Punam Sandhu

Disposition of Caspofungin: Role of Distribution in Determining Pharmacokinetics in Plasma

ABSTRACT The disposition of caspofungin, a parenteral antifungal drug, was investigated. Following a single, 1-h, intravenous infusion of 70 mg (200 μCi) of [3H]caspofungin to healthy men, plasma, urine, and feces were collected over 27 days in study A (n = 6) and plasma was collected over 26 weeks in study B (n = 7). Supportive data were obtained from a single-dose [3H]caspofungin tissue distribution study in rats (n = 3 animals/time point). Over 27 days in humans, 75.4% of radioactivity was recovered in urine (40.7%) and feces (34.4%). A long terminal phase (t1/2 = 14.6 days) characterized much of the plasma drug profile of radioactivity, which remained quantifiable to 22.3 weeks. Mass balance calculations indicated that radioactivity in tissues peaked at 1.5 to 2 days at ∼92% of the dose, and the rate of radioactivity excretion peaked at 6 to 7 days. Metabolism and excretion of caspofungin were very slow processes, and very little excretion or biotransformation occurred in the first 24 to 30 h postdose. Most of the area under the concentration-time curve of caspofungin was accounted for during this period, consistent with distribution-controlled clearance. The apparent distribution volume during this period indicated that this distribution process is uptake into tissue cells. Radioactivity was widely distributed in rats, with the highest concentrations in liver, kidney, lung, and spleen. Liver exhibited an extended uptake phase, peaking at 24 h with 35% of total dose in liver. The plasma profile of caspofungin is determined primarily by the rate of distribution of caspofungin from plasma into tissues.

Generation and selection of novel fully human monoclonal antibodies that neutralize Dickkopf-1 (DKK1) inhibitory function in vitro and increase bone mass in vivo

Wnt/LRP5 signaling is a central regulatory component of bone formative and resorptive activities, and the pathway inhibitor DKK1 is a suppressor of bone formation and bone mass accrual in mice. In addition, augmented DKK1 levels are associated with high bone turnover in diverse low bone mass states in rodent models and disease etiologies in human. However, examination of the precise role of DKK1 in the normal skeleton and in higher species requires the development of refined DKK1-specific pharmacological tools. Here, we report the strategy resulting in isolation of a panel of fully human anti-DKK1 antibodies applicable to studies interrogating the roles of mouse, rhesus, and human DKK1. Selected anti-DKK1 antibodies bind primate and human DKK-1 with picomolar affinities yet do not appreciably bind to DKK2 or DKK4. Epitopes mapped within the DKK1 C-terminal domain necessary for interaction with LRP5/6 and consequently effectively neutralized DKK1 function in vitro. When introduced into naïve normal growing female mice, IgGs significantly improved trabecular bone volume and structure and increased both trabecular and cortical bone mineral densities in a dose-related fashion. Furthermore, fully human DKK1-IgG displayed favorable pharmacokinetic parameters in non-human primates. In summary, we demonstrate here a rate-limiting function of physiologic DKK1 levels in the regulation of bone mass in intact female mice, amendable to specific pharmacologic neutralization by newly identified DKK1-IgGs. Importantly the fully human IgGs display a profile of attributes that recommends their testing in higher species and their use in evaluating DKK1 function in relevant disease models.

A Rate-Limiting Role for Dickkopf-1 in Bone Formation and the Remediation of Bone Loss in Mouse and Primate Models of Postmenopausal Osteoporosis by an Experimental Therapeutic Antibody

Genetic studies have linked both osteoporotic and high bone mass phenotypes to low-density lipoprotein receptor-related proteins (LRP4, LRP5, and LRP6). LRPs are receptors for inhibitory Dickkopf-1 (DKK1) protein, and treatment modalities that modulate LRP/DKK1 binding therefore may act as stimulators of bone mass accrual. Here, we report that RH2-18, a fully human monoclonal anti-DKK1 antibody elicits systemic pharmacologic bone efficacy and new bone formation at endosteal bone surfaces in vivo in a mouse model of estrogen-deficiency-induced osteopenia. This was paralleled by partial-to-complete resolution of osteopenia (bone mineral density) at all of the skeletal sites investigated in femur and lumbar-vertebral bodies and the restoration of trabecular bone microarchitecture. More importantly, testing of RH2-18 in adult, osteopenic rhesus macaques demonstrated a rate-limiting role of DKK1 at multiple skeletal sites and responsiveness to treatment. In conclusion, this study provides pharmacologic evidence for the modulation of DKK1 bioactivity in the adult osteopenic skeleton as a viable approach to resolve osteopenia in animal models. Thus, data described here suggest that targeting DKK1 through means such as a fully human anti-DKK1-antibody provides a potential bone-anabolic treatment for postmenopausal osteoporosis.

Disposition of Caspofungin, a Novel Antifungal Agent, in Mice, Rats, Rabbits, and Monkeys

ABSTRACT The metabolism, excretion, and pharmacokinetics of caspofungin (Cancidas; Merck & Co., Inc.) were investigated after administration of a single intravenous dose to mice, rats, rabbits, and monkeys. Caspofungin had a low plasma clearance (0.29 to 1.05 ml/min/kg) and a long terminal elimination half-life (11.7 h to 59.7 h) in all preclinical species. The elimination kinetics of caspofungin were multiphasic and displayed an initial distribution phase followed by a dominant β-elimination phase. The presence of low levels of prolonged radioactivity in plasma was observed and was partially attributable to the chemical degradation product M0. Excretion studies with [3H]caspofungin indicated that the hepatic and renal routes play an important role in the elimination of caspofungin, as a large percentage of the radiolabeled dose was recovered in urine and feces. Excretion of radioactivity in all species studied was slow, and low levels of radioactivity were detected in daily urine and fecal samples throughout a prolonged collection period. Although urinary profiles indicated the presence of several metabolites (M0, M1, M2, M3, M4, M5, and M6), the majority of the total radioactivity was associated with the polar metabolites M1 [4(S)-hydroxy-4-(4-hydroxyphenyl)-l-threonine] and M2 [N-acetyl-4(S)-hydroxy-4-(4-hydroxyphenyl)-l-threonine]. Caspofungin was thus primarily eliminated by metabolic transformation; however, the rate of metabolism was slow. These results suggest that distribution plays a prominent role in determining the plasma pharmacokinetics and disposition of caspofungin, as very little excretion or biotransformation occurred during the early days after dose administration, a period during which concentrations in plasma fell substantially. The disposition of caspofungin in preclinical species was similar to that reported previously in humans.

Clinical pharmacology profile of vorinostat, a histone deacetylase inhibitor

PurposeVorinostat is a histone deacetylase inhibitor that has demonstrated preclinical activity in numerous cancer models. Clinical activity has been demonstrated in patients with a variety of malignancies. Vorinostat is presently indicated for the treatment of patients with advanced cutaneous T cell lymphoma (CTCL). Clinical investigation is ongoing for therapy of other solid tumors and hematological malignancies either as monotherapy or in combination with other chemotherapeutic agents. This review summarizes the pharmacokinetic properties of vorinostat.MethodsMonotherapy pharmacokinetic data across a number of pharmacokinetic studies were reviewed, and data are presented. In addition, literature review was performed to obtain published Phase I and II pharmacokinetic combination therapy data to identify and characterize potential drug interactions with vorinostat. Pharmacokinetic data in special populations were also reviewed.ResultsThe clinical pharmacology profile of vorinostat is favorable, exhibiting dose-proportional pharmacokinetics and modest food effect. There appear to be no major differences in the pharmacokinetics of vorinostat in special populations, including varying demographics and hepatic dysfunction. Combination therapy pharmacokinetic data indicate that vorinostat has a low propensity for drug interactions.ConclusionsVorinostat’s favorable clinical pharmacology and drug interaction profile aid in the ease of administration of vorinostat for the treatment of advanced CTCL and will be beneficial in continued assessment for other oncologic indications. Although a number of studies have been conducted to elucidate the detailed pharmacokinetic profile of vorinostat, more rigorous assessment of vorinostat pharmacokinetics, including clinical drug interaction studies, will be informative.

Disposition of vorinostat, a novel histone deacetylase inhibitor and anticancer agent, in preclinical species.

The disposition of vorinostat, an anticancer agent, was investigated in rats and dogs. Vorinostat possessed high serum clearance, a short elimination half-life and low oral bioavailability in both species. The renal route played an important role in the elimination of drug-related material and vorinostat was eliminated primarily by metabolic biotransformation.

Efficacy of Caspofungin in a Juvenile Mouse Model of Central Nervous System Candidiasis

ABSTRACT Neonatal candidiasis is an increasingly common occurrence causing significant morbidity and mortality and a higher risk of dissemination to the central nervous system (CNS) than that seen with older patients. The current understanding of optimal antifungal therapy in this setting is limited. We have developed a model of disseminated candidiasis with CNS involvement in juvenile mice to assess the efficacy of the echinocandin caspofungin relative to amphotericin B (AmB). Juvenile mice were inoculated intravenously with 5.64 × 104 CFU of Candida albicans MY1055. Treatment with caspofungin at 1, 2, 4, and 8 mg/kg of body weight/day, AmB at 1 mg/kg/day, or a vehicle control (VC) was initiated 30 h after infection and continued for 7 days. Pharmacokinetic parameters for caspofungin were also determined. Culture and histology showed evidence of disseminated candidiasis with multifocal encephalitis at the start of antifungal therapy. Survival was 100% in all treated groups, while mortality was 100% in the VC by day 11 after infection. By day 5, all mice in the caspofungin treatment (four doses) groups showed reductions in kidney and brain burden relative to the VC, while AmB treatment reduced kidney burden but gave no reduction of brain fungal burden. Systemic levels of caspofungin were similar in infected and uninfected mice, while brain levels were higher in infected animals. In this juvenile mouse model, caspofungin demonstrated dose-dependent activity, equivalent to or better than that of AmB at 1 mg/kg, against disseminated candidiasis with CNS involvement.

Physiologically Based Pharmacokinetic Model Qualification and Reporting Procedures for Regulatory Submissions: A Consortium Perspective

This work provides a perspective on the qualification and verification of physiologically based pharmacokinetic (PBPK) platforms/models intended for regulatory submission based on the collective experience of the Simcyp Consortium members. Examples of regulatory submission of PBPK analyses across various intended applications are presented and discussed. European Medicines Agency (EMA) and US Food and Drug Administration (FDA) recent draft guidelines regarding PBPK analyses and reporting are encouraging, and to advance the use and acceptability of PBPK analyses, more clarity and flexibility are warranted.

PHARMACOKINETICS AND PHARMACODYNAMICS TO SUPPORT CLINICAL STUDIES OF MK-8719: AN O-GLCNACASE INHIBITOR FOR PROGRESSIVE SUPRANUCLEAR PALSY

generative disease. Stress is implicated in the development of AD since oxidative stress has been linked to cognitive impairment. Epigallocatechin-3-gallate (EGCG) is the most abundant catechin in green tea and has antioxidant, anti-inflammatory and anti-atherogenic effects, while Diazepam is an anxiolytic with promising neuroprotective properties. Methods: Seven groups (8 rats/ group) were daily IP injected for six week either with saline for control (2 groups) or with 70 mg/kg ALCL3 for AD-induced model (5 groups). Stress was induced for all groups except one control and one ALCL3 group by exposing rats 6 times during six weeks to Stress-induced box paradigm (1time/ week for 30 minute). Three groups of AD-induced model were also daily received either EGCG (10mg/kg, IP), Diazepam (0.1mg/kg, IP) or their combination. All rats were examined in two behavioral experiments; Morris water maze task and Conditioned-avoidance learning test. Histological examination was achieved in different brain regions and biochemical measurements as brain cholinergic markers (ACHE); oxidative stress markers (SOD, GSH-Px, MDA, TAC) and inflammatory mediators (TNF-a, IL-1b) were also assayed for all groups. Results: Rats exposed to ALCL3 together with stress showed marked decline in learning and memory abilities. Stress also induced significant elevation in hippocampus TNF-a, IL-1b andMDA level as well as in ACHE activity accompanied by reduction in GSH-Px, TAC and SOD activities. Marked histopathological brain degenerations were also shown in AD-model group exposed to stress. EGCG showed more marked protective effect than Diazepam from stress-potentiated the deleterious effect of ALCL3 on the brain, however Co-administration of both resulted in more pronounced protection as regarding all measured parameters. Conclusions:Exposure to stress represents a risk factor in induction and progression of AD. The deleterious effect of stress on the brain and hippocampus can be counteracted by Co-administration of both EGCG and Diazepam.

Application of Physiologically‐Based Pharmacokinetic Modeling to Predict Pharmacokinetics in Healthy Japanese Subjects

Pharmacokinetics (PKs) in Japanese healthy subjects were simulated for nine compounds using physiologically based PK (PBPK) models parameterized with physicochemical properties, preclinical absorption, distribution, metabolism, and excretion (ADME) data, and clinical PK data from non‐Japanese subjects. For each dosing regimen, 100 virtual trials were simulated and predicted/observed ratios for peak plasma concentration (Cmax) and area under the curve (AUC) were calculated. As qualification criteria, it was prespecified that >80% of simulated trials should demonstrate ratios to observed data ranging from 0.5–2.0. Across all compounds and dose regimens studied, 93% of simulated Cmax values in Japanese subjects fulfilled the criteria. Similarly, for AUC, 77% of single‐dosing regimens and 100% of multiple‐dosing regimens fulfilled the criteria. In summary, mechanistically incorporating the appropriate ADME properties into PBPK models, followed by qualification using non‐Japanese clinical data, can predict PKs in the Japanese population and lead to efficient trial design and conduct of Japanese phase I studies.