A Study in Older Subject to Evaluate the Safety and Ability of Andexanet Alfa to Reverse the Anticoagulation Effect of Rivaroxaban

In Part 1, the primary endpoint was percent change from baseline in anti-fXa activity at the nadir, when nadir was defined as the smaller value for anti-fXa activity at the +2 minutes or +5 minutes time point following the end of the bolus. In Part 2, the primary endpoint was the percent change from baseline in anti-fXa activity from its baseline to nadir, when nadir was defined as the smaller value for anti-fXa activity between the 110-minute time point (10 minutes prior to the end of the continuous infusion) and the 5-minute time point after the end of the continuous infusion. The baseline for the primary endpoint in both parts was the anti-fXa activity just prior to administration of andexanet, 4 hours following the Day 4 dose of rivaroxaban. Anti-fXa activity was measured by a modified chromogenic assay.

Time frame: Baseline to +2 minutes or +5 minutes following the end of andexanet/placebo bolus (Part I), or 10 minutes prior to end of andexanet/placebo continuous infusion or 5 minutes after the end of andexanet/placebo continuous infusion (Part II)

Population: Modified Intent-to-Treat Population included all subjects receiving andexanet/placebo with anti-fXa activity baseline value at ≥1 timepoints: 2 or 5 minute after the end of the bolus (Part I; N = 41); 110 minute during continuous infusion, 2 minute before or 5 minute after the end of continuous infusion (Part II; N = 39).

Change from baseline in free rivaroxaban concentration (ng/mL) at the nadir, when nadir was defined as the smaller value for free rivaroxaban at the +2 minute or +5 minute time point after the completion of the andexanet bolus (Part I) or between the 110-minute time point (10 minutes prior to the end of the continuous infusion) and the 5-minute time point after the end of the continuous infusion (inclusive) \[Part II\]. Free plasma concentrations of rivaroxaban was determined using a validated method that involved analysis of citrated human plasma with high-throughput equilibrium dialysis followed by liquid chromatography mass spectrometry.

Time frame: Baseline to +2 minutes or +5 minutes following the end of andexanet/placebo bolus (Part I), or 10 minutes prior to end of andexanet/placebo continuous infusion or 5 minutes after the end of andexanet/placebo continuous infusion (Part II)

Population: 54 subjects who received rivaroxaban were included in the rivaroxaban pharmacokinetics (PK) analysis

Change in ETP from baseline to its peak, where peak was defined as the largest value for ETP between the +2 minute time point and the +10 minute time point after the end of the andexanet bolus (inclusive) {Part I\] or between the 110-minute time point (10 minutes prior to the end of the continuous infusion) and the 5-minute time point after the end of the continuous infusion (inclusive) \[Part II\]. Baseline was the last assessment obtained prior to the first dose of andexanet or placebo. ETP was measured using a tissue factor-initiated thrombin generation assay.

Time frame: Baseline to +2 minutes or +10 minutes following the end of andexanet/placebo bolus (Part I), or 10 minutes prior to end of andexanet/placebo continuous infusion or 5 minutes after the end of andexanet/placebo continuous infusion (Part II)

Population: mITT; 41 and 39 subjects who received andexanet or placebo were included in the PD analysis in Part I and II, respectively.

Number of participants with ≥80% reduction in anti-fXa activity from its baseline to nadir, when nadir was defined as the smaller value for anti-fXa activity at the +2 minute or +5 minute time point after the completion of the andexanet bolus (Part I) or between the 110-minute time point (10 minutes prior to the end of the continuous infusion) and the 5-minute time point after the end of the continuous infusion (inclusive) {Part II\]. Baseline was the last assessment obtained prior to the first dose of andexanet or placebo

Time frame: Baseline to +2 minutes or +5 minutes following the end of andexanet/placebo bolus (Part I), or 10 minutes prior to end of andexanet/placebo continuous infusion or 5 minutes after the end of andexanet/placebo continuous infusion (Part II)

Population: mITT; 41 and 39 subjects who received andexanet or placebo were included in the PD analysis in Part I and II, respectively.

Number of participants with ETP above the lower limit of the normal range at its peak, between the +2 minute time point and the +10 minute time point after the end of the andexanet bolus (inclusive) \[Part I\] or between the 110-minute time point (10 minutes prior to the end of the continuous infusion) and the 5-minute time point after the end of the continuous infusion (inclusive) \[Part II\]. ETP was measured using a tissue factor-initiated thrombin generation assay

Time frame: Baseline to +2 minutes or +10 minutes following the end of andexanet/placebo bolus (Part I), or 10 minutes prior to end of andexanet/placebo continuous infusion or 5 minutes after the end of andexanet/placebo continuous infusion (Part II)

Population: mITT; 41 and 39 subjects who received andexanet or placebo were included in the PD analysis in Part I and II, respectively.

The percent change from baseline in anti-fXa activity at the nadir, following the bolus, when nadir was defined as the smaller value for anti-fXa activity at the +2 minute or +5 minute time point after the completion of the andexanet bolus (Part II). Baseline was the last assessment obtained prior to the first dose of andexanet or placebo

Time frame: Baseline to +2 minutes or +5 minutes following the end of andexanet/placebo bolus (Part II)

Population: mITT; 41 and 39 subjects who received andexanet or placebo were included in the pharmacodynamics (PD) analysis in Part I and II, respectively.