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EXPLORE-Xa A Phase 2, Randomized, Parallel Group, Dose‑Finding, Multicenter, Multinational Study of the Safety, Tolerability and Pilot Efficacy of Three Blinded Doses of the Oral Factor Xa Inhibitor Betrixaban Compared With Open‑Label Dose-Adjusted Warfarin in Patients With Non-Valvular Atrial Fibrillation (EXPLORE-Xa) Steering Committee Stuart J. Connolly, MD, FRCPC Michael D. Ezekowitz, MD, PhD Population Health Research Institute Lankenau Institute for Medical Research McMaster University Thomas Jefferson Medical College Hamilton, Ontario, Canada Wynnewood, Pennsylvania, United States Rafael Diaz, MD Stefan H. Hohnloser, MD, FESC, FACC Dept. of Cardiology and Clinical Research Dept. of Clinical Electrophysiology Instituto Cardiovascular de Rosario Johann Wolfgang Goethe University Rosario, Argentina Frankfurt, Germany Paul Dorian, MD Dept. of Medicine University of Toronto Toronto, Ontario, Canada Study Sponsored by Portola Pharmaceuticals, Inc. and Merck
Disclosures • Michael D. Ezekowitz, MD, PhD • Consultant for Portola and Merck • Received grant support from Portola • Has a sibling employed by Merck
Characteristics of Betrixaban • Orally-active and selective fXa inhibitor • Oral bioavailability 34%, Ki 117 pM • Flat diurnal peak/trough profile • ~20 h PD or “effective” half-life • No dose adjustment expected for renal impairment • Excreted mostly unchanged through bile with minimal renal excretion (<5%) • No major drug interactions expected • Not substrate for CYP450 system • Substrate for efflux proteins including P-glycoprotein • Antidote in development
Study Objectives • Primary Objective • Safety and tolerability of oral betrixaban at doses of 40, 60 and 80 mg once a day compared with dose-adjusted warfarin in patients with non-valvular atrial fibrillation or atrial flutter • Primary Endpoint • Time to major and clinically relevant non-major bleeding • Secondary Endpoints • Time to any bleeding, death, stroke, MI or systemic embolism • Secondary Objective • Pharmacokinetics (PK) and pharmacodynamics (PD) of betrixaban
Inclusion Criteria • Inclusion Criteria • Male or female, age ≥ 18 years. • Women without reproductive potential. • AF at the time of enrollment (randomization) or documented within the last year by Holter, ECG, rhythm strip, pacemaker or other intracardiac recording, resulting in an indication for anticoagulation with warfarin or acenocumerol in the opinion of the treating physician. • One or more of the following risk factors for stroke: • Age 75 years or older • Prior stroke, TIA or systemic (i.e., central nervous system) embolus at least 30 days remote from the time of screening. • Symptomatic congestive heart failure within 3 months or left bentricular dysfunction with an LVEF ≤ 45% by echocardiography, radionuclide study or contrast angiography. • Hypertension requiring pharmacological treatment. • Diabetes. • Age of 55 years or older and previous coronary artery disease or known peripheral artery disease.
Exclusion Criteria Weight less than 40 kg (88 lbs). Need for either hemodialysis or peritoneal dialysis (or likely to require it within one year). AF due to reversible causes. Mechanical prosthetic valve (bioprosthetic valve is allowed) or valvular disease likely to be operated on within one year. Conditions other than AF that require chronic anticoagulation. Persistent, uncontrolled hypertension (SBP > 160 mmHg on repeated measurements). Active infective endocarditis. Scheduled major surgery. Planned pulmonary vein ablation. Recent ischemic stroke, systemic embolic event or acute coronary syndrome within 30 days.
Exclusion Criteria (continued) Severe co-morbid condition with life expectancy of ≤ 1 year. Platelet count < 100,000/mm3. Serum alanine aminotransferase (ALT) or aspirate aminotransferase (AST) > 2.5 times ULN. A history (including family history) of “Long QT Syndrome”. Aspirin > 162 mg daily. Use of verapamil (pending the availability of a drug interaction study with betrixaban). Active alcohol or drug abuse, or psychosocial reasons that make study participation impractical. Use of an investigational drug or device within the past 30 days. Inability to comply with INR monitoring or other protocol-related activities. Unable to give written informed consent.
Patient Disposition and Follow-Up • Minimum follow-up 3 months; Maximum 12 months; Median 147 days
≥ Baseline Characteristics of Patients
Major Bleeding or Clinically Relevant Non-Major Bleeding 3 months minimum f/u
Bleeds at 12 weeks, strokes and deaths + ++ Strokes after 35 days and 54 days on treatment for B60 and B80 respectively + Cardiovascular death (Reported as MI. Not adjudicated as MI per CEC) after 29 days on treatment ++ Cardiovascular death (CHF) after 108 days on treatment
D-Dimer (Change from Baseline) p=0.166* p=0.003* p=0.062* *vs. warfarin (Kruskal-Wallis test)
Conclusions • In the diverse patient population studied there was a dose and concentration dependent effect on the primary endpoint, major and clinically relevant non-major bleeding • Bleeding at 60 and 80 mg comparable to that on warfarin • The number of strokes were within the range expected for warfarin (0-1 per group) • All 3 doses were well tolerated • D-dimer shows activity across dose spectrum with a trend toward a dose response • Larger studies will have to determine the full efficacy and safety of betrixaban
Study Investigators and DSMC Study Investigators* Cossu, Sergio USA Vicari, Ralph M. USA Teixeira, Jose USA O'Dea, Daniel USA Weiss, Robert USA Henderson, David USA Fialkow, Jonathan USA Pesant, Yves Canada Promisloff, Steven USA Gogia, Harinder USA Bakbak, Asaad Canada Goldstein, Mark USA Blonder, Ronald USA Kouz, Simon Canada Ezekowitz, Michael USA Herzog, William USA Teitelbaum, Ivor Canada Bose, Sabyasachi Canada Constance, Christian Canada Bertolet, MD, Barry USA Coutu, Benoit Canada Hotchkiss, David USA O'Hara, Gilles Canada Chodnicki, Dennis USA Boucher, Pierre Jr. Canada Burstein, Jason Canada Gill, Santosh USA Horacek, Thomas Germany Aycock, G. Ramon USA Dorian, Paul Canada Hartmann, Franz Germany Labovtiz, Arthur USA Morillo, Carlos Canada Butter, Christian Germany Rebane, Thomas Canada DSMC members Dr. Alexander Graham G. Turpie (Chairman) Prof. Robin Roberts Dr. Jonathan Halperin Dr. Ken Bauer 16 *By number of patients contributed