Dabigatran Etexilate (Page 6 of 9)

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Dabigatran was not carcinogenic when administered by oral gavage to mice and rats for up to 2 years. The highest doses tested (200 mg/kg/day) in mice and rats were approximately 3.6 and 6 times, respectively, the human exposure at MRHD of 300 mg/day based on AUC comparisons.
Dabigatran was not mutagenic in in vitro tests, including bacterial reversion tests, mouse lymphoma assay and chromosomal aberration assay in human lymphocytes, and the in vivo micronucleus assay in rats.
In the rat fertility study with oral gavage doses of 15, 70, and 200 mg/kg, males were treated for 29 days prior to mating, during mating up to scheduled termination, and females were treated 15 days prior to mating through gestation Day 6. No adverse effects on male or female fertility were observed at 200 mg/kg or 9 to 12 times the human exposure at MRHD of 300 mg/day based on AUC comparisons. However, the number of implantations decreased in females receiving 70 mg/kg, or 3 times the human exposure at MRHD based on AUC comparisons.

14 CLINICAL STUDIES

14.1 Reduction of Risk of Stroke and Systemic Embolism in Non-valvular Atrial Fibrillation in Adult Patients

The clinical evidence for the efficacy of dabigatran etexilate capsules was derived from RE-LY (Randomized Evaluation of Long-term Anticoagulant Therapy), a multi-center, multi-national, randomized, parallel group trial comparing two blinded doses of dabigatran etexilate capsules (110 mg twice daily and 150 mg twice daily) with open-label warfarin (dosed to target INR of 2 to 3) in patients with non-valvular, persistent, paroxysmal, or permanent atrial fibrillation and one or more of the following additional risk factors:
• Previous stroke, transient ischemic attack (TIA), or systemic embolism
• Left ventricular ejection fraction <40%
• Symptomatic heart failure, ≥ New York Heart Association Class 2
• Age ≥75 years
• Age ≥65 years and one of the following: diabetes mellitus, coronary artery disease (CAD), or hypertension
The primary objective of this study was to determine if dabigatran etexilate capsules were non-inferior to warfarin in reducing the occurrence of the composite endpoint, stroke (ischemic and hemorrhagic) and systemic embolism. The study was designed to ensure that dabigatran etexilate capsules preserved more than 50% of warfarin’s effect as established by previous randomized, placebo-controlled trials of warfarin in atrial fibrillation. Statistical superiority was also analyzed.
A total of 18,113 patients were randomized and followed for a median of 2 years. The patients’ mean age was 71.5 years and the mean CHADS 2 score was 2.1. The patient population was 64% male, 70% Caucasian, 16% Asian, and 1% black. Twenty percent of patients had a history of a stroke or TIA and 50% were Vitamin K antagonist (VKA) naïve, defined as less than 2 months total lifetime exposure to a VKA. Thirty-two percent of the population had never been exposed to a VKA. Concomitant diseases of patients in this trial included hypertension 79%, diabetes 23%, and CAD 28%. At baseline, 40% of patients were on aspirin and 6% were on clopidogrel. For patients randomized to warfarin, the mean percentage of time in therapeutic range (INR 2 to 3) was 64%.
Relative to warfarin and to dabigatran etexilate capsules 110 mg twice daily, dabigatran etexilate capsules 150 mg twice daily significantly reduced the primary composite endpoint of stroke and systemic embolism (see Table 11 and Figure 4).
Table 11 First Occurrence of Stroke or Systemic Embolism in the RE-LY Study *

Dabigatran etexilatecapsules150 mg twice daily Dabigatran etexilatecapsules 110 mg twice daily Warfarin
Patients randomized 6076 6015 6022
Patients (% per yr) with events 135 (1.12%) 183 (1.54%) 203 (1.72%)
Hazard ratio vs. warfarin (95% CI) 0.65 (0.52, 0.81) 0.89 (0.73, 1.09)
P-value for superiority 0.0001 0.27
Hazard ratio vs. dabigatran etexilate capsules110 mg (95% CI) 0.72 (0.58, 0.91)
P-value for superiority 0.005

* Randomized ITT
Figure 4 Kaplan-Meier Curve Estimate of Time to First Stroke or Systemic Embolism

Dabigatrancapfigure4
(click image for full-size original)

The contributions of the components of the composite endpoint, including stroke by subtype, are shown in Table 12. The treatment effect was primarily a reduction in stroke. Dabigatran etexilate capsules 150 mg twice daily was superior in reducing ischemic and hemorrhagic strokes relative to warfarin. Table 12 Strokes and Systemic Embolism in the RE-LY Study

Dabigatran etexilate capsules 150 mg twice daily Warfarin Hazard ratio vs. warfarin (95% CI)
Patients randomized 6076 6022
Stroke 123 187 0.64 (0.51, 0.81)
Ischemicstroke 104 134 0.76 (0.59, 0.98)
Hemorrhagic stroke 12 45 0.26 (0.14, 0.49)
Systemicembolism 13 21 0.61 (0.30, 1.21)

In the RE-LY trial, the rate of all-cause mortality was lower on dabigatran etexilate capsules 150 mg than on warfarin (3.6% per year versus 4.1% per year). The rate of vascular death was lower on dabigatran 150 mg compared to warfarin (2.3% per year versus 2.7% per year). Non-vascular death rates were similar in the treatment arms.
The efficacy of dabigatran etexilate capsules 150 mg twice daily was generally consistent across major subgroups (see Figure 5). Figure 5 Stroke and Systemic Embolism Hazard Ratios by Baseline Characteristics *

dabigatrancapfig5
(click image for full-size original)

* Randomized ITT
Note: The figure above presents effects in various subgroups all of which are baseline characteristics and all of which were pre-specified. The 95% confidence limits that are shown do not take into account how many comparisons were made, nor do they reflect the effect of a particular factor after adjustment for all other factors. Apparent homogeneity or heterogeneity among groups should not be over-interpreted. In RE-LY, a higher rate of clinical myocardial infarction was reported in patients who received dabigatran etexilate capsules (0.7 per 100 patient-years for 150 mg dose) than in those who received warfarin (0.6).

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