Rivaroxaban for Prevention of Thrombotic Events, Hospitalization, and Death in Outpatients With COVID-19: A Randomized Clinical Trial.

BACKGROUND: COVID-19 (coronavirus disease 2019) is associated with heightened risks of venous and arterial thrombosis and hospitalization due to respiratory failure. To assess whether prophylactic anticoagulation can safely reduce the frequency of venous and arterial thrombosis, hospitalization, and death in nonhospitalized patients with symptomatic COVID-19 and at least one thrombosis risk factor, we conducted the PREVENT-HD double-blind, placebo-controlled randomized trial (A Study of Rivaroxaban to Reduce the Risk of Major Venous and Arterial Thrombotic Events, Hospitalization and Death in Medically Ill Outpatients With Acute, Symptomatic COVID-19] Infection). METHODS: PREVENT-HD was conducted between August 2020 and April 2022 at 14 US integrated health care delivery networks. A virtual trial design used remote informed consent and clinical monitoring and facilitated data collection through electronic health record integration with a cloud-based research platform. Nonhospitalized patients with symptomatic COVID-19 and at least one thrombosis risk factor were enrolled and randomly assigned to either 10 mg of oral rivaroxaban or placebo daily for 35 days. The primary efficacy outcome was time to first occurrence of a composite of symptomatic venous thromboembolism, myocardial infarction, ischemic stroke, acute limb ischemia, non-central nervous system systemic arterial embolism, hospitalization, or death through day 35. The principal safety end point was International Society on Thrombosis and Hemostasis critical-site or fatal bleeding. The last study visit was on day 49. RESULTS: The study was terminated prematurely because of enrollment challenges and a lower-than-expected blinded pooled event rate. A total of 1284 patients underwent randomization with complete accrual of primary events through May 2022. No patients were lost to follow-up. The primary efficacy outcome occurred in 22 of 641 in the rivaroxaban group and 19 of 643 in the placebo group (3.4% versus 3.0%; hazard ratio, 1.16 [95% CI, 0.63-2.15]; P=0.63). No patient in either group experienced critical-site or fatal bleeding. One patient receiving rivaroxaban had a major bleed. CONCLUSIONS: The study was terminated prematurely after enrollment of 32% of planned accrual because of recruitment challenges and lower-than-expected event rate. Rivaroxaban prescribed for 35 days in nonhospitalized patients with symptomatic COVID-19 at risk for thrombosis did not appear to reduce a composite end point of venous and arterial thrombotic events, hospitalization, and death. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT04508023.

Association of Bleeding Severity With Mortality in Extended Thromboprophylaxis of Medically Ill Patients in the MAGELLAN and MARINER Trials.

BACKGROUND: Extended thromboprophylaxis has not been widely implemented in acutely ill medical patients because of bleeding concerns. The MAGELLAN (Multicenter, Randomized, Parallel Group Efficacy and Safety Study for the Prevention of Venous Thromboembolism in Hospitalized Medically Ill Patients Comparing Rivaroxaban With Enoxaparin) and MARINER (Medically Ill Patient Assessment of Rivaroxaban Versus Placebo in Reducing Post-Discharge Venous Thrombo-Embolism Risk) trials evaluated whether rivaroxaban compared with enoxaparin or placebo could prevent venous thromboembolism without increased bleeding. We hypothesized that patients with major bleeding but not those with nonmajor clinically relevant bleeding would be at an increased risk of all-cause mortality (ACM). METHODS: We evaluated all bleeding events in patients taking at least 1 dose of study drug and their association with ACM in 4 mutually exclusive groups: (1) no bleeding, or first event was (2) nonmajor clinically relevant bleeding, (3) major bleeding, or (4) trivial bleeding. Using a Cox proportional hazards model adjusted for differences in baseline characteristics associated with ACM, we assessed the risk of ACM after such events. RESULTS: Compared with patients with no bleeding, the risk of ACM for patients with nonmajor clinically relevant bleeding was not increased in MARINER (hazard ratio, 0.43; P=0.235) but was increased in MAGELLAN (hazard ratio, 1.74; P=0.021). Major bleeding was associated with a higher incidence of ACM in both studies, whereas trivial bleeding was not associated with ACM in either study. CONCLUSIONS: Patients with major bleeding had an increased risk of ACM, whereas nonmajor clinically relevant bleeding was not consistently associated with an increased risk of death. These results inform the risk-benefit calculus of extended thromboprophylaxis in medically ill patients. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: MAGELLAN, NCT00571649. URL: https://www. CLINICALTRIALS: gov; Unique identifier: MARINER, NCT02111564.

Rationale and design for the study of rivaroxaban to reduce thrombotic events, hospitalization and death in outpatients with COVID-19: The PREVENT-HD study.

BACKGROUND: COVID-19 is associated with both venous and arterial thrombotic complications. While prophylactic anticoagulation is now widely recommended for hospitalized patients with COVID-19, the effectiveness and safety of thromboprophylaxis in outpatients with COVID-19 has not been established. STUDY DESIGN: PREVENT-HD is a double-blind, placebo-controlled, pragmatic, event-driven phase 3 trial to evaluate the efficacy and safety of rivaroxaban in symptomatic outpatients with laboratory-confirmed COVID-19 at risk for thrombotic events, hospitalization, and death. Several challenges posed by the pandemic have necessitated innovative approaches to clinical trial design, start-up, and conduct. Participants are randomized in a 1:1 ratio, stratified by time from COVID-19 confirmation, to either rivaroxaban 10 mg once daily or placebo for 35 days. The primary efficacy end point is a composite of symptomatic venous thromboembolism, myocardial infarction, ischemic stroke, acute limb ischemia, non-central nervous system systemic embolization, all-cause hospitalization, and all-cause mortality. The primary safety end point is fatal and critical site bleeding according to the International Society on Thrombosis and Haemostasis definition. Enrollment began in August 2020 and is expected to enroll approximately 4,000 participants to yield the required number of end point events. CONCLUSIONS: PREVENT-HD is a pragmatic trial evaluating the efficacy and safety of the direct oral anticoagulant rivaroxaban in the outpatient setting to reduce major venous and arterial thrombotic events, hospitalization, and mortality associated with COVID-19.

Antithrombotic Prophylaxis with Rivaroxaban in Patients with Prehospital COVID-19: A Meta-analysis of Two Placebo-Controlled Trials.

BACKGROUND: We conducted a prespecified meta-analysis of two randomized, placebo-controlled trials of rivaroxaban 10 mg daily in prehospital patients with acute coronavirus disease 2019 (COVID-19). Individually, the trials had limited power to detect a treatment effect due to recruitment stopping ahead of plan. MATERIAL AND METHODS: The statistical analysis plan for the meta-analysis was finalized before unblinding of PREVENT-HD, the larger of the two trials. Pooled risk ratios and pooled risk differences along with the two-sided 95% confidence intervals were calculated using random-effect models. RESULTS: Rivaroxaban did not reduce the occurrence of either the primary prespecified endpoint, a composite of symptomatic arterial and venous thromboembolism, myocardial infarction, ischemic stroke, acute limb ischemia, all-cause hospitalization, and all-cause mortality (risk difference: 0.0044; 95% confidence interval: -0.0263, 0.0175; p = 0.69 for pooled risk difference) or the secondary endpoint of all-cause hospitalization (p = 0.76). Although thrombotic events were infrequent, pooled analysis did reveal that rivaroxaban reduced arterial and venous thrombotic events (placebo 6 events, rivaroxaban 0 events; pooled risk difference: -0.0068; 95% confidence interval: -0.0132, -0.0006; p = 0.03). In the pooled studies, only one major bleeding event was observed in a rivaroxaban-allocated patient with no critical site or fatal bleeding events. CONCLUSION: Although this meta-analysis does not support antithrombotic prophylaxis with rivaroxaban in a broad prehospital population with acute COVID-19, the prevention of arterial and venous thrombotic events among rivaroxaban-allocated patients is consistent with the known thromboprophylactic effect of the drug in medically ill patients.

Identification of an RNA-dependent RNA polymerase in Drosophila involved in RNAi and transposon suppression.

Here, we show that recombinant Drosophila elp1 (D-elp1) produced in Sf9 cells or Escherichia coli, corresponding to the largest of the three subunits in the RNA polymerase II core elongator complex, has RNA-dependent RNA polymerase (RdRP) activity. D-elp1 is a noncanonical RdRP that can synthesize dsRNA from different ssRNA templates using either a primer-dependent or primer-independent initiation mechanism. Of the three core subunits, only D-elp1 depletion inhibits RNAi in S2 cells but does not affect micro RNA function. Furthermore, D-elp1 depletion results in increased steady state levels of representative transposon RNAs and a decrease in the corresponding transposon antisense transcripts and endo siRNAs. In contrast, although Dcr-2 depletion results in increased transposon RNA levels and a reduction in the corresponding endo siRNAs, there is no change in the transposon antisense RNA levels. In D-elp1 null third instar larvae transposon RNA levels are also increased and the corresponding transposon antisense RNAs are reduced. D-elp1 associates tightly with Dcr-2, similar to the Dicer-RdRP interaction observed in lower eukaryotes. These results identify an aspect of the RNAi pathway in Drosophila that suggest transposon derived endo siRNAs, critical for transposon suppression, are produced, in part, in a D-elp1 dependent step that converts transposon RNA into dsRNA that is subsequently processed by Dcr-2. The generality of this mechanism in genome defense and RNA silencing in higher eukaryotes is suggested.

Benefit-Risk Assessment of Rivaroxaban for Extended Thromboprophylaxis After Hospitalization for Medical Illness.

Background Venous thromboembolism (VTE) often occurs after hospitalization in medically ill patients, but the population benefit-risk of extended thromboprophylaxis remains uncertain. Methods and Results The MARINER (Medically Ill Patient Assessment of Rivaroxaban Versus Placebo in Reducing Post-Discharge Venous Thrombo-Embolism Risk) study (NCT02111564) was a randomized double-blind trial that compared thromboprophylaxis with rivaroxaban 10 mg daily versus placebo for 45 days after hospital discharge in medically ill patients with a creatinine clearance ≥50 mL/min. The benefit-risk balance in this population was quantified by calculating the between-treatment rate differences in efficacy and safety end points per 10 000 patients treated. Clinical characteristics of the study population were consistent with a hospitalized medical population at risk for VTE. Treating 10 000 patients with rivaroxaban resulted in 32.5 fewer symptomatic VTE and VTE-related deaths but was associated with 8 additional major bleeding events. The treatment benefit was driven by the prevention of nonfatal symptomatic VTE (26 fewer events). There was no between-treatment difference in the composite of critical site or fatal bleeding. Conclusions Extending thromboprophylaxis with rivaroxaban for 45 days after hospitalization provides a positive benefit-risk balance in medically ill patients at risk for VTE who are not at high risk for bleeding. Registration URL: https://clinicaltrials.gov/; Unique identifier: NCT02111564.

Risk of Severe Bleeding With Extended Rivaroxaban to Prevent Venous Thromboembolism in Acute Medically Ill Patients With Bronchiectasis.

Background: Bronchiectasis is a chronic inflammation of the bronchi with recurrent infections and hemoptysis. The MAGELLAN study compared oral rivaroxaban, 10 mg once daily (QD), for 35 ± 4 days with subcutaneous enoxaparin 40 mg QD for 10 ± 4 days followed by placebo for 25 ± 4 days to prevent venous thromboembolism in patients hospitalized with an acute medical illness. MAGELLAN included a subset of patients with bronchiectasis. In a post hoc analysis, we evaluated the incidence and severity of pulmonary bleeding in patients with bronchiectasis who were hospitalized for an acute medical illness. This analysis included MAGELLAN patients diagnosed with bronchiectasis at baseline. Patients were evaluated by treatment group for International Society on Thrombosis and Haemostasis major bleeding, non-major clinically relevant (NMCR) bleeding, and the composite of the 2 (ie, clinically relevant bleeding). Results: Medically ill patients with bronchiectasis were randomized to rivaroxaban (n = 60) or enoxaparin/placebo (n = 61). There were 2 fatal pulmonary bleeds and 1 fatal gastrointestinal bleed in the rivaroxaban arm and no fatal or major bleeding in the enoxaparin/placebo arm. The incidence of major bleeding was 5% in the rivaroxaban arm. One NMCR bleed occurred in the rivaroxaban arm and 2 NMCR bleeds occurred in the enoxaparin/placebo arm. The incidence of clinically relevant bleeding was 6.7% versus 3.3% in the rivaroxaban and enoxaparin/placebo groups, respectively (relative risk = 2.06 [95% confidence interval: 0.351-12.046]). Conclusion: In-patients hospitalized with bronchiectasis and an acute medical illness, clinically relevant bleeding, including fatal pulmonary hemorrhage, occurs more frequently with extended rivaroxaban thromboprophylaxis than with enoxaparin followed by placebo.

Association Between Asymptomatic Proximal Deep Vein Thrombosis and Mortality in Acutely Ill Medical Patients.

Background Asymptomatic proximal deep vein thrombosis (DVT) is an end point frequently used to evaluate the efficacy of anticoagulant thromboprophylaxis in medical patients. Recently, the clinical relevance of asymptomatic DVT has been challenged. Methods and Results The objective of this study was to evaluate the relationship between asymptomatic proximal DVT and all-cause mortality (ACM) using a cohort analysis of a randomized trial for the prevention of venous thromboembolism (VTE) in acutely ill medical patients. Patients who received at least 1 dose of study drug and had an adequate compression ultrasound examination of the legs on either day 10 or day 35 were categorized into 1 of 3 cohorts: no VTE, asymptomatic proximal DVT, or symptomatic DVT. Cox proportional hazards model, with adjustment for significant independent predictors of mortality, were used to compare the incidences of ACM. Of the 7036 patients, 6776 had no VTE, 236 had asymptomatic DVT, and 24 had symptomatic VTE. The incidence of ACM was 4.8% in patients without VTE. Both asymptomatic proximal DVT (mortality, 11.4%; hazard ratio [HR], 2.31; 95% CI, 1.52-3.51; P<0.0001) and symptomatic VTE (mortality, 29.2%; HR, 9.42; 95% CI, 4.18-21.20; P<0.0001) were independently associated with significant increases in ACM. The analysis was post hoc, and ultrasound results were not available for all patients. Adjustment for baseline variables significantly associated with ACM may not fully compensate for differences. Conclusions Asymptomatic proximal DVT is associated with higher ACM than no VTE and remains a relevant end point to evaluate the efficacy of anticoagulant thromboprophylaxis in medical patients. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT00571649.

Invention of MK-8262, a Cholesteryl Ester Transfer Protein (CETP) Inhibitor Backup to Anacetrapib with Best-in-Class Properties.

Cholesteryl ester transfer protein (CETP) represents one of the key regulators of the homeostasis of lipid particles, including high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles. Epidemiological evidence correlates increased HDL and decreased LDL to coronary heart disease (CHD) risk reduction. This relationship is consistent with a clinical outcomes trial of a CETP inhibitor (anacetrapib) combined with standard of care (statin), which led to a 9% additional risk reduction compared to standard of care alone. We discuss here the discovery of MK-8262, a CETP inhibitor with the potential for being the best-in-class molecule. Novel in vitro and in vivo paradigms were integrated to drug discovery to guide optimization informed by a critical understanding of key clinical adverse effect profiles. We present preclinical and clinical evidence of MK-8262 safety and efficacy by means of HDL increase and LDL reduction as biomarkers for reduced CHD risk.