A Novel Design for Decision Rules Based on Statistical Testing Strategies of Binary Endpoints in a Definitive Go/No-Go Single-Treatment Clinical Study.

In drug development, a definitive go/no-go clinical study is sometimes conducted before major investment is made to advance the development into the next stage. Such a study sometimes focuses on a key binary endpoint, such as a particular adverse event, treatment failure, or device problem. However, such a study is often constrained by budget and scope, which limit the sponsor's ability to draw clear conclusions. This paper proposes a novel design that uses Wilson confidence intervals to devise statistical testing strategies that allow the decision makers to arrive at certain definite conclusions within the constraint of the study's scope.

Pharmacokinetics and pharmacodynamics of exenatide extended-release after single and multiple dosing.

BACKGROUND AND OBJECTIVES: Exenatide is a glucagon-like peptide-1 receptor agonist, available in an immediate-release (IR), twice-daily formulation, which improves glycaemic control through enhancement of glucose-dependent insulin secretion, suppression of inappropriately elevated postprandial glucagon secretion, slowing of gastric emptying and reduction of food intake. The objectives of these studies were to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of an extended-release (ER) exenatide formulation in patients with type 2 diabetes mellitus. PATIENTS AND METHODS: Patients with type 2 diabetes participated in either a single-dose trial (n = 62) or a repeated-administration trial (n = 45). The pharmacokinetic and safety effects of single-dose subcutaneous administration of exenatide ER (2.5 mg, 5 mg, 7 mg or 10 mg) versus placebo were studied over a period of 12 weeks in patients with type 2 diabetes. These results were used to predict the dose regimen of exenatide ER required to achieve steady-state therapeutic plasma exenatide concentrations. A second clinical study investigated the pharmacokinetics, pharmacodynamics and safety of weekly exenatide ER subcutaneous injections (0.8 mg or 2 mg) versus placebo in patients with type 2 diabetes over a period of 15 weeks. Furthermore, population-based analyses of these studies were performed to further define the exposure-response relationships associated with exenatide ER. RESULTS: Exenatide exposure increased with dose (2.5 mg, 5 mg, 7 mg or 10 mg) and exhibited a multiple-peak profile over approximately 10 weeks. Multiple-dosing pharmacokinetics were predicted from superpositioning of single-dose data; weekly administration of exenatide ER 0.8 mg and 2 mg for 15 weeks confirmed the predictions. Weekly dosing resulted in steady-state plasma exenatide concentrations after 6-7 weeks. Fasting plasma glucose levels were reduced similarly with both doses after 15 weeks (-42.7 ± 15.7 mg/dL with the 0.8 mg dose and -39.0 ± 9.3 mg/dL with the 2 mg dose; both p < 0.001 vs placebo), and the integrated exposure-response analysis demonstrated that the drug concentration producing 50% of the maximum effect (EC(50)) on fasting plasma glucose was 56.8 pg/mL (a concentration achieved with both the 0.8 mg and 2 mg doses of exenatide ER). The 2 mg dose reduced bodyweight (-3.8 ± 1.4 kg; p < 0.05 vs placebo) and postprandial glucose excursions. Glycosylated haemoglobin (HbA(1c)) levels were reduced with the 0.8 mg dose (-1.4 ± 0.3%; baseline 8.6%) and with the 2 mg dose (-1.7 ± 0.3%; baseline 8.3%) [both p < 0.001 vs placebo]. Adverse events were generally transient and mild to moderate in intensity. CONCLUSION: These studies demonstrated that (i) a single subcutaneous dose of exenatide ER resulted in dose-related increases in plasma exenatide concentrations; (ii) single-dose exposure successfully predicted the weekly-dosing exposure, with 0.8 mg and 2 mg weekly subcutaneous doses of exenatide ER eliciting therapeutic concentrations of exenatide; and (iii) weekly dosing with either 0.8 or 2 mg of exenatide ER improved fasting plasma glucose control, whereas only the 2 mg dose was associated with improved postprandial glucose control and weight loss. [Clinicaltrials.gov Identifier: NCT00103935].

DURATION-1: exenatide once weekly produces sustained glycemic control and weight loss over 52 weeks.

OBJECTIVE: In the Diabetes Therapy Utilization: Researching Changes in A1C, Weight and Other Factors Through Intervention with Exenatide Once Weekly (DURATION-1) study, the safety and efficacy of 30 weeks of treatment with the glucagon-like peptide-1 receptor agonist exenatide once weekly (exenatide QW; 2 mg) was compared with exenatide BID in 295 patients with type 2 diabetes. We now report the safety and efficacy of exenatide QW in 1) patients who continued treatment for an additional 22 weeks (52 weeks total) and 2) patients who switched from exenatide BID to exenatide QW after 30 weeks. RESEARCH DESIGN AND METHODS: In this randomized, multicenter, comparator-controlled, open-label trial, 258 patients entered the 22-week open-ended assessment phase (n = 128 QW-only; n = 130 BID-->QW). A1C, fasting plasma glucose (FPG), body weight, blood pressure, fasting lipids, safety, and tolerability were assessed. RESULTS: Patients continuing exenatide QW maintained A1C improvements through 52 weeks (least squares mean -2.0% [95% CI -2.1 to -1.8%]). Patients switching from exenatide BID to exenatide QW achieved further A1C improvements; both groups exhibited the same A1C reduction and mean A1C (6.6%) at week 52. At week 52, 71 and 54% of all patients achieved A1C <7.0% and 40 mg/dl, and body weight was reduced by >4 kg after 52 weeks. Nausea occurred less frequently in this assessment period and was predominantly mild. No major hypoglycemia was observed. CONCLUSION: Exenatide QW elicited sustained improvements in glycemic control and body weight through 52 weeks of treatment. Patients switching to exenatide QW experienced further improvements in A1C and FPG, with sustained weight loss.

Enhanced weight loss following coadministration of pramlintide with sibutramine or phentermine in a multicenter trial.

Preclinical evidence suggests that pharmacotherapy for obesity using combinations of agents targeted at distinct regulatory pathways may produce robust additive or synergistic effects on weight loss. This randomized placebo-controlled trial examined the safety and efficacy of the amylin analogue pramlintide alone or in combination with either phentermine or sibutramine. All patients also received lifestyle intervention. Following a 1-week placebo lead-in, 244 obese or overweight, nondiabetic subjects (88% female; 41 +/- 11 years; BMI 37.7 +/- 5.4 kg/m(2); weight 103 +/- 19 kg; mean +/- s.d.) received placebo subcutaneously (sc) t.i.d., pramlintide sc (120 microg t.i.d.), pramlintide sc (120 microg t.i.d.) + oral sibutramine (10 mg q.a.m.), or pramlintide sc (120 microg t.i.d.) + oral phentermine (37.5 mg q.a.m.) for 24 weeks. Treatment was single-blind for subjects receiving subcutaneous medication only and open-label for subjects in the combination arms. Weight loss achieved at week 24 with either combination treatment was greater than with pramlintide alone or placebo (P < 0.001; 11.1 +/- 1.1% with pramlintide + sibutramine, 11.3 +/- 0.9% with pramlintide + phentermine, -3.7 +/- 0.7% with pramlintide; -2.2 +/- 0.7% with placebo; mean +/- s.e.). Elevations from baseline in heart rate and diastolic blood pressure were demonstrated with both pramlintide + sibutramine (3.1 +/- 1.2 beats/min, P < 0.05; 2.7 +/- 0.9 mm Hg, P < 0.01) and pramlintide + phentermine (4.5 +/- 1.3 beats/min, P < 0.01; 3.5 +/- 1.2 mm Hg, P < 0.001) using 24-h ambulatory monitoring. However, the majority of subjects receiving these treatments remained within normal blood pressure ranges. These results support the potential of pramlintide-containing combination treatments for obesity.

A Bayesian approach to utilizing prior data in new drug development.

In this paper we propose a Bayesian method to combine safety data collected from two separate drug development programs using the same active drug substance but for different indications, formulations, or patient populations. The objective of combining the data across the programs is to better define the level of safety risk associated with the new indication or target population. There may be adverse events (AEs) observed in the new program that represent new safety signals. Our method is to explore the AEs using data from both development programs. Our approach utilizes data collected previously to assist in analyzing safety data from the new program. It is assumed that the frequency of a certain AE follows a distribution with a parameter that characterizes the safety risk level. The parameter is assumed to follow a distribution function. In the Bayesian framework, this distribution function is called a prior distribution in the absence of data and posterior distribution when updated by real data. The key concept behind our method is to use data from the previous program to construct a posterior distribution that will in turn serve as a prior distribution for the new program. The construction of this updated prior down weights data from the previous program to emphasize the new program and thus avoids simple pooling of the data across programs. Such "soft use" of previous information minimizes the potential for undue influence of previous data on the analysis. Data from the new program are used to update the prior distribution and compute the posterior distribution for the new program. Key statistics are then calculated from the posterior distribution to quantify the risk level for the new program. We have tested the proposed approach using data from a real Phase 2 study that was conducted as part of a clinical development program for a new indication of an approved drug. The results indicate that the estimated risk level was affected both by the observed event rates and the extents of exposure across the two development programs. This approach appropriately characterizes the safety profile across the two development programs and properly contextualizes new safety signals from the new program.

Effectiveness of progressive dose-escalation of exenatide (exendin-4) in reducing dose-limiting side effects in subjects with type 2 diabetes.

BACKGROUND: Exenatide (exendin-4) exhibits dose-dependent glucoregulatory activity, but causes dose-limiting nausea and vomiting. This study was designed to formally assess the possibility of inducing tolerance to the side effects of nausea and vomiting at therapeutic doses of exenatide, using a dose-escalation methodology. METHODS: In this two-arm, triple-blind, multicenter study, 123 subjects with type 2 diabetes were enrolled and randomized; 99 (80.5%) of them completed the study. Subjects in the exenatide-primed arm received subcutaneous exenatide, starting at 0.02 micro g/kg three times a day (TID) and increasing in 0.02 micro g/kg per dose increments every 3 days for 35 days. Subjects in the exenatide-naive arm received placebo TID for 35 days. At the end of this 35-day regimen, subjects in both arms received the same highest dose of exenatide (0.24 micro g/kg TID) for 3 days. Thus, the exenatide-naive arm received exenatide for the first time on Day 35. RESULTS: The exenatide-primed arm had a lower proportion of subjects experiencing nausea and vomiting in response to exposure to the highest dose of exenatide (27 vs 56% in the exenatide-naive arm; p = 0.0018). Kaplan-Meier estimates of cumulative incidence were 0.28 in the exenatide-primed arm, compared with 0.68 in the exenatide-naive arm (p

Effect on glycemic control of exenatide (synthetic exendin-4) additive to existing metformin and/or sulfonylurea treatment in patients with type 2 diabetes.

OBJECTIVE: AC2993 (synthetic exendin-4; exenatide) is a peptide that enhances glucose-dependent insulin secretion, suppresses inappropriately elevated glucagon secretion, and slows gastric emptying. AC2993 also promotes beta-cell proliferation and neogenesis in vitro and in animal models. This study examines the activity and safety of subcutaneously injected AC2993 in patients with type 2 diabetes currently treated with diet and/or oral antidiabetic agents (OAAs). RESEARCH DESIGN AND METHODS: A total of 109 patients treated with diet and a sulfonylurea and/or metformin were enrolled in a blinded study. Patients were randomly assigned to one of three subcutaneously (SC) injected regimens of AC2993 (0.08 micro g/kg) or placebo for 28 days. RESULTS: All three AC2993 regimens led to significant reductions in serum fructosamine relative to placebo (P

Pramlintide as an adjunct to insulin therapy improves long-term glycemic and weight control in patients with type 2 diabetes: a 1-year randomized controlled trial.

OBJECTIVE: Mealtime amylin replacement with the human amylin analog pramlintide, as an adjunct to mealtime insulin replacement, reduces postprandial glucose excursions in patients with type 2 diabetes. The aim of the present study was to assess the long-term efficacy and safety of pramlintide in this patient population. RESEARCH DESIGN AND METHODS: In a 52-week, double-blind, placebo-controlled, parallel-group, multicenter study, 656 patients with type 2 diabetes (age 57 +/- 10 years, diabetes duration 12 +/- 7 years, BMI 34.0 +/- 7.0 kg/m(2), HbA(1c) 9.1 +/- 1.2%, mean +/- SD) treated with insulin (alone or in combination with sulfonylureas and/or metformin) were randomized to receive additional preprandial subcutaneous injections of either placebo or pramlintide (60 micro g TID, 90 microg BID, or 120 microg BID). RESULTS: Treatment with pramlintide 120 micro g BID led to a sustained reduction from baseline in HbA(1c) (-0.68 and -0.62% at weeks 26 and 52, respectively), which was significantly greater than that seen with placebo (P < 0.05). The proportion of patients achieving an HbA(1c) <8% was approximately twofold greater with pramlintide (120 microg BID) than with placebo (46 vs. 28%, P < 0.05). The glycemic improvement with pramlintide 120 micro g BID was accompanied by a mean weight loss (-1.4 kg vs. +0.7 kg with placebo at week 52, P < 0.05) and occurred without an overall increase in the severe hypoglycemia event rate. The most common adverse event associated with pramlintide use was transient, mild-to-moderate nausea. CONCLUSIONS: Mealtime amylin replacement with pramlintide 120 microg BID, as an adjunct to insulin therapy, improves long-term glycemic and weight control in patients with type 2 diabetes.