Pharmacokinetics and pharmacodynamics of single and multiple doses of the glucagon receptor antagonist LGD-6972 in healthy subjects and subjects with type 2 diabetes mellitus.

AIM: To evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of single and multiple doses of a novel, oral glucagon receptor antagonist, LGD-6972, in healthy subjects and subjects with type 2 diabetes (T2DM). METHODS: In the single ascending dose study, LGD-6972 (2-480 mg) was administered to healthy subjects (n = 48) and T2DM subjects (n = 8). In the multiple ascending dose study, healthy subjects (n = 12) received a dose of 15 mg LGD-6972 and T2DM subjects (n = 36) received doses of 5, 10 or 15 mg of LGD-6972 daily for 14 days. RESULTS: LGD-6972 had linear plasma pharmacokinetics consistent with once-daily dosing that was comparable in healthy and T2DM subjects. Dose-dependent decreases in fasting plasma glucose were observed in all groups with a maximum of 3.15 mmol/L (56.8 mg/dL) on day 14 in T2DM subjects. LGD-6972 also reduced plasma glucose in the postprandial state. Dose-dependent increases in fasting plasma glucagon were observed, but glucagon levels decreased and insulin levels increased after an oral glucose load in T2DM subjects. LGD-6972 was well tolerated at the doses tested without dose-related or clinically meaningful changes in clinical laboratory parameters. No subject experienced hypoglycaemia. CONCLUSION: Inhibition of glucagon action by LGD-6972 was associated with decreases in glucose in both healthy and T2DM subjects, the magnitude of which was sufficient to predict improvement in glycaemic control with longer treatment duration in T2DM patients. The safety and pharmacological profile of LGD-6972 after 14 days of dosing supports continued clinical development.

Phase IIa cross-over study of propylene glycol-free melphalan (LGD-353) and alkeran in multiple myeloma autologous transplantation.

Propylene Glycol-Free melphalan HCL for Injection (PGF-Mel) is a new formulation that incorporates Captisol, a specially modified cyclodextrin, to improve melphalan stability. In this phase IIa, open-label, randomized, cross-over design bioequivalence study, the pharmacokinetics of PGF-Mel were compared with the marketed formulation of melphalan, or Alkeran. Patients received half of the total dose of melphalan in the form of Alkeran and the other half in the form of PGF-Mel in an alternating manner. The pharmacokinetic measures were determined using WinNonlin 6.2 and bioequivalence was assessed using log-transformed systemic exposure parameters. Twenty-four patients, 11 females and 13 males, were enrolled between 4 February 2010 and 16 May 2011 at The University of Kansas Medical Center and The University of Kansas Cancer Center. The median age of enrolled subjects was 58 years (range: 48-65). All patients achieved myeloablation 3 days post autologous graft followed by successful neutrophil engraftment with a median of 11 days after transplant. Pharmacokinetic analysis showed that PGF-Mel was bioequivalent with Alkeran and also revealed that maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) were higher (~10%) after PGF-Mel administration. In conclusion, PGF-Mel is considered bioequivalent to Alkeran while also demonstrating a marginally higher systemic drug exposure.

The effects of substituted cyclodextrins on the colloidal and conformational stability of selected proteins.

The effects of various types of substituted and nonsubstituted cyclodextrins (CDs) on the physical and colloidal stability of three different proteins were studied to further ascertain the mechanism by which cyclodextrins stabilize proteins. The three proteins examined in this study are the Clostridium difficile Toxoid A, Yersinia pestis low-calcium-response V or V antigen (LcrV), and fibroblast growth factor 10 (FGF-10). These three pharmaceutically relevant proteins differ in molecular weight, pI, as well as in their secondary and tertiary structure. The effects of three parent cyclodextrins (alpha, beta, and gamma), as well as several hydroxypropyl (HP-CDs) and sulfobutylether (SBE-CDs) cyclodextrins of varying degrees of substitution, on the three proteins were examined as a function of pH and temperature. Structural changes and aggregation behavior were monitored in the presence and absence of the 17 cyclodextrins using circular dichroism, intrinsic fluorescence spectroscopy, and static light scattering. Overall, the major effect of the cyclodextrins on the proteins was the ability of a majority of them to inhibit thermally induced aggregation. This study suggests that the stabilization of proteins by cyclodextrins is dictated by their type and degree of substitution, as well as the physical and chemical properties of the protein being examined.

Evaluation of sustained/controlled-release dosage forms of 3-hydroxy-3-methylglutaryl-coenzyme a (HMG-CoA) reductase inhibitors in dogs and humans.

Seven sustained/controlled-release dosage forms were designed for gastrointestinal delivery of lovastatin or simvastatin, two potent HMG-CoA reductase inhibitors for the treatment of hypercholesterolemia. The in vivo performance of these formulations was evaluated in dogs and healthy volunteers in terms of the cholesterol lowering efficacy and/or systemic concentrations of HMG-CoA reductase inhibitors. Results from the present and previous studies suggest that, through the controlled release of HMG-CoA reductase inhibitors, sustained lower plasma concentrations of HMG-CoA reductase inhibitors may result in an equal or better therapeutic efficacy.

Enhanced bioavailability of cefoxitin using palmitoylcarnitine. II. Use of directly compressed tablet formulations in the rat and dog.

The performance of tablets containing the absorption enhancer palmitoylcarnitine chloride (PCC) and the antibiotic cefoxitin (CEF) was determined by direct placement of tablets in the rat stomach, small intestine, and colon. While the bioavailability (F) of tablets containing 12 mg CEF without PCC ranged from 0.6 to 3.9%, the addition of 24 mg PCC resulted in an enhanced CEF bioavailability in the rat colon (mean +/- SD: F = 57 +/- 19%) and rat jejunum (F = 71 +/- 16%) but not in the rat stomach. Following oral administration to dogs, tablets of 200 mg CEF without or with 600 mg PCC resulted in the same low bioavailabilities (7.0 +/- 10.3 and 7.0 +/- 3.6%, respectively). However, when these tablets were enteric coated, PCC improved CEF bioavailability from 2.44 +/- 1.84 to 29.0 +/- 13.4%. Therefore, the use of enteric-coated direct compressed tablets containing PCC and direct compression excipients improved the peroral bioavailability of a poorly absorbed compound.

Application site dependent ocular absorption of timolol.

Ocular absorption of timolol in rabbits was studied after topical ocular administration of 3H-timolol in an eyedrop or in silicone cylindrical devices that released timolol at 7.2 micrograms/h. The devices were applied in either the inferior or superior conjunctival sac. Timolol concentrations were nearly equal in the inferior and superior portions of ocular tissues when the drug was administered in an eyedrop. Administration in the devices resulted in unequal timolol distribution in the cornea, conjunctiva, sclera, and iris-ciliary body. Timolol concentrations were higher in the part of each tissue that was closer to the site of the device application. Unequal concentrations of timolol in the superior and inferior part of the eye and very low timolol concentrations in the aqueous humor indicated that timolol was absorbed mainly via a noncorneal route from the device placed in the inferior conjunctival sac. Induced blinking at one minute intervals did not change ocular absorption of timolol. Compared with inferior conjunctival sac applications, placement of the devices in the superior conjunctival sac resulted in increased corneal and total ocular absorption of timolol as indicated by higher timolol concentrations in the aqueous humor and by a smaller difference between concentrations in the superior and inferior portions of the examined tissues. The application site dependent ocular absorption indicated that controlled release of timolol in the tear fluid did not result in a uniform timolol distribution in the preocular tear fluid of rabbit eyes.

Dissolution and ionization of warfarin.

It has been shown in recent studies that warfarin exists in the solid state and in some nonaqueous solvents as a cyclic hemiketal. The present study was undertaken to investigate the ionization and ionization kinetics of warfarin, to confirm the probable existence of the cyclic hemiketal in aqueous solution, and to determine the possible consequences of the cyclic hemiketal to acyclic enol equilibrium and ionization kinetics on the dissolution rate of warfarin. The equilibrium aqueous solubility of un-ionized warfarin acid at 25 degrees C and ionic strength 0.5 (with potassium chloride) was found to be 1.28 X 10(-5) M, and its observed macroscopic pK alpha was 5.03-5.06, depending on the method of determination. By comparing the aqueous pK alpha of warfarin to phenprocoumin, a hydroxycoumarin that cannot exist in the cyclic hemiketal form, the hemiketal-acyclic enol ratio was estimated to be approximately 20:1. By stop-flow spectrophotometry, the ionization rate of warfarin (pH 3.5 jumped to pH 6.5) was found to have t1/2 less than 1-2 X 10(-3) s. The dissolution rate of warfarin from a rotating disk (600 rpm), as a function of pH, was measured under nonbuffered but pH-stat conditions (mu = 0.5 with potassium chloride). The pH-dissolution rate profile for warfarin agreed with that calculated from an equation derived previously to describe the dissolution of instantaneous ionizing acids, i.e., the profile was not perturbed from that expected from an acid of aqueous solubility 1.28 X 10(-5) M (un-ionized form) and pK alpha 5.06.

Thiamine whole blood and urinary pharmacokinetics in rats: urethan-induced dose-dependent pharmacokinetics.

The whole blood pharmacokinetics of thiamine after intravenous administration of thiamine hydrochloride (4, 12, and 36 mg/kg) to rats anesthetized continuously with ether (inhalation) or urethan (1 g/kg ip) were studied. Urinary excretion of thiamine after intravenous administration of thiamine hydrochloride to rats lightly anesthetized with ether was also investigated. At any particular dose, thiamine displayed apparent classical two-compartment model behavior in the time range studied. Under urethan anesthesia, thiamine displayed apparent dose-dependent kinetics as measured by the changes in the pharmacokinetic parameters, AUC,Vd(area), t0.5 beta, and total body clearance, ClTB, with dose. However, when ether anesthesia was used, thiamine displayed dose-independent pharmacokinetic behavior. These results suggest that care should be taken in the interpretation of pharmacokinetic data obtained in anesthetized animals, particularly when urethan anesthesia is used.

Thiamine whole blood pharmackinetics in rats using both a specific S-thiamine liquid scintillation assay and the thiochrome fluorescence assay.

The study of factors altering the CNS and GI absorption of thiamine in rats required the development of a specific assay for thiamine from 100-microliter samples of blood and plasma and small quantities of tissue. The specific thiochrome fluorescence assay for thiamine was modified to handle microsamples and to use S-thiamine. This sensitive and specific radioassay using S-thiamine gave pharmacokinetic parameters for 4-mg/kg iv doses of thiamine in rats equivalent to those using the less sensitive thiochrome fluorescence assay. The new assay, because of its lower limit of detection, allowed the study of the time profile of thiamine after a 1-mg/kg iv dose in rats. Such a time profile could not have been followed using the standard thiochrome fluorescence assay.

Phenylbutazone ionization kinetics.

Phenylbutazone has been associated with bioavailability problems and has shown nonclassical behavior in phase-transport studies. This nonclassical behavior has been attributed, in part, to the fact that phenylbutazone, as a carbon acid, undergoes noninstantaneous ionization kinetics. Instantaneous reaction is an assumption made in many diffusion-limited transport models involving a simultaneous ionization reaction. The ionization kinetics of phenylbutazone were determined at an ionic strength of 0.1 and 25 degrees using a stopped-flow spectrophotometer. A log kobs versus pH profile for the approach to the ionization equilibrium was determined, and a mechanism consistent with the profile was postulated. The percent enol versus the diketo form of phenylbutazone acid as well as pKaenol and pKadiketo was kinetically calculated. The protonation reaction was highly catalyzed by general acids while the deprotonation reaction was highly catalyzed by general bases. The general acid, water, was a poor proton donor to the anionic form (the so-called mesomericanion) of phenylbutazone.