The Effect of Factor Xa Inhibition, With Rivaroxaban, on the Pathology of Sickle Cell Disease
Phase: PHASE2
Conditions: Sickle Cell Anemia, Sickle Cell-Beta0-Thalassemia
Sponsor: University of North Carolina, Chapel Hill

 
The Effect of Factor Xa Inhibition with Rivaroxaban on the Pathology 
of Sickle Cell Disease 
 
 
 
NCT number NCT02072668 
Document Date 11/20/2015 
 

 
Rivaroxaban in Sickle Cell Disease 
 
The effect of Factor Xa inhibition with Rivaroxaban on the pathology of sickle 
cell disease 
 
Protocol Version Date:  11/20/2015 
Study IND#:  122977 
Principal Investigator 
Kenneth I. Ataga, M.D. 
Division of Hematology/Oncology 
University of North Carolina 
CB# 7305, 170 Manning Drive 
Chapel Hill, NC 27599-7305 
Telephone: (919) 966-0178 
Fax:  (919) 966-6735 
E-mail:  kataga@med.unc.edu 
 
                                                                Co-Investigators 
Nigel S. Key, MD 
Division of Hematology/Oncology 
University of North Carolina 
Chapel Hill, NC 27599-7305 
Telephone: (919) 966-0900 
 
Rupa Redding-Lallinger, MD 
Division of Hematology/Oncology 
University of North Carolina 
Chapel Hill, NC 27599-7305 
Telephone: (919) 966-0900 
 
Jainwen Cai, PhD 
Department of Biostatistics 
University of North Carolina 
Chapel Hill, NC 27599-7305 
Telephone: (919) 966-0900 
 
 
Study Coordinator 
Susan Jones, R.N. 
UNC Comprehensive Sickle Cell Program 
CB# 7305, 170 Manning Drive 
Chapel Hill, NC 27599  
Telephone: (919) 966-6876 

 
Rivaroxaban in Sickle Cell Disease 
 
SYNOPSIS 
Title of the Protocol:  The effect of factor Xa inhibition, with rivaroxaban, on the pathology of 
sickle cell disease 
Overview: As a result of the presence of macrovascular thrombotic complications, as well as the 
biochemical evidence of ongoing coagulation activation, sickle cell disease (SCD) is often 
referred to as a “hypercoagulable state.” SCD is characterized by increased tissue factor 
expression, increased levels of plasma markers of thrombin generation and fibrinolysis, increased 
platelet activation and decreased levels of natural anticoagulant proteins. Despite the abundant 
laboratory evidence of hypercoagulability observed in these patients, it still remains uncertain 
whether the observed coagulation activation contributes to the vascular occlusive episodes that 
characterize SCD. However, recent studies suggest that certain SCD-related complications, 
including thrombotic stroke, may be associated with coagulation activation. In addition, 
inhibition of tissue factor abrogated the activation of coagulation and attenuated inflammation 
and endothelial cell injury as demonstrated by reduced plasma levels of IL-6, serum amyloid P, 
soluble vascular cell adhesion molecule-1 and decreased levels of myeloperoxidase in the lungs 
of sickle cell mice, suggesting a cross-talk between coagulation and inflammation in SCD.   The 
treatment options for SCD remain limited. Although the low molecular weight heparin, 
tinzaparin, has been reported to significantly reduce the duration of acute pain episodes, it remains 
uncertain whether this effect is due to its anticoagulant or anti-adhesive actions. In this study, we 
will evaluate the efficacy and safety of rivaroxaban in SCD. If the data support the hypothesis 
that rivaroxaban is effective and safe in this setting, we plan on carrying out adequately powered 
studies to more definitively evaluate its safety and efficacy in the treatment and/or prevention of 
selected SCD-related complications.  
Intervention: We will conduct a randomized, double-blind, placebo-controlled, crossover trial 
of rivaroxaban (n = 34). After baseline assessments are performed, subjects will receive 
rivaroxaban 20 mg/day or placebo for 4 weeks, separated by a 2 week washout phase. At the end 
of the washout period, a repeat history and examination and laboratory studies will be performed 
which will serve as a baseline for the second treatment phase, and patients will receive either 
rivaroxaban or placebo, depending on their first treatment administration.  
IND Holder:  Kenneth I. Ataga 
Specific Aims:  
A) 
To evaluate the effects of rivaroxaban on plasma markers of coagulation 
activation, inflammation and markers of endothelial cell activation in SCD 
patients during the non-crisis, steady state. 
B) 
To evaluate the effects of rivaroxaban on microvascular blood flow in SCD 
patients during the non-crisis, steady state. 
C) 
To evaluate the safety of rivaroxaban in patients with SCD  
 
Hypotheses/Estimates: Our primary hypothesis is that inhibition of factor Xa with rivaroxaban 
will reduce inflammation, coagulation and endothelial cell activation in patients with SCD.  
  

 
Rivaroxaban in Sickle Cell Disease 
 
Title of the Protocol:  The effect of factor Xa inhibition, with rivaroxaban, on the pathology of 
sickle cell disease 
Criteria for Evaluation:   
Efficacy:  Primary Endpoints: Soluble vascular cell adhesion molecule-1 (VCAM-1) and 
interleukin-6 (IL-6): Plasma levels of soluble VCAM-1 and IL-6 will be obtained at Baseline, 
and then at weeks 2 and 4 during both Treatment Phases. The primary efficacy measure will be 
a comparison of the difference between the measurements following 4 weeks of treatment with 
rivaroxaban/placebo and baseline measurements. 
Exploratory Endpoints: Markers of Coagulation Activation, Endothelial Activation, and 
Inflammation: We will measure plasma levels of markers of coagulation activation (thrombin-
antithrombin [TAT] complexes and D-dimer), other markers of endothelial activation (soluble 
ICAM) and other markers of inflammation (high sensitivity CRP, MPO, IL-2, IL-8, TNFα, 
sPLA2), at Baseline and then at weeks 2 and 4 during the Treatment Phases.   
Microvascular blood flow: We will analyze microvascular blood flow using laser Doppler 
velocimetry (LDV) assessments of post-occlusive reactive hyperemia (PORH). Measurements 
will be obtained at baseline and at 4 weeks during the Treatment Phases. 
Safety Assessment: We will evaluate patients for treatment-related complications for the duration 
of the study. Major bleeding complications (any bleeding episode into critical sites, e.g. 
intracranial bleed, decrease in hemoglobin concentration of at least 2g/dL from baseline or any 
prolonged bleeding that requires a blood transfusion), and other clinically relevant non-major or 
trivial bleeding will be recorded. We will also evaluate for episodes of SCD-related events, 
including acute pain episodes during scheduled follow up visits  
Study Design:  This is a randomized, double-blind, placebo-controlled, crossover study of 
rivaroxaban to evaluate the efficacy and safety of rivaroxaban in SCD. It will be divided into 
a Screening/Baseline phase, Treatment phase, and Follow-up phase. 
Study Population: Thirty two patients with SCD (HbSS or HbSβ0 thalassemia) between the 
ages of 18 and 65 who meet the eligibility criteria and provide consent to participate in the 
study, will be randomized in this crossover trial. 
 
Clinical and Laboratory Evaluations:  The Screening/Baseline Phase will occur within 28 
days of study drug administration and will include: informed consent, a history and physical 
examination, and clinical laboratory tests including: a complete blood count, routine 
coagulation studies, routine chemistries to assess liver and renal function chest x-ray, brain 
MRI/MRA scan and serum or urine pregnancy test (if female, and of child-bearing capacity). 
During the Treatment Phase, we will also obtain a complete blood count, routine chemistries 
to assess liver and renal function, and pregnancy test (if female); and prior to the second 
treatment phase, a repeat history and examination and laboratory studies will be performed, 
which will serve as a baseline for the second treatment phase.  Finally, measurements of 
microvascular blood flow (assessed non-invasively using laser Doppler velocimetry), 
endothelial activation (soluble VCAM, soluble ICAM), coagulation activation (TAT and D-
dimer) and markers of inflammation (IL-6, high sensitivity CRP, MPO, IL-2, IL-8, TNFα, 
sPLA2) will be obtained at specified time points during the Baseline, Treatment and 
Washout/Follow-up Phases. The Follow-up Phase will consist of safety assessments 
performed four weeks after the final dose of study treatment. 

 
Rivaroxaban in Sickle Cell Disease 
 
Title of the Protocol:  The effect of factor Xa inhibition, with rivaroxaban, on the pathology of 
sickle cell disease 
Sample Size: In a 2x2 crossover design, assuming a correlation of 0.65 for the pre- and post-
treatment measures, to detect a difference of 0.245 in the change of log(sVCAM) and 0.475 in 
the change of log(IL-6) between the rivaroxaban and placebo groups requires a minimum 
sample size of 15 per sequence (a total sample size of 30) at 80% power and α =0.05. Assuming 
a 10% dropout rate, a total of 34 patients is required for this study (17 in each sequence). 
Randomization:  1:1 randomization to receive rivaroxaban or placebo. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Rivaroxaban in Sickle Cell Disease 
 
BACKGROUND, SIGNIFICANCE AND RATIONALE   
Sickle cell disease (SCD) affects approximately 100, 000 individuals in the United States. The 
polymerization of deoxygenated sickle hemoglobin is the primary event in the pathogenesis of 
SCD {Bunn HF, 1997}.  SCD is also associated with additional pathologic processes, including 
inflammation, increased oxidative stress, endothelial activation and dysfunction, stasis, 
reperfusion injury and activation of coagulation. These processes are highly interconnected and 
contribute to the complex pathophysiology of SCD{Frenette, 2007; Hebbel, 2009}.  
The coagulation cascade can be divided into the extrinsic, intrinsic and common pathways 
{Mackman, 2007}. The extrinsic pathway consists of the transmembrane receptor tissue factor 
(TF) and plasma factor VII/VIIa (FVII/FVIIa). TF binds FVII/FVIIa with a high affinity and 
forms a TF:FVIIa complex that activates FX. The intrinsic pathway is an alternative way to 
activate coagulation via FXIIa and FXIa. It amplifies the generation of FXa via the FVIIIa/FIXa 
intrinsic tenase complex. Finally, the common pathway consists of the proteases, FXa and 
thrombin which cleaves fibrinogen to fibrin. Importantly, coagulation and inflammation are 
interconnected in many diseases and protease activated receptors (PARs) mediate this cross-talk 
{Mackman, 2007}. PAR-1 is activated by various proteases, including thrombin and FXa, whereas 
PAR-2 is activated by FXa and FVIIa as well as other proteases {Coughlin, 2000}{Riewald, 
2001}{Camerer, 2000}{Rao, 2005}. Patients with SCD demonstrate elevated levels of whole 
blood TF procoagulant activity that correlates with increased expression of TF antigen on 
monocytes {Key, 1998; Setty,  }. Furthermore, we and others have shown that these patients have 
increased plasma levels of various markers of activation of coagulation, such as thrombin-
antithrombin complexes (TAT), prothrombin fragment F1.2 (F1.2) and D-dimers {Ataga, 2007}. 
In mouse models of SCD, TF expression is increased in the endothelium of the lung 
microvasculature and in circulating monocytes {Solovey, 2004}.In addition, TF expression is 
increased by hypoxia/re-oxygenation {Solovey, 2004}.  
Despite the fact that SCD patients are hypercoagulable, little is known about the contribution of 
coagulation to the pathology of SCD. Thrombosis appears to play an important role in certain 
complications of SCD. Large vessel narrowing with superimposed thrombosis is the most 
common cause of thrombotic stroke in SCD patients. Our recent observation of the association 
between D-dimer levels and a history of stroke suggests that coagulation activation may contribute 
to the pathophysiology of thrombotic stroke in SCD {Ataga, 2012}.  Both old and new thrombi 
are found in the pulmonary vasculature of patients with lung disease (2) and an in-situ thrombotic 
arteriopathy is observed in patients with PHT. Furthermore, published retrospective studies based 
on discharge diagnoses suggest that both pulmonary embolism and pregnancy-related venous 
thromboembolism appear to occur more commonly in SCD patients than in appropriate control 
patients {Novelli et al}. 
Several clinical studies have analyzed the effect of different anticoagulants, including warfarin, 
heparin or acenocoumarol, on acute pain crisis in sickle cell patients. These studies have 
demonstrated modest effects at best {Ataga, 2007}. However, most of these studies were 
performed on small numbers of patients and used pain crisis as the only clinical endpoint. Notably, 
the only adequately powered, appropriately designed (i.e. placebo-controlled) study to examine the 
effect of anticoagulation (low molecular weight heparin, tinzaparin, for 7 days) in SCD showed a 
positive result, with a reduction in the duration of pain crisis and hospital stay{Qari, 2007}. 
However, it remains uncertain whether the observed clinical effect is due to the anticoagulant or 
anti-adhesive action of the drug. We contend that the contribution of the hypercoagulable state to 

 
Rivaroxaban in Sickle Cell Disease 
 
the pathophysiology of SCD has yet to be investigated adequately in clinical studies using new 
anticoagulant agents.  
Hypothesis: Inhibition of FXa will reduce coagulation, inflammation, and endothelial cell 
activation and improve microvascular blood flow in patients with SCD.  We will perform a 
proof-of-concept study using the FXa inhibitor, rivaxoxaban, to: (i) evaluate the effects of 
rivaroxaban on coagulation, inflammation and markers of EC activation in SCD patients during 
the non-crisis, steady state; (ii) determine the effects of rivaroxaban on microvascular blood flow 
in SCD patients during the non-crisis, steady state; and (iii) assess the safety of rivaroxaban in 
patients with SCD. 
Rivaxoxaban 
Rivaroxaban is an oral direct factor Xa inhibitor that selectively blocks the active site of factor 
Xa. In addition, it inhibits prothrombinase activity, clot-associated factor Xa, and thrombin 
generation. This mechanism is unique to small, direct inhibitors because factor Xa that is 
incorporated in the prothrombinase complex is protected from inhibition by antithrombin and by 
antithrombin-dependent anticoagulants.  Rivaroxaban is metabolized in the liver through 
oxidative and hydrolytic processes catalyzed by cytochrome P450 (CYP) 3A4/5 and 2J2. It is 
also a substrate for the P-glycoprotein efflux transporter protein. Approximately 66% of 
rivaroxaban is excreted in the kidneys (36% as unchanged drug), and the remainder is excreted in 
the feces as unchanged drug. In healthy, white men between 19 and 45 years, the administration 
of a single dose of rivaroxaban (5 to 80 mg) resulted in a maximum factor Xa inhibition of 20% 
to 80% within 1 to 4 hours after administration. After administration of the drug, maximum 
concentration was attained in 2 hours and the half-life was between 6 and 7 hours. Rivaroxaban 
prolonged the prothrombin time, activated partial thromboplastin time, and HepTest (a low-
molecular-weight heparin [LMWH] activity assay), but had no effect on thrombin or 
antithrombin activity. In a study with multiple doses of rivaroxaban (5 mg once or twice daily to 
30 mg twice daily) administered to healthy men aged 20 to 45 years, the maximum concentration 
was reached in 2 to 4 hours and maximum factor Xa inhibition ranged from 22% (5-mg dose) to 
68% (30-mg dose). Based on data from a multiple-dose study, rivaroxaban has predictable, dose-
proportional pharmacokinetic and pharmacodynamic properties. The AUC of rivaroxaban is 
increased by 50% and the half-life prolonged to between 11 and 13 hours in elderly patients 
compared with younger patients.  
Moderate renal impairment (creatinine clearance [CrCl] of 30–49 mL/min) and increased age 
lead to slight increases in rivaroxaban exposure. A rivaroxaban dose of 15 mg daily in patients 
with CrCl of 30 to 49 mL/min achieves a maximum concentration similar to that observed with a 
dose of 20 mg daily in patients with normal renal function. The increases in the AUC of 
inhibition of factor Xa activity are 50%, 86%, and 100% for mild, moderate, and severe renal 
impairment, respectively. In patients being treated for nonvalvular atrial fibrillation, it is 
recommended to reduce the dose of rivaroxaban to 15 mg once daily if the CrCl is 15 to 50 
mL/min. It is recommended that the use of rivaroxaban be avoided in patients with moderate 
(Child-Pugh B) and severe (Child-Pugh C) hepatic impairment or with any hepatic disease 
associated with a coagulopathy.  Drugs that are combined p-glycoprotein and CYP3A4 
inhibitors, including “azole” antifungals and HIV protease inhibitors, result in increases in 
rivaroxaban exposure and factor Xa inhibition. Drugs that are combined p-glycoprotein inducers 
and strong CYP3A4 inducers such as rifampicin (which cause 50% and 22% decreases in AUC 
and maximum concentration, respectively), phenytoin, carbamazepine, and St. John's wort 

 
Rivaroxaban in Sickle Cell Disease 
 
should also be avoided with rivaroxaban administration. The pharmacokinetic and 
pharmacodynamic properties of rivaroxaban are not affected by the co-administration of aspirin, 
naproxen, ranitidine, omeprazole, or aluminum-magnesium hydroxide. Rivaroxaban exposure is 
reported to be lower after meals and the presence of food delayed the time to maximum 
concentration, but increased both the maximum plasma concentration and AUC at doses greater 
than 10 mg. It is recommended to take 15- and 20-mg tablets of rivaroxaban with the evening 
meal. The absolute bioavailability of the 10 mg rivaroxaban tablet is not affected by food and 
this dose can be taken either with or without food.  
The RECORD (Regulation of Coagulation in Orthopedic Surgery to Prevent Deep Venous 
Thrombosis and Pulmonary Embolism) trials evaluated the efficacy and tolerability of 
rivaroxaban for venous thromboembolism (VTE) prophylaxis after elective total hip and total 
knee replacements. RECORD 1 compared the rates of VTE and death for rivaroxaban 10 mg 
given orally once daily for 35 days to enoxaparin 40 mg given subcutaneously once daily for 35 
days after elective total hip arthroplasty (THA). The primary efficacy outcome (composite of any 
DVT, nonfatal pulmonary embolism, or death from any cause up to 36 days after the procedure) 
occurred in 0.8% of patients treated with rivaroxaban [13/1537] vs. 3.4 % of patients treated with 
enoxaparin [50/1492] in the per-protocol population [absolute risk reduction (ARR), 2.6%; 95% 
CI, 1.5%–3.6%]), which met the pre-specified non-inferiority requirements. Rivaroxaban was 
superior to enoxaparin in the modified intent-to-treat group, with 1.1% (18/1595) of rivaroxaban 
treated patients having 1 of the primary efficacy events compared with 3.7% (58/1558) of 
enoxaparin-treated patients (ARR, 2.6%; 95% CI, 1.5%–3.7%). Six of 2209 patients (0.3%) 
assigned to receive rivaroxaban compared with 2 of 2224 patients (0.1%) assigned to receive 
enoxaparin had a major bleeding event during the on-treatment follow-up (p = 0.18), although 
one of the 6 bleeding events in the rivaroxaban group occurred during the procedure and before 
the patient received the first dose of drug. The rate of clinically relevant bleeding appeared to be 
higher in the rivaroxaban group (2.9% vs 2.4%), as was the combination of major and clinically 
relevant bleeding (3.2% vs 2.5%). The rates of non–bleeding-related adverse events were similar, 
and there was no difference in the prevalence of liver enzyme elevations. With extended 
anticoagulation therapy (31–39 days) with rivaroxaban and shorter-duration anticoagulation 
therapy (10–14 days) with enoxaparin (RECORD 2),  there were fewer VTE and deaths after 
elective total hip arthroplasty in the extended duration anticoagulation group (i.e, rivaroxaban 10 
mg administered orally once daily for a mean of 33–34 days) (2.0% [17/864]) compared with 
that in the shorter-duration anticoagulation group (ie, enoxaparin 40 mg administered 
subcutaneously once daily for a mean of 12–13 days) (9.3% [81/869]) (AAR, 7.4%, 95% CI, 
5.2–9.4; P < 0.0001). The incidence of major bleeding was similar between both treatment 2 
groups, but there were more cases of non-major bleeding events (6.5% vs. 5.5%) and clinically 
relevant bleeding (3.3% vs 2.7%) in the rivaroxaban group. Serious, non–bleeding-related 
adverse event rates were similar between the 2 treatment groups (1.1% with rivaroxaban vs 1.4% 
with enoxaparin) as were rates of ALT elevations >3 × ULN (0.5% with rivaroxaban vs. 0.6% 
with enoxaparin). RECORD 3 demonstrated that a 10- to 14-day course of rivaroxaban 10 mg 
daily after elective total knee replacement provided a greater reduction in risk for the composite 
efficacy outcome (defined as DVT, PE, or death occurring 13–17 days after surgery) than the 
equivalent duration of enoxaparin 40 mg given subcutaneously once daily (9.6% [79/824] vs 
18.9% [166/878]; P < 0.001). As in RECORD 1 and RECORD 2, there was no difference 
between the 2 treatment groups in major bleeding rates (0.6% and 0.5% for rivaroxaban and 
enoxaparin, respectively; P = 0.77). However, the rate of clinically relevant, non-major bleeding 

 
Rivaroxaban in Sickle Cell Disease 
 
was higher in the rivaroxaban arm (2.7%) compared with the rate in the enoxaparin-treated group 
(2.3%). In addition, drug-related adverse event rates were similar (12% with rivaroxaban vs. 
13% with enoxaparin). In the RECORD 4 trial, a 10 to 14-day duration of rivaroxaban 10 mg 
given orally once daily was found to be non-inferior to a similar duration of enoxaparin 30 mg 
given subcutaneously every 12 hours in the intent-to-treat population (6.9% [67/965] vs. 10.1% 
[97/959]; ARR, 3.19%; 95% CI, 0.71–5.67; P = 0.0118) and superior to enoxaparin in the per-
protocol population (6.7% [58/864] vs. 9.3% [82/878]; AAR, 2.71%; 95% CI, 0.17–5.25; P = 
0.0362) after elective total knee replacement. There were no significant differences in major 
bleeding events (0.7% [10/1526] vs 0.5% [4/1508]; P = 0.1096) between rivaroxaban and 
enoxaparin, although p values were not reported for clinically relevant, non-major bleeding 
events (2.6% vs 2.0%) and drug-related adverse events (20.3% vs 19.6%).  In a pooled analysis 
of the RECORD 1 to 4 trials, the primary outcome of the composite of symptomatic VTE and 
all-cause mortality occurred in 29/6183 (0.5%) of rivaroxaban-treated patients and 60/6200 
(1.0%) in enoxaparin-treated patients (odds ratio [OR], 0.48; 95% CI, 0.30–0.76; P = 0.001). 
There were numerically more bleeding events in the 6183 rivaroxaban-treated patients compared 
with the 6200 enoxaparin-treated patients, but the differences were not statistically significant.  
A meta-analysis of 8 randomized control trials of 15,586 patients who underwent elective total 
hip arthroplasty and total knee replacement showed that rivaroxaban lowered VTE events and 
all-cause mortality by an additional 44% (relative risk [RR], 0.56; 95% CI, 0.39–0.80) compared 
with enoxaparin, without a statistically significant difference in major or clinically relevant 
bleeding.  
The ROCKET-AF (Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with 
Vitamin K Antagonism for Prevention of Stroke and Embolism) trial was a double-blind study 
that compared rivaroxaban 20 mg daily with warfarin (international normalized ratio [INR], 2.0 
– 3.0). In the intent-to-treat group, 2.1% of rivaroxaban-treated patients versus 2.4% of warfarin-
treated patients experienced a primary event (HR, 0.88; 95% CI, 0.74–1.03; P < 0.001 for 
noninferiority, P = 0.12 for superiority). There was no difference in the prevalence of major and 
clinically relevant non-major bleeding or major bleeding. Rivaroxaban was associated with 
significantly decreased incidence of intracranial hemorrhage (0.5% vs 0.7% per year; HR, 0.67; 
95% CI, 0.47–0.93; P = 0.02), whereas the frequency of major gastrointestinal bleeding was 
more common in rivaroxaban-treated patients (3.2% vs 2.2%; absolute increase 1%; P < 0.001).  
The EINSTEIN program provides efficacy and tolerability data for rivaroxaban use for VTE 
treatment. The EINSTEIN program consists of 3 randomized trials: the acute DVT treatment trial, 
the acute PE trial, and the study of extended-duration treatment for DVT and PE.  Rivaroxaban 
was non-inferior to standard therapy with 36 of the 1731 patients (2.1%) in the rivaroxaban group 
and 51 of the 1718 patients (3.0%) having a confirmed recurrence of symptomatic VTE (defined 
as the composite of DVT and fatal or non-fatal PE) (HR, 0.68; 95% CI, 0.44–1.04; P < 0.001 for 
non-inferiority). The prevalence of the tolerability outcome was similar, with 8.1% of patients in 
both arms having a major or non-major, clinically relevant bleeding event (HR, 0.97; 95% CI, 
0.76–1.22; P = 0.77). Numerically there were fewer major bleeding events in the rivaroxaban 
group, but this difference was not statistically significant (0.8% vs 1.2%; HR, 0.65; 95% CI, 0.33–
1.30; P = 0.21). Overall, the rate of adverse clinical events, defined as the occurrence of a VTE or 
major bleeding event, was lower in the rivaroxaban treatment group (2.9% vs 4.2%; HR, 0.67; 
95% CI, 0.47–0.85). The EINSTEIN-PE results showed rivaroxaban to be non-inferior to standard 
treatment in reducing the risk for recurrent VTE (2.1% [50/2419] for rivaroxaban vs. 1.8% 
[44/2413] for standard therapy; HR, 1.12; 95% CI, 0.75–1.68; P = 0.003). Moreover, the 

 
Rivaroxaban in Sickle Cell Disease 
 
occurrence of the principal tolerability outcome was similar between the 2 treatment groups 
(10.3% [249/2419] with rivaroxaban vs 11.4% [274/2413] with standard therapy; HR, 0.90; 95% 
CI, 0.76–1.07; P = 0.23). There were fewer major bleeding events in the rivaroxaban arm (1.1% vs 
2.2%; HR, 0.49; 95% CI, 0.31–0.79; P = 0.003) and the rates of non-bleeding adverse events were 
similar in the 2 treatment groups. The EINSTEIN Continued Treatment Study aimed to determine 
the potential benefits of prolonging anticoagulant therapy by using rivaroxaban for an additional 6 
to 12 months. This double-blind, placebo-controlled, superiority study showed that an additional 6 
to 12 months of anticoagulation with rivaroxaban resulted in an 82% reduction in VTE recurrence 
(1.3% [8/602] with rivaroxaban vs. 7.1% [42/594] with placebo; HR, 0.18, 95% CI, 0.09–0.39; P 
< 0.001), but also caused a 5-fold increase in major and clinically relevant non-major bleeding 
events (6% [36/598] with rivaroxaban vs 1.2% [7/590] with placebo; HR, 5.19, 95% CI, 2.3–11.7; 
P < 0.001). There were 4 major bleeding events in the rivaroxaban group and none in the placebo 
group (P = 0.11). 
PRELIMINARY DATA 
Inhibition of TF reduces inflammation in BERKBM and TWSS mice.  
We analyzed plasma levels of various cytokines and chemokines (GM-CSF, IFN-γ, IL-10, IL-
12p70, IL-13, IL-17, IL-1α, IL-2, IL-4, IL-5, IL-6, MCP-1, KC, MIP-2, TNF-α and VEGF) in 
sickle cell mice using a multiplex cytokine assay. Interestingly, IL-6 was the only cytokine that 
was significantly increased in both BERK mice or BERKBM compared to controls (data not 
shown). The elevated level of IL-6 in BERK or BERKBM mice was confirmed by ELISA. In 
addition, BERK mice also demonstrated increased plasma levels of IL-18 (not shown). We also 
found that BERK mice had elevated plasma levels of sVCAM-1, sICAM-1 and sE-selectin, 
which are markers of endothelial injury, as well as serum amyloid protein (SAP), which is a 
major acute phase protein in mice.  To determine if TF contributes to the inflammatory response 
in SCD, these inflammatory markers were measured in WTBM and BERKBM mice that were 
treated with either a rat anti-mouse TF monoclonal inhibitory antibody, 1H1 or control IgG. 
Inhibition of TF significantly reduced plasma levels of IL-6, SAP and sVCAM-1 but did not 
attenuate the increased plasma levels of IL-18, sICAM-1 and sE-selectin. Similar effects were 
observed in Townes mice treated with the anti-TF antibody. 
Blocking TF attenuates neutrophil infiltration/activation into the lungs of BERKBM mice. 
In SCD, chronic ischemia leads to pathological changes in multiple organs, including the lung, 
liver and kidney{Paszty, 1997}. Recent studies have demonstrated that neutrophils contribute to 
these proceses {Polanowska-Grabowska,; Wallace, 2009}. We observed infiltration of 
neutrophils in the lungs and livers but not kidneys of BERK mice compared to WT controls. 
Consistent with this observation, levels of MPO, a marker of neutrophil activation, were also 
increased in the lungs and livers of BERK and BERKBM mice.  Interestingly, 1H1 significantly 
reduced levels of MPO in the lungs but not livers in BERKBM mice. Furthermore, increased 
levels of MPO in lung and liver were associated with increased expression of the chemokines 
MCP-1 and KC in BERKBM mice compared to WTBM mice. Here again, 1H1 treatment 
significantly attenuated expression of both chemokines in the lung but not in the liver. The high 
level of TF in the lung compared to the liver may explain these different results (data not shown). 
Endothelial cell-specific deletion of TF has no effect on activation of coagulation but reduces 
plasma levels of IL-6 in sickle cell mice. 

 
Rivaroxaban in Sickle Cell Disease 
 
To investigate the role of TF expressed by ECs in the activation of coagulation in a mouse model 
of SCD, we generated sickle mice with an EC-specific deletion of the TF gene. We have recently 
demonstrated that TFflox/flox,Tie-2 Cre+ mice have almost complete deletion of the TF gene in 
both lung EC and hematopoietic cells{Pawlinski, 2012}. To generate sickle and control mice 
with EC-specific deletion of TF and normal TF expression in hematopoietic cells, we 
transplanted these mice with bone marrow from BERK or WT mice.  TFflox/flox mice were used as 
controls. Interestingly, deletion of TF in ECs did not affect plasma TAT levels but significantly 
reduced IL-6 levels. However, the increased plasma levels of IL-18, SAP and markers of EC 
activation, as well as increased levels of MPO in the lung and liver, were not affected by EC-
specific deletion of TF in sickle cell mice. These data indicate that EC TF contributes only to IL-
6 expression, whereas other cellular sources of TF contribute to inflammation and EC activation.  
Contribution of PAR-1 and PAR-2 expressed on non-hematopoietic cells to the pathology of 
SCD.  
We hypothesized that TF-dependent generation of coagulation proteases contributes to 
inflammation and EC activation by activation of PAR-1 and PAR-2. To generate sickle cell mice 
lacking PAR-1 or PAR-2 expression in all non-hematopoietic cells, we transplanted PAR-1-/- or 
PAR-2-/- mice with bone marrow from sickle cell mice. PAR-1 deficiency in non-hematopoietic 
cells significantly reduced plasma levels of sVCAM-1 but not IL-6 or SAP. In contrast, PAR-2 
deficiency in non-hematopoietic cells had no effect on plasma levels of sVCAM-1 but 
significantly reduced plasma levels of IL-6 and SAP. These data indicate that PAR-1 signaling 
contributes to endothelial cell activation whereas PAR-2 promotes inflammation in sickle cell 
mice.   
Inhibition of thrombin does not decrease endothelial cell activation or inflammation.  
Next, we investigated the effect of thrombin inhibition with dabigatran treatment on activation of 
coagulation, inflammation and endothelial cell activation in sickle cell mice. We fed mice a 
chow containing 10 mg of dabigatran per gram of food.   Plasma levels of dabigatran in these 
anticoagulated mice are similar to the levels observed in humans receiving a dose of dabigatran 
of 150 mg bid (J. Van Ryn, unpublished data). Inhibition of thrombin with dabigatran 
significantly increased aPTT (from 26.6±1.2 to 76.2±8.5) in WT and from 25.1±1.3 to 70.1±10.7 
seconds in BERK mice) and reduced plasma TAT levels in sickle cell mice. However, thrombin 
inhibition had no effect on plasma levels of IL-6, SAP or sVCAM-1. These data suggest either 
the dose of dabigatran used is insufficient to block local thrombin activation of PAR-1 or other 
proteases are activating PAR-1 in the mice. This result strongly suggests that inhibition of the 
clotting system upstream of thrombin, i.e. at TF:FVIa, FXa or FXIa, is more likely to reduce 
inflammation and EC activation.   
Inhibition of FXIa reduces plasma TAT levels in sickle cell mice. 
To determine if the intrinsic coagulation pathway contributes to the hypercoagulable state in 
SCD, we treated sickle cell mice with an antibody called 14E11 (kindly provided by Dr. A. 
Gruber) that blocks activation of the intrinsic coagulation pathway by inhibiting FXIa 
generation. We observed that 24 hours after injection of 14E11 (4 mg/kg) the aPTT was 
significantly increased and plasma TAT was significantly reduced in BERK mice. We did not 
measure other parameters due to the short time period of this experiment (1 day). The 
mechanism of FXIa activation is not known and will not be pursued in this proposal. It is 
possible that polyphosphates released from activated platelets may activate FXII {Smith, 
2006}{Muller, 2009}. 

 
Rivaroxaban in Sickle Cell Disease 
 
Measurements of coagulation activation, EC activation and cytokine expression in sickle cell 
patients. 
Our group has had a long-term interest in coagulation activation in patients with SCD{Ataga, 
2008 #292; Ataga, 2007 #272; Key, 1998 #269}. In a study of 76 patients with SCD and 6 
healthy, control subjects of African descent, SCD patients had significantly higher D-dimer 
levels than control subjects (1251.5 ng/mL [FEU] vs. 318 ng/mL [FEU]; p = 0.02) {Ataga, 
2008}. The median values of TAT and F1+2 levels were also higher in SCD patients, although 
the differences were not statistically significant.  
In another study of 64 SCD patients, we observed a 
correlation between TAT and lactate dehydrogenase (r = 
0.57, p < 0.0001) (Figure 1A), with borderline correlations 
between TAT and total bilirubin (r = 0.25; p = 0.054), 
indirect bilirubin (r = 0.26, p = 0.051), and hemoglobin (r = 
- 0.24; p = 0.071) {Ataga, 2012}. TAT was also correlated 
with the absolute monocyte count (r = 0.27; p = 0.035) and 
NT-proBNP (r = 0.35; p = 0.005). Similarly, D-dimer was 
correlated with lactate dehydrogenase (r = 0.56; p < 0.0001) 
(Figure 1B), indirect bilirubin (r = 0.26; p = 0.048), 
hemoglobin (r = - 0.32; p= 0.012), NT proBNP (r = 0.42; p 
< 0.0001), with borderline correlations with absolute 
monocyte count (r = 0.23; p = 0.074). Both TAT (r = 0.37; 
p = 0.004) and D-dimer (r = 0.49; p < 0.0001) (Figure 2) 
were correlated with soluble VCAM-1. When the analyses 
were limited to only patients with SS/SD/Sβ0 thalassemia, 
there was a significant correlation between TAT and lactate 
dehydrogenase (r = 0.62, p < 0.0001), indirect bilirubin (r = 
0.296, p = 0.044), and NT-proBNP (r = 0.32, p = 0.026), 
with borderline correlation with total bilirubin (r = 0.28, p = 
0.053) and absolute monocyte count (r = 0.25, p = 0.089). 
Similarly, we observed significant correlations between D-
dimer and lactate dehydrogenase (r = 0.60, p < 0.0001), 
hemoglobin (r = - 0.29, p = 0.039), and fetal hemoglobin (r 
= - 0.31, p = 0.035), NT-proBNP (r = 0.49, p < 0.0001), 
with borderline correlations with platelet count (r = - 0.28, p 
= 0.053), total bilirubin (r = 0.24, p = 0.093) and indirect bilirubin (r = 0.26, p = 0.07).  
Finally, we observed a significant correlation between TAT and D-dimer (r = 0.66; 
p<0.0001) (Figure 3). However, no correlations were observed between TAT and soluble 
CD40 ligand (r = 0.016, p = 0.91) or between TAT and MPTF procoagulant activity (r = 
0.064, p = 0.63). Similarly, no correlations were observed between D-dimer and soluble 
CD40 ligand (r = −0.17; p = 0.19) or between D-dimer and MPTF procoagulant activity (r = 
0.11, p = 0.40). 
 
1A
 
1B
 

 
Rivaroxaban in Sickle Cell Disease 
 
 
 
 
 
 
 
 
 
 
 
Plasma markers of coagulation activation are associated with clinical complications in 
SCD. 
The level of TAT was significantly higher in patients with a history of retinopathy compared 
to those without this complication (6.05 ng/L; IQR, 4.91, 10.98 ng/L vs. 4.52 ng/L; IQR, 
3.22, 7.33 ng/L, p= 0.023). In addition, the level of TAT was lower in patients on 
hydroxyurea therapy compared to those not on such therapy (4.39 ng/L; IQR, 3.25, 8.77 
ng/L vs. 6.5 ng/L; IQR, 5.08, 8.76 ng/L, p =0.044). D-dimer appeared to be associated with 
a history of stroke (3003.1 ng/mL [FEU]; IQR, 1513, 3067 ng/mL [FEU] vs. 1399.5 ng/mL 
[FEU]; 648.8, 2217 ng/mL [FEU], p = 0.062), although the difference was not statistically 
significant. When those patients with a measurable tricuspid regurgitant jet velocity were 
evaluated (N = 43), there was no significant correlation between D-dimer and tricuspid 
regurgitant jet velocity (r =0.25, p = 0.10). However, when the analyses were limited to 
patients with SS/SD/Sβ0 thalassemia, we observed associations between D-dimer and a 
history of thrombotic stroke (3035.2 ng/mL [FEU]; IQR 2559, 3494 vs. 1269.6 ng/mL 
[FEU]; IQR 688.4, 2347, p = 0.049), TAT and history of retinopathy (7.145 ng/L; IQR 
5.225, 12.01vs. 4.465 ng/L; IQR 3.215, 7.332, p= 0.018). There appeared to be a correlation 
between tricuspid regurgitant jet velocity and D-dimer (r = 0.3, p =0.067), although this was 
not statistically significant. Although no significant correlation was observed between 
plasma markers of thrombin generation and echocardiography-derived TRV, TRV may not 
be particularly sensitive for the diagnosis of PHT {Parent, 2011}. As right heart 
catheterizations were not obtained in all of the study subjects it is uncertain how many 
patients truly have PHT. However, as NT-proBNP is a surrogate for PHT {Machado, 
JAMA; Ataga, 2006}, the correlation between NT-proBNP and both D-dimer and TAT (see 
#3 above) suggests a likely association between these markers of thrombin generation and 
RHC-diagnosed PHT.  
Correlation of inflammatory cytokines with echocardiography-defined pulmonary 
hypertension. 
Levels of selected inflammatory cytokines were measured in 56 HbSS patients to evaluate 
their association with echocardiography-defined PHT {Ataga, 2008}. Patients with 
echocardiography-defined PHT had consistently higher median levels of IL-6 (4.7 ng/mL 
vs. 2.9 ng/mL; p = 0.06), interleukin-8 (5.4 ng/mL vs. 2.7 ng/mL; p = 0.07) and interleukin-
10 (0.57 ng/mL vs. 0.35 ng/mL; p = 0.10) compared with HbSS patients without PHT, 
although the differences were only of borderline statistical significance (Table 1). 
 
2
3

 
Rivaroxaban in Sickle Cell Disease 
 
 
Table 1 
Analyte 
PHT (N=19)  
Median 
(25th, 75th) 
No PHT (N=34) 
Median (25th, 
75th) 
p value 
Interleukin-6 
(pg/mL) 
4.7 (2.7, 7.8) 
2.9 (1.5, 6.5) 
0.06 
Interleukin-8 
(pg/mL) 
5.4 (2.4, 
15.5) 
2.7 (0, 7.9) 
0.07 
Interleukin-10 
(pg/mL) 
0.57 (0.25, 
1.2) 
0.35 (0.03, 
0.82) 
0.10 
Interferon-γ 
(pg/mL) 
31.3 (0, 85.7) 
13.3 (0, 71.4) 
0.76 
Tumor necrosis 
factor-α 
1.9 (0.7.8) 
3.3 (0.98, 21.9) 
0.25 
 
Laser Doppler velocimetry in SCD. 
We conducted a proof-of-principle study to determine whether pentosan polysulfate sodium 
(PPS) improves baseline blood flow in the microvasculature of patients with SCD {Kutlar, 
2012}. PPS has structural and functional similarities to, but considerably less anticoagulant 
activity than heparin, as well as potent blocking activity against cell adhesion to P-selectin. At 
the time that this double-blind, placebo-controlled, randomized,  multi-center study was 
discontinued, 19 of 41 enrolled patients had been randomized to the active PPS arm, 14 had 
received PPS, nine had received PPS for at least eight weeks, and two of the nine disclosed they 
had not taken their study drug reliably. In the seven evaluable patients, PPS was safe and non-
toxic when given for 8 to 12 weeks, and there was a highly significant reduction in plasma 
soluble VCAM-1 from pretreatment levels (p ≤ 0.015 at 2 wk; p < 0.001 at 8 wk). There also was 
a non-significant trend toward improved blood flow measured by laser Doppler velocimetry 
(LDV) in these same seven patients, but no evidence of improved soluble VCAM-1 levels or 
blood flow in the placebo group. This study demonstrates our experience with the conduct of 
studies evaluating microvascular blood flow with laser Doppler velocimetry. Dr. Neil Matsui 
will serve as a consultant in this application and will be responsible for interpreting the LDV test 
results. 
Anticoagulation with warfarin is safe in SCD. 
In a pilot study, we showed that low-intensity anticoagulation with warfarin (INR of 1.5 – 2.0) 
for 12 months appears safe in appropriately selected patients (unpublished data).  There were no 
bleeding episodes during the course of the study. In addition, the median baseline INR in the 4 
patients in the placebo arm was 1.1 (range: 1.0 to 1.1) and following treatment was 1.1 (range: 
1.0 to 1.2). The median baseline INR for the 3 patients in the low-intensity anticoagulation arm 
was 1.1 (range: 1.0 to 1.1) and following treatment was 1.7 (range: 1.4 to 1.9). Following 
treatment, patients on low-intensity anticoagulation had greater reductions in TAT (Mbaseline= 4 
µg/L, M12mth= 2 µg/L) and D-dimers levels (Mbaseline= 971 ng/mL, M12mth= 513 ng/mL) compared 
to patients on placebo who experienced relatively no change in their levels (TAT Mbaseline= 5.5 
µg/L and M12mth= 5.0 µg/L; D-dimers Mbaseline= 1050 ng/mL, M12mth= 871 ng/mL).  Finally, 

 
Rivaroxaban in Sickle Cell Disease 
 
despite concerns of the risk of bleeding in SCD patients, our clinical experience suggests that 
appropriately selected patients with SCD on standard intensity anticoagulation do not appear to 
have an increased risk of bleeding.   
 
RESEARCH DESIGN AND METHODS 
We will conduct a randomized, double-blind, placebo-controlled, crossover study to evaluate the 
efficacy and safety of rivaroxaban in SCD. We have selected this agent based on our preliminary 
data in sickle mice showing that ‘upstream’ TF inhibition achieves the desired effects on 
inflammation and endothelial activation, but that ‘downstream’ thrombin inhibition does not. 
The study will consist of three phases: 1) Screening/Baseline; 2) Treatment; and 3) Follow-up. 
The Screening/Baseline Phase will occur within 28 days of study drug administration and will 
include: informed consent, a history and physical examination, and clinical laboratory tests 
including: a complete blood count, routine coagulation studies, routine chemistries, chest x-ray, 
and serum or urine pregnancy test (if female, and of child-bearing capacity). The sequence of 
drug administration will be generated via block permuted randomization procedure. The 4-week 
Treatment Phase will consist of drug administration, efficacy assessments and safety assessments 
(including pregnancy testing in females of child-bearing capacity). After the first treatment 
period, there will be a washout period of 14 ± 3 days. In the second treatment phase, patients will 
be crossed over to receive rivaroxaban or placebo, depending on their initial treatment 
assignment. The total duration of the Treatment phase (including washout) will be 10 weeks. 
During the Follow-up Phase at week 12, patients will obtain their final study evaluation. Table 2 
provides a detailed schedule of assessments for the study period.  
Treatment: Subjects will receive rivaroxaban 20 mg/day (the approved dose to prevent stroke 
and systemic embolism in patients with non-valvular atrial fibrilation) and placebo for 4 weeks 
each, separated by a 2-week washout phase. Pill counting will be used to assess compliance. 
PT/INR will be monitored by an unblinded investigator to assess compliance with no other 
involvement in the study). If major bleeding or other serious adverse event occurs (see Appendix 
2), the study drug will be discontinued and the patient followed until resolution of the problem. 
Subjects that discontinue the study early will not be replaced. 
Eligibility Criteria:  
Inclusion Criteria:  
a) 18 to 65 years of age;  
b) HbSS or HbSβ0 thalassemia; serum creatinine ≤ 1.0 mg/dL men) or 1.2 mg/dl (women);  
c) ALT < 2 times upper limits of normal;  
d) platelet count ≥ 150,000 cu/mm;  
e) normal baseline PT/INR and aPTT;  
f) be in the non-crisis, “steady state” at enrollment with no severe pain episodes during the 
preceding 4 weeks;  
g) ability to understand the requirements of the study and be willing to give informed 
consent;  
h) women of childbearing age must be practicing an adequate method of contraception; 
i) if on hydroxyurea, must be on a stable dose for at least 3 months. The dose of 
hydroxyurea will not be adjusted during the study duration except for safety reasons.  

 
Rivaroxaban in Sickle Cell Disease 
 
Exclusion Criteria:  
a) hypersensitivity to any component of rivaroxaban;  
b) history of major GI bleeding or bleeding diathesis;  
c) baseline Hb < 5.5 g/dL; 
d) history of clinically overt stroke;  
e) brain MRI/MRA scan with evidence of Moya Moya;  
f) pregnant or breastfeeding;  
g) active liver disease or ALT > 3 times upper limit of normal;  
h) on chronic anticoagulant, NSAID or statin therapy;  
i) history of metastatic cancer;  
j) current alcohol abuse;  
k) on a chronic transfusion program or any blood transfusion in the prior 3 months; 
l) ingested any investigational drugs within the past 4 weeks 
m) use of CYP3A4/P-glycoprotein inducers such as carbamazepine, phenytoin, rifampin, and 
St John's wort; 
n) use of CYP3A4/P- glycoprotein inhibitors such as ketoconazole, indinavir/ritonavir, 
itraconazole, lopinavir/ritonavir, ritonavir, and conivaptan 
Assessments:  Activation of coagulation.: Plasma levels of TAT and D-dimer measured using a 
commercially available ELISA kit at baseline, and at 2 and 4 weeks following initiation of study 
drug 
Endothelial cell activation: Plasma levels of soluble VCAM-1 and soluble ICAM-1 measured 
using a commercially available ELISA kit at baseline, and at 2 and 4 weeks following initiation 
of study drug 
Inflammatory markers: Plasma levels of IL-6 (commercially available ELISA), high sensitivity 
CRP, MPO, IL-2, IL-8, TNFα, sPLA2 (multiple cytokine assay using Luminex MAP technology; 
UNC core facility) at baseline, and at 2 and 4 weeks following initiation of study drug  
Microvascular blood flow: We will analyze microvascular blood flow using laser Doppler 
velocimetry (LDV) (Perimed, PF5001, Stockholm, Sweden) assessments of post-occlusive 
reactive hyperemia (PORH). Measurements will be obtained at baseline and at 4 weeks 
following initiation of therapy. 
Safety Assessment: We will evaluate patients for major bleeding complications (any bleeding 
episode into critical sites, e.g. intracranial bleed, decrease in hemoglobin concentration of at least 
2g/dL from baseline or any prolonged bleeding that requires a blood transfusion) and other 
clinically relevant non-major or trivial   bleeding. We will also evaluate for episodes of SCD-
related events during scheduled follow-up visits, by employing a systems review, physical 
examination, vital signs, and routine laboratory tests. 
Termination Criteria:  Treatment with study drug will be discontinued at any time if the 
patient: a) withdraws consent; b) develops a major bleeding episode (defined as any bleeding 
episode into critical sites, e.g. intracranial bleed, decrease in hemoglobin concentration of at least 
2g/dL from baseline or any prolonged bleeding that requires a blood transfusion); or if, c) in the 
judgment of the investigator, continuation of the study drug will be hazardous to the patient. The 
UNC DSMB will review the protocol following the occurrence of the 1st treatment-related 
serious adverse event. The study will be terminated at the occurrence of treatment-related serious 
adverse events, including major bleeding, in up to 3 study participants. 

 
Rivaroxaban in Sickle Cell Disease 
 
 
 
STATISTICAL METHODS 
Normally distributed variables will be presented with means and SD, while summary of variables 
not normally distributed will be presented with medians and ranges or geometric means and SD 
as appropriate. The main study objective is to examine the difference between the measurements 
at baseline and following 4 weeks of treatment. We will evaluate the effect of rivaroxaban on the 
outcome measures by performing a comparison of treatment by visit using paired t-tests 
subsequently followed by crossover ANOVA model testing to assess the carry-over effect and 
treatment effect. In addition, when outcome measures are not normally distributed, we will 
perform appropriate nonparametric tests. The effect of rivaroxaban on various plasma markers 
and microvascular blood flow will be estimated using a multiple linear regression model. While 
the study is adequately powered to evaluate the effect of rivaroxaban on soluble VCAM-1 and 
IL-6, analysis of the effect of rivaroxaban on the other indicated endpoints are exploratory. 
Sample Size Justification:  The primary outcome measures are sVCAM-1 and IL-6. Based on 
our preliminary data in SCD patients, log (sVCAM) and log(IL-6) are normally distributed with 
SD of 0.49 and 0.95, respectively. In a 2x2 crossover design, assuming a correlation of 0.65 for 
the pre- and post-treatment measures, to detect a difference of 0.245 in the change of 
log(sVCAM) and 0.475 in the change of log(IL-6) between the rivaroxaban and placebo groups 
requires a minimum sample size of 15 per sequence (a total sample size of 30) at 80% power and 
α =0.05. Assuming a 10% dropout rate, a total of 34 patients is required for this study (17 in each 
sequence). 
Data Management: A standardized set of data collection forms will be designed using the RED 
Cap system and a secure database will be created. All data will be stored under password 
protection on a secured server. A data manager will handle all data entry and database security. 
This individual will work closely with the statistician on database design and quality assurance 
procedures. 
Timeline: We anticipate beginning recruitment in year 2, following studies on rivaroxaban in 
sickle mice. Recruitment for this clinical study is expected to take up to 36 months. The 
remaining few months will be dedicated to completing the studies, data analysis and publication. 
 
HUMAN SUBJECTS 
Protection of Human Subjects 
1. Human Subjects Involvement and Characteristics: This study seeks to evaluate the 
efficacy and safety of the factor Xa inhibitor, rivaroxaban, in SCD. Thirty two patients with SCD 
(HbSS or Sβ0 thalassemia) that meet the eligibility criteria will be enrolled in a randomized, 
double-blind, placebo-controlled, crossover trial. At the time of enrollment, all study subjects 
will be in the non-crisis, steady state. Informed consent will be obtained according to IRB 
approved procedure. Patients will be closely monitored for adverse events following 
randomization to the study drug. The primary goal of this study is to evaluate the effect of 
rivaroxaban on plasma levels of soluble VCAM and IL-6. Furthermore, we will evaluate plasma 
other markers of endothelial activation (soluble ICAM) and other inflammatory markers (high 
sensitivity CRP, MPO, IL-2, IL-8, TNFα, sPLA2), coagulation activation (TAT and D-dimer), 

 
Rivaroxaban in Sickle Cell Disease 
 
assessment of microvascular blood flow using laser Doppler velocimetry and safety as described 
in the application.  
2. Sources of Research Material: Enrollment and study participation will involve the collection 
of a full range of clinical data, including medical history. We will obtain clinical and laboratory 
data as well as assessments of microvascular blood flow at specified intervals during the course 
of the studies as described in the research plan.  
3. Plans for Recruitment: Patients will be recruited from amongst the patients that routinely 
receive their care at the UNC Comprehensive Sickle Cell Program. Dr Ataga and/or one of the 
co-investigators will discuss the studies with all eligible patients. Interested patients will be 
provided with a copy of the consent form(s), and the study coordinator or PI (or a co-
investigator) will carefully go over the consent with each candidate before he/ she signs. We will 
strive to ensure that all patients understand the nature of the study and all their questions will be 
answered.  The original consent form will be placed in the study files, in a secure, locked 
cabinet.  Potential subjects will be contacted during regularly scheduled clinic visits, but may be 
contacted at home by study personnel if they are known to meet the eligibility criteria. The PI 
and study nurse involved in the study are regular staff of the program. Samples obtained from 
patients specifically for these studies will be collected as approved by the IRB. This is 
anticipated to occur during specified study visits.   
4.  Potential Risks: The study entails physical risk associated with venipuncture to obtain blood 
samples; administration of rivaroxaban; and pneumatic occlusion cuff placed around the arm to a 
suprasystolic pressure (~ 200 mmHg) during the assessment of microvascular blood flow. The 
most significant risks of blood tests are discomfort and bruising.  There is still limited clinical 
experience with the use of rivaroxaban in the general population, and even less so in SCD. 
However, published studies indicate that the most common complications of rivaroxaban are 
bleeding, bruising, peripheral edema, dizziness, headache, pyrexia, fatigue, syncope, pruritus, 
rash, blister, diarrhea, thrombocytopenia, extremity pain, and back pain. Pneumatic occlusion of 
the arm to a suprasystolic pressure is uncomfortable. However, this technique has been safely 
performed in SCD patients. Patients will be monitored very closely for any laboratory or clinical 
complications during the course of the studies.  
5. Procedures for Minimizing Risks: We will do everything possible to minimize the risks 
associated with participating in the studies. We will ensure there are no contraindications to 
receiving rivaroxaban. This study will be monitored by a DSMB, which will review all reports to 
determine if there is a safety concern. Finally, we have established data safety and monitoring 
procedures as described below.  
Risks to Privacy:  All clinical information, including personal identifiers obtained on research 
subjects will be maintained in a locked and secured file drawer with access limited to clinical 
staff. All data will be coded to protect patient confidentiality. We will make all effort to maintain 
patient confidentiality. 
6. Potential Benefits of the Proposed Research to the Subjects and others: The available 
treatments in SCD remain limited.  This study will help to define the contribution of coagulation 
activation to the pathophysiology of SCD.   
7. Importance of the Knowledge to be Gained: Despite our improving understanding of the 
pathophysiology of SCD, treatment options for several SCD-related complications remain quite 
limited. This proposal aims to increase our understanding of the contribution of coagulation 

 
Rivaroxaban in Sickle Cell Disease 
 
activation to the pathophysiology of SCD. The risks to patients from participating in this study 
are modest and are reasonable in relation to the potential benefits and the importance of 
knowledge to be gained. 
8.  Data and Safety Monitoring Plan: All SAEs will be reported to the IRB and the DSMB. In 
addition, after 5 patients and subsequently every 6 months, all of the available safety data will be 
presented by treatment group to the DSMB in a confidential report. The DSMB will review and 
determine if there is a safety concern. The DSMB will review the study after the occurrence of 
the first treatment-associated SAE. The study will be terminated at the occurrence of 3 treatment-
related serious adverse events, including bleeding complications. The statistician who conducts 
the randomization and generates the tables for the DSMB will be an ‘independent statistician’ 
not otherwise involved in the study and will not be responsible for the data analysis at the 
completion of the study. 
The UNC TraCS DSMB is a committee that has been established within the UNC School of 
Medicine. The membership is appointed by the Dean (or his designee), and is available to review 
any clinical trial that is being carried out by a UNC investigator. Most multi-center clinical trials 
funded by the NIH or by industry have national data and safety monitoring boards organized by 
the sponsoring organization. However, single- or dual-site clinical trials such as the study 
proposed in this application depend on a local DSMB such as the one based here at UNC. The 
current makeup includes a chair (Dr. Ross Simpson), an ethicist, an 
epidemiologist/biostatistician, and several clinical researchers. In addition, ad hoc members are 
added to the DSMB when need for scientific expertise arises.  
9. Inclusion of Women and Minorities: Based on the results of our studies in this patient 
population to date, we anticipate that enrolled subjects will include 50-55% women. We have 
achieved this in the past without special efforts to recruit women, and this reflects the gender 
distribution of our patient population. In addition, due to the nature of the disease to be studied 
(sickle cell disease), over 95% of patients will identify themselves as African-American. A small 
number identifying themselves as Hispanic or Native American may be available; such patients 
typically comprise less than 2% of our clinic patients with this disease.  
10. Inclusion of Children: As rivaroxaban is not yet approved in children, no patients less than 
18 years will be evaluated in this study.  

 
Rivaroxaban in Sickle Cell Disease 
 
1 Screening assessments and baseline assessments for Treatment Phase 1 may be combined if eligibility can be established before treatment is initiated 
2 CBC with differential and reticulocyte count   3 BUN, creatinine, albumin, total and direct bilirubin, ALT, AST, LD, AlkPhos, GGT   4 PT/INR and aPTT 
 
Screening1   
Treatment 1 
2 Week 
Washout 
Treatment 2 
F/U 
Assessment/Event 
Day -28 – -1 
BL1 
Wk 2 
Wk 4 
 
BL 
Wk 2 
Wk 4 
Wk 6 
Informed consent 
X 
 
 
 
 
 
 
 
 
Medical history 
X 
 
 
 
 
 
 
 
 
Vital Signs 
X 
X 
X 
X 
 
X 
X 
X 
X 
Physical exam 
X 
X 
 
 
 
X 
 
 
X 
MRI/MRA 
X 
 
 
 
 
 
 
 
 
Hematology2 
X 
X 
 
 
 
X 
 
 
X 
Chemistries3 
X 
X 
 
 
 
X 
 
 
X 
Coags4 
X 
X 
 
 
 
X 
 
 
X 
Chest X-ray 
X 
 
 
 
 
 
 
 
 
Serum/urine pregnancy test5 
 
X 
X 
X 
 
X 
X 
X 
 
Biomarkers 
 
X 
X 
X 
 
X 
X 
X 
 
Laser doppler velocitometry 
 
X 
 
X 
 
X 
 
X 
 
Randomization 
 
X 
 
 
 
 
 
 
 
Study drug initiation 
 
X 
 
 
 
X 
 
 
 
Adverse event probe 
 
X 
X 
X 
 
X 
X 
X 
X 
Record concomitant medications 
X 
X 
 
 
 
X 
 
 
X