM-MTX IIIB, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue distribution of methotrexate following administration as a solution and as a magnetic microsphere conjugate in rats bearing brain tumors.

A novel magnetic microsphere-methotrexate (MM-MTX) drug delivery system was synthesized and evaluated in rats bearing rat glioma-2 (RG-2) tumors. Methotrexate was linked to the surface of the magnetic particle via an aminohexanol linker that would release free drug following hydrolysis. Male Fischer 344 rats bearing RG-2 tumors were administered 3 mg/kg of methotrexate (MTX) either as MM-MTX or as a solution (MTX-S) over 5 min. A 6000 gauss magnetic field was applied for 15 min from the end of MM-MTX administrations. Serial sacrifices were conducted at 15 min, 30 min and 45 min after drug administrations, organs collected, and analyzed for total MTX by a radioassay. At all times, MTX right brain (ipsilateral), brain tumor, and left brain concentrations were approximately 3.5 to 5-fold greater in the MM-MTX group compared to the MTX-S group. MTX concentrations in all other organs were less following administration of MM-MTX than MTX-S except in lung at 30 and 45 min. The targeting efficacy, an index for site-specificity, for both MM-MTX and MTX-S were similar and indicated some enhancement in MTX localization in brain tumor. Confocal and conventional light microscopic analyses demonstrated a diffuse distribution of MM-MTX in tumor consistent with extravascular uptake, whereas a predominant capillary distribution of MM-MTX was observed in normal brain. Following 45 min, the animals treated with MM-MTX died possibly due to redistribution of particles to the lung. This toxicity was dose-dependent. High brain MTX concentrations coupled with extravascular uptake of MM-MTX provide a basis for further investigations with this novel drug delivery system.