Population pharmacokinetic-pharmacodynamic modeling analysis of intrinsic FXa and bleeding from edoxaban treatment.

Edoxaban is an oral, once-daily, direct factor Xa (FXa) inhibitor that has been evaluated for the prevention of stroke in patients with atrial fibrillation (AF) and for the treatment and prevention of venous thromboembolism (VTE) recurrence. Pharmacokinetic (PK) and pharmacodynamic (PD) modeling and logistic regression analyses were used to explore the clinical data from phase 1 and 2 studies to determine the relationship among PK exposure, PD response, and bleeding risk. Population PK/PD modeling was performed using plasma edoxaban concentration data from combined phase 1 and 2 studies and using intrinsic FXa data from a phase 2 AF study. A 2-compartment PK model adequately described the combined PK data, and a dynamic binding model characterized the dynamics of the intrinsic factor X activity (iFXa) data. Logistic regression analysis then identified the relationship between the iFXa and the observed bleeding risk. The more protracted suppression of FXa over the dosing interval for a 30-mg twice-daily dose compared with a 60-mg once-daily dose offers an explanation for the significantly higher bleeding rate at the former dose.

Model-Supported Development of CS-8635: A Fixed-Dose Combination of Olmesartan, Amlodipine, and Hydrochlorothiazide.

CS-8635, a fixed-dose triple combination of olmesartan, amlodipine, and hydrochlorothiazide, was developed to address the growing need for additional blood pressure (BP) reduction in patients not controlled with dual-combination therapies. Prior to Phase III, modeling and simulation (M&S) was conducted to estimate the additional BP lowering effect of CS-8635 compared to the respective dual combinations. The Phase III study evaluated CS-8635 BP lowering effects only at the highest dose strength among the five dose strengths to be developed. Post-trial M&S was performed using an integrated dataset from three Phase III programs; CS-8635 plus two prior dual combinations. M&S robustly estimated and described the BP lowering effects of CS-8635 evaluated in a clinical setting. Furthermore, M&S evaluated BP lowering effects of the additional four dose strengths not studied. In summary, M&S aided the development of the clinical study and full characterization of the BP lowering effects of CS-8635 across intermediate doses.

Pharmacokinetics of olmesartan medoxomil in pediatric patients with hypertension.

BACKGROUND: The prevalence and importance of hypertension in younger patients is becoming increasingly recognized; however, only a limited number of clinical trials have been conducted in the pediatric population. OBJECTIVE: The aim of this study was to characterize the pharmacokinetics and short-term safety of olmesartan medoxomil in children and adolescents with hypertension. METHODS: An open-label, multicenter, single-dose study was conducted in children and adolescents aged 12 months-16 years who were receiving treatment for hypertension or, if not currently treated for hypertension, had either a systolic blood pressure (SBP) or diastolic blood pressure (DBP).≥95th percentile, or SBP or DBP ≥90th percentile if diabetic or with a family history of hypertension. Patients were stratified by age: 12-23 months (Group 1; none enrolled), 2-5 years (Group 2; n = 4), 6-12 years (Group 3; n = 10), and 13-16 years (Group 4; n = 10). All patients received a single oral dose of olmesartan medoxomil based on the individual's age and bodyweight. Patients aged <6 years received an oral suspension of olmesartan medoxomil at a dose of 0.3 mg/kg of bodyweight (not to exceed 20 mg), those aged ≥6 years who weighed ≥35 kg received olmesartan medoxomil 40 mg tablets, and those who weighed <35 kg received olmesartan medoxomil 20 mg tablets. RESULTS: In Groups 2, 3, and 4, the weight-adjusted apparent total body clearance (CL/F) of olmesartan medoxomil was 0.100 ± 0.034, 0.062 ± 0.020, and 0.072 ± 0.022 L/h/kg, respectively, and the weight-adjusted apparent volume of distribution (Vd/F) was 0.32 ± 0.16, 0.33 ± 0.14, and 0.49 ± 0.23 L/kg, respectively. CL/F and Vd/F in Groups 3 and 4 were not significantly different. Statistical comparisons between Groups 3 or 4 and Group 2 were not performed due to the small sample size of Group 2 (n = 4). Plasma elimination half-life and time to maximum plasma concentration were similar across the three groups. In Groups 3 and 4, considerable interindividual variability was seen in maximum plasma concentration (C(max)), area under the curve (AUC) from time zero to the last measurable concentration, and apparent clearance, with AUC and C(max) approximately 30% greater in Group 3. Four of 24 (16.7%) patients experienced treatment-emergent adverse events that were all mild in severity and considered not drug-related. No deaths, serious adverse events, or discontinuations due to adverse events occurred in the study. CONCLUSIONS: Olmesartan medoxomil was well tolerated and demonstrated a pharmacokinetic profile in pediatric patients similar to that of adults when adjusted for body size. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00151814

Modelling and simulation of edoxaban exposure and response relationships in patients with atrial fibrillation.

Edoxaban is a novel, orally available, highly specific direct inhibitor of factor Xa and is currently being developed for the treatment and prevention of venous thromboembolism and prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation (NVAF). The objectives of the present analyses were to characterise edoxaban population pharmacokinetics (PPK) and identify potential intrinsic and extrinsic factors affecting variability in edoxaban exposure, determine if there are relationships between edoxaban pharmacokinetics or biomarkers and the risk of bleeding in patients with NVAF using an exposure-response model, and to use the PPK and exposure-response model to support dose selection for a phase III trial of edoxaban in patients with NVAF. PPK analysis of data from 1,281 edoxaban-dosed subjects with intrinsic factors such as renal impairment or NVAF and extrinsic factors such as concomitant medications revealed significant effects of renal impairment and concomitant strong P-glycoprotein (P-gp) inhibitors on the pharmacokinetics of edoxaban. Exposure-response analysis found that in patients with NVAF, the incidence of bleeding events increased significantly with increasing edoxaban exposure, with steady-state minimum concentration (Cmin,ss) showing the strongest association. Clinical trial simulations of bleeding incidence were used to select 30 mg and 60 mg once-daily edoxaban with 50% dose reductions for patients with moderate renal impairment or receiving concomitant strong P-gp inhibitors as the treatment regimens in the ENGAGE AF-TIMI 48 (NCT00781391) trial.

Low dose suramin as a chemosensitizer of bladder cancer to mitomycin C.

PURPOSE: We have reported that acidic and basic fibroblast growth factors expressed in solid tumors induce broad-spectrum chemoresistance and their nonspecific inhibitor suramin (Sigma Chemical Co., St. Louis, Missouri) at nontoxic concentrations enhances the activity of chemotherapeutic agents. In the current study we evaluated whether low dose suramin enhances tumor sensitivity to mitomycin C (MMC) (Bristol-Myer Squibb Co., Wallingford, Connecticut). MATERIALS AND METHODS: Three-dimensional histocultures of RT4 (American Type Culture Collection, Rockville, Maryland) xenograft tumors and tumors from patients with bladder cancer were treated with MMC with or without 20 microM suramin. For in vivo studies mice bearing RT4 tumors received physiological saline, MMC (3 mg/kg), suramin (10 mg/kg) or MMC/suramin combination every 3 or 4 days. Two MMC schedules were studied, namely subtherapeutic (3 treatments) and therapeutic (6 treatments) schedules. RESULTS: Suramin enhanced MMC activity in xenograft and patient tumor histocultures by greater than 2-fold. The chemosensitization effect was observed in all patient tumors (2 superficial and 9 muscle invading lesions). In animals tumors in the control and suramin groups increased to approximately 3 to 5 times the initial size. The subtherapeutic MMC schedule retarded tumor growth but did not produce tumor shrinkage, whereas the therapeutic MMC schedule reduced tumor size by 27%. The addition of suramin enhanced MMC activity. Respective tumor sizes were 40% and 63% of the sizes after subtherapeutic and therapeutic MMC alone (p <0.01). The combination groups showed body weight losses similar to those of MMC alone. CONCLUSIONS: Low dose suramin enhanced the in vitro and in vivo activity of subtherapeutic and therapeutic MMC without enhancing host toxicity, thus, providing proof of concept for evaluating low dose suramin as a chemosensitizer with MMC in bladder cancer.

Low-dose suramin enhanced paclitaxel activity in chemotherapy-naive and paclitaxel-pretreated human breast xenograft tumors.

We reported induction of broad-spectrum chemoresistance by acidic and basic fibroblast growth factors and chemosensitization by their nonspecific inhibitor suramin at nontoxic and subtherapeutic doses. This study evaluated whether low-dose suramin enhances paclitaxel activity in chemotherapy-naïve and paclitaxel-pretreated human MCF7 breast xenograft tumors in mice. Suramin, 10 mg/kg, and/or paclitaxel, 15 mg/kg, were administered intravenously, twice weekly for 2 to 3 weeks. In addition to conventional end points [tumor size change, median survival time (MST)], we also used clinically relevant end points [partial (PR) and complete response rates (CR); progressive disease (PD); stable disease (SD); time to tumor progression (TTP)]. In chemotherapy-naïve mice, the control and suramin groups showed identical TTP (3 days) and MST (21 days). Single-agent paclitaxel produced 47% PR and 24% CR, and prolonged both TTP and MST to 73 days. The addition of suramin further improved the total response rate to 100% with a dramatically greater 63% CR, shortened the time to attain PR and CR, and prolonged TTP and MST to > or =136 days. In the paclitaxel-pretreated group, single-agent paclitaxel resulted in 67% SD and 33% PD, whereas the combination produced 50% PR and 50% SD. Suramin also significantly enhanced the apoptotic effect of paclitaxel in tumors. In conclusion, suramin improved the activity of paclitaxel in both chemotherapy-naïve and paclitaxel-pretreated animals, without enhancing host toxicity (< or =10% body weight loss in all groups). These data have led to the initiation of phase I/II trials of paclitaxel and low-dose suramin combination in advanced metastatic breast cancer patients.

Phase I study of low-dose suramin as a chemosensitizer in patients with advanced non-small cell lung cancer.

PURPOSE: Our preclinical studies have shown that acidic and basic fibroblastic growth factors confer broad spectrum chemoresistance and that low concentrations (10-50 microM) of suramin, a nonspecific fibroblastic growth factor inhibitor, enhance the antitumor activity of paclitaxel in vivo. The present Phase I study evaluated low-dose suramin in combination with paclitaxel/carboplatin in advanced non-small cell lung cancer patients. EXPERIMENTAL DESIGN: Patients received suramin followed by paclitaxel (175-200 mg/m(2)) and carboplatin area under the concentration-time curve of 6 mg/ml/min, every 3 weeks. The initial suramin dose for the first cycle was 240 mg/m(2), and the doses for subsequent cycles were calculated based on the 72-h pretreatment plasma concentrations. The recommended suramin dose would yield plasma concentrations of 10-20 microM at 48 h in >or=5 of 6 patients. RESULTS: Fifteen patients (11 stage IV, 4 stage IIIB, 9 chemonaive, and 6 previously treated) received 85 courses. The most common toxicities were neutropenia, nausea/vomiting, malaise/fatigue, and peripheral neuropathy. No treatment-related hospitalizations, adrenal dysfunction, or episodes of sepsis occurred. The initial suramin dose resulted in the targeted concentrations of 10-20 microM at 48 h in 5 of the first 6 patients treated but also resulted in peak concentrations > 50 microM in all patients. Dividing the suramin dose to be administered in two doses, 24 h apart, yielded the target concentrations and avoided undesirable peak concentrations. Discernable antitumor activity occurred in 7 of 10 patients with measurable disease, including 2 with prior chemotherapy. The median time to tumor progression is 8.5 months (range, 3-27+ months) for 12 evaluable patients. CONCLUSIONS: Low-dose suramin does not increase the toxicity of paclitaxel/carboplatin combination. The suramin dose can be calculated based on clinical parameters. Because of the preliminary antitumor activity observed, efficacy studies in chemonaive and chemorefractory patients are under way.

Simultaneous targeting of telomeres and telomerase as a cancer therapeutic approach.

Telomeres, which are important for maintaining chromosome integrity and functions, shorten with each cell division. Telomerase, responsible for telomere synthesis, is expressed in approximately 90% of human tumor cells but seldom in normal somatic cells. This study evaluated the hypothesis that simultaneous shortening of telomeres and inhibition of telomerase results in synergistic and tumor-selective cytotoxicity. In telomerase-positive human pharynx FaDu tumor cells, paclitaxel caused telomere erosion (first detected at 1 h) and apoptosis. Expression of antisense to the RNA component of human telomerase (hTR) inhibited telomerase activity, shortened telomere length, reduced cell growth rate, and resulted in a significant higher sensitivity to paclitaxel. Another telomerase inhibitor, 3'-azido-3'-deoxythymidine (AZT), at a concentration that produced little or no cell detachment or apoptosis, inhibited the telomerase activity and enhanced the paclitaxel-induced cell detachment and apoptosis. AZT also enhanced the activity of paclitaxel in mice bearing well-established s.c. FaDu xenograft tumors (i.e., reduced residual tumor size, enhanced apoptotic cell fraction, and prolonged survival time), without enhancing host toxicity. In contrast, AZT did not enhance the paclitaxel activity in the telomerase-negative osteosarcoma Saos-2 cells nor in FaDu cells where telomerase was already suppressed by antisense hTR, confirming that the AZT effect in parent FaDu cells is mediated through telomerase inhibition. These results demonstrate that combined use of agents targeting both telomere and telomerase yielded synergistic activity selective for tumors that depend on telomerase for telomere maintenance.