Interim analyses and early termination of clinical trials

Enoxaparin Versus Unfractionated Heparin in the Prevention of Venous Thromboembolism After Acute Ischemic Stroke: Rationale, Design, and Methods of an Open-Label, Randomized, Parallel-Group Multicenter Trial

BACKGROUND

Small sample size and methodologic limitations make it difficult to interpret and compare trials of low molecular-weight heparin (for example, enoxaparin) versus unfractionated heparin as prophylactic treatment for venous thromboembolism (VTE), that is, deep vein thrombosis and/or pulmonary embolism, in patients with acute ischemic stroke. This prospective, open-label, randomized, parallel-group, multicenter trial is designed to evaluate the efficacy and safety of enoxaparin versus unfractionated heparin for the prevention of VTE after acute ischemic stroke.

METHODS

Approximately 1760 patients with the diagnosis of acute ischemic stroke accompanied by leg paralysis will be randomly assigned (1:1) within 48 hours of stroke symptoms to receive enoxaparin (40 mg subcutaneously) once daily or unfractionated heparin (5000 U subcutaneously) every 12 hours for 10 +/- 4 days. Contrast venography will be used to evaluate asymptomatic patients after treatment for deep vein thrombosis. In addition, diagnostic algorithms will be used to objectively confirm or rule out VTE events for patients in whom upper- or lower-extremity deep vein thrombosis/pulmonary embolism is suggested.

RESULTS

The primary efficacy end point measure will be the cumulative occurrence of documented VTE during the initial treatment period. Secondary end points are VTE incidence; neurologic outcome at days 30, 60, and 90; safety; and health care resource use during initial hospitalization and during the 30- and 90-day follow-up periods.

CONCLUSIONS

This study will provide clinical and health economic data regarding the use of enoxaparin as primary prophylactic treatment of VTE in patients who have had an acute ischemic stroke.

Efficacy and safety of the monoclonal anti-tumor necrosis factor antibody F(ab′)2 fragment afelimomab in patients with severe sepsis and elevated interleukin-6 levels*

OBJECTIVE

To evaluate whether administration of afelimomab, an anti-tumor necrosis factor F(ab')2 monoclonal antibody fragment, would reduce 28-day all-cause mortality in patients with severe sepsis and elevated serum levels of IL-6.

DESIGN

Prospective, randomized, double-blind, placebo-controlled, multiple-center, phase III clinical trial.

SETTING

One hundred fifty-seven intensive care units in the United States and Canada.

PATIENTS

Subjects were 2,634 patients with severe sepsis secondary to documented infection, of whom 998 had elevated interleukin-6 levels.

INTERVENTIONS

Patients were stratified into two groups by means of a rapid qualitative interleukin-6 test kit designed to identify patients with serum interleukin-6 levels above (test positive) or below (test negative) approximately 1000 pg/mL. Of the 2,634 patients, 998 were stratified into the test-positive group, 1,636 into the test-negative group. They were then randomly assigned 1:1 to receive afelimomab 1 mg/kg or placebo for 3 days and were followed for 28 days. The a priori population for efficacy analysis was the group of patients with elevated baseline interleukin-6 levels as defined by a positive rapid interleukin-6 test result.

MEASUREMENTS AND MAIN RESULTS

In the group of patients with elevated interleukin-6 levels, the mortality rate was 243 of 510 (47.6%) in the placebo group and 213 of 488 (43.6%) in the afelimomab group. Using a logistic regression analysis, treatment with afelimomab was associated with an adjusted reduction in the risk of death of 5.8% (p = .041) and a corresponding reduction of relative risk of death of 11.9%. Mortality rates for the placebo and afelimomab groups in the interleukin-6 test negative population were 234 of 819 (28.6%) and 208 of 817 (25.5%), respectively. In the overall population of interleukin-6 test positive and negative patients, the placebo and afelimomab mortality rates were 477 of 1,329 (35.9%)and 421 of 1,305 (32.2%), respectively. Afelimomab resulted in a significant reduction in tumor necrosis factor and interleukin-6 levels and a more rapid improvement in organ failure scores compared with placebo. The safety profile of afelimomab was similar to that of placebo.

CONCLUSIONS

Afelimomab is safe, biologically active, and well tolerated in patients with severe sepsis, reduces 28-day all-cause mortality, and attenuates the severity of organ dysfunction in patients with elevated interleukin-6 levels.

Interim analyses with delayed observations in clinical trials

The interim analyses based on group sequential procedures are not convenient if the response time relative to the patient accrual rate is long. Since in most trials patients are accrued and randomized continuously, the response data from those already randomized will continue to accumulate when a trial terminates at an interim test. One should analyse all observations received after the trial terminates along with the data that led to the decision to terminate the trial. Although the most likely case is that the combined results are significant, it could happen that the combined results are not significant. We examined the likelihood of such an event. Our study indicated that the O'Brien-Fleming type of group sequential tests with conservative boundaries in the early stages protects from such an unsettling event.

Effects of the bradykinin antagonist Bradycor (deltibant, CP-1027) in severe traumatic brain injury: results of a multi-center, randomized, placebo-controlled trial. American Brain Injury Consortium Study Group

A phase II prospective, randomized, double blind clinical trial of Bradycor, a bradykinin antagonist, was conducted at 31 centers within North America in severely brain injured patients. Patients of Glasgow Coma Score (GCS) 3-8 (n = 139) with at least one reactive pupil were randomized to receive either Bradycor, 3 microg/kg/min or placebo as a continuous intravenous infusion for 5 days, with the infusion beginning within 12 h of the injury. The primary objective was to assess the efficacy of a continuous infusion of Bradycor (3.0 mc/kg/min) in preventing elevation of intracranial pressure (ICP). Other efficacy measures included the effect of Bradycor on the Therapy Intensity Level (TIL), mortality, and functional outcome. A secondary objective was to evaluate the safety of Bradycor in patients with severe brain injury. Randomization was carried out according to a computer generated randomization list. Patients were followed for the first 14 days of hospitalization with long-term outcome assessed at 3 and 6 months after injury. During the infusion and while the ICP monitor was in place, ICP measurements were recorded hourly along with blood pressure and heart rate. A modified version of the TIL was used to record therapeutic interventions hourly, while the ICP was being monitored. Outcome was assessed at 3 and 6 months after injury using the Glasgow Outcome Score (GOS). Bradycor was well tolerated in this patient population, and no adverse events were attributable to the compound. Although positive trends were seen for both ICP and TIL in the Bradycor group, these differences analyzed on a daily basis were not significant. However, a mixed model of variance which included treatment, day, treatment by day interaction, age and GCS revealed that the percentage time ICP of >15 mm Hg on days 4 and 5 was significantly lower in the Bradycor group compared to placebo (p = 0.035). There were fewer deaths in the Bradycor group, which had a 28-day all cause mortality of 20% versus 27% on placebo. Patients treated with Bradycor showed a 10.3% improvement in favorable outcome at 3 months and a 12% improvement in dichotomized GOS at 6 months (p = 0.26). The consistent positive trends seen in ICP, TIL, neuropsychological tests, and, most importantly, 3- and 6-month GOS provide supportive evidence that a bradykinin antagonist may play a neuroprotective role in severe brain injury.