For treatment of acute venous thromboembolism (VTE), dabigatran etexilate was as effective as warfarin with a lower risk of bleeding in two phase III trials, RE-COVER and RE-COVER II. As dabigatran is predominantly renally eliminated, its plasma concentration may be elevated in renally impaired patients, potentially increasing the bleeding risk. Warfarin is primarily metabolized hepatically.
We performed a prespecified subgroup analysis on pooled data from RE-COVER and RE-COVER II to investigate the efficacy and safety of dabigatran versus warfarin according to renal function.
Patients with acute VTE received parenteral anticoagulation and were randomized to the addition of warfarin or warfarin-placebo for at least 5 days until the international normalized ratio (INR) was ≥ 2 at two consecutive measurements. This was followed (on discontinuation of parenteral therapy) by continued warfarin (target INR range 2.0–3.0) or dabigatran 150 mg twice daily (double dummy; “oral only” treatment period) for 6 months. Primary efficacy outcome: recurrent, symptomatic, objectively confirmed VTE or VTE-related death from randomization (i.e., start of parenteral therapy plus either warfarin or warfarin-placebo) up to the end of the prespecified post-treatment follow-up. Safety: major bleeding events (MBEs), the composite of MBEs or clinically relevant bleeding events (CRBEs), and any bleeds, measured from the start of the double-dummy period (treatment with oral dabigatran or warfarin alone) up to the end of the 6-month study period. Thus, the safety analysis excludes events associated with parenteral therapy either in combination with warfarin or with warfarin-placebo prior to commencing dabigatran treatment; it therefore compares dabigatran with warfarin at its full pharmacological potential.
Overall, recurrent VTE or VTE-related death occurred in 68/2553 patients (2.7%) randomized to dabigatran and 62/2554 (2.4%) randomized to warfarin; hazard ratio (HR) 1.09 (95% confidence interval [CI] 0.77, 1.54). Event rates for dabigatran vs warfarin in subgroups with CrCl ≥ 80, 50 to < 80 (mild renal dysfunction), and 30 to < 50 mL/minute (moderate renal dysfunction), respectively, were: 3.1% (58/1860) vs 2.6% (48/1838), 1.9% (10/539) vs 1.6% (9/561), and 0% (0/114) vs 4.1% (5/123). Cox regression analysis showed no statistically significant interaction, indicating similar treatment effects across the CrCL groups. Overall, MBEs were significantly less frequent with dabigatran vs warfarin during the oral treatment only (double-dummy) period (HR 0.60; 95% CI 0.36, 0.99). Results for the respective renal function subgroups are shown in the Table. There was no significant treatment interaction by renal function. MBE/CRBE incidence overall was significantly lower with dabigatran versus warfarin overall (HR 0.56; 95% CI 0.45, 0.71). Renal function subgroup results are shown in the Table. There was no significant treatment interaction by renal function. Similarly, any bleeding events were significantly less frequent with dabigatran than with warfarin overall, and showed no treatment interaction by renal function.
There was no apparent difference in recurrent VTE or VTE-related mortality across renal function groups. Bleeding events increased with declining renal function but were similar or numerically lower with dabigatran than with warfarin. The results suggest no need for dose adjustment of dabigatran in patients with mild or moderate renal dysfunction.
Schulman: Bayer Healthcare: Consultancy, Honoraria, Research Funding; Boehringer Ingelheim: Consultancy, Honoraria, Research Funding. Off Label Use: Dabigatran etexilate is an oral direct thrombin inhibitor approved for the prevention of stroke in patients with atrial fibrillation and (outside the US) for prevention of venous thromboembolism in patients undergoing total hip or knee replacement. This presentation includes discussion of the following off-label use of dabigatran: treatment of venous thromboembolism. Eriksson:Boehringer Ingelheim: Consultancy; BMS: Consultancy; Pfizer: Consultancy. Goldhaber:Portola: Consultancy; Pfizer: Consultancy; Merck: Consultancy; Janssen: Consultancy; BMS: Consultancy, Research Funding; Daiichi: Consultancy, Research Funding; Boehringer Ingelheim: Consultancy; Sanofi-Aventis: Consultancy. Kakkar:Boehringer Ingelheim: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Daiichi: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Eisai: Consultancy, Honoraria, Research Funding. Kearon:Bayer Healthcare Inc: Consultancy; Boehringer Ingelheim (Canada) Ltd./Ltée : Consultancy. Schellong:Daiichi Sankyo: Advisory Boards, Advisory Boards Other, Honoraria; BMS/Pfizer: Honoraria; Bayer Healthcare: Advisory boards, Advisory boards Other, Consultancy, Honoraria; Boehringer Ingelheim: Advisory Boards Other, Consultancy, Honoraria. Feuring:Boehringer Ingelheim: Employment. Peter:Boehringer Ingelheim: Employment. Friedman:Boehringer Ingelheim: Employment.