Standard-dose Apixaban AFtEr Very Low-dose ThromboLYSis for Acute Intermediate-high Risk Acute Pulmonary Embolism

The purpose of this study is to examine the degree to which pulmonary embolism (clot) can be dissolved when treated with a very low dose of a systemic thrombolytic drug (clot buster) along with standard anticoagulant therapy as compared to the standard of care anticoagulant therapy alone.

The OVERALL OBJECTIVE of this investigation is to determine whether very low-dose intravenous tissue-type plasminogen activator \[tPA\] (24 mg) + standard anticoagulation therapy (intravenous heparin) for treatment of acute PE (pulmonary embolism) in intermediate-high risk patients will have superior clot lysis (breakdown of clot) by chest CTA (computed tomography angiography) at 24 ± 6 hours post infusion compared to standard of care treatment alone. Acute intermediate-high risk PE patients are those with acute symptoms \<14 days), simplified Pulmonary Embolism Severity Index (sPESI)\>0, normal systemic arterial blood pressure (\>90mmHg) without vasopressor support, elevated biomarkers (troponin or BNP), and evidence of RV dysfunction (right ventricular to left ventricular ratio\>0.9).The study is planned to evaluate the reduction in clot burden based on the obstruction index using the Refined Modified Miller Score (RMMS), improvement in right ventricular (RV) function, and overall safety in the two treatment groups. 40 Subjects with intermediate-high risk PE (hemodynamically stable PE with a RV/LV ratio ≥ 0.9, elevated biomarkers, and sPESI\>0) will be recruited and randomized to one of two treatment groups: 24mg of systemic (IV) tPA + IV unfractionated heparin versus saline placebo + IV unfractionated heparin. After delivery of the systemic (IV) tPA/placebo, patients will continue IV unfractionated heparin therapy for at least 24 hours. If there is no evidence of active bleeding nor significant hemoglobin drop (i.e., ≥ 2 mg/dL), patients will be transitioned to standard dose apixaban, 10 mg twice-daily x one week followed by 5 mg twice-daily for at least 6 months. Some patients will require indefinite apixaban therapy based on patient-specific factors, including unprovoked nature of PE event, and/or persisting DVT/PE risk factors. Finally, consideration will be given for decreasing the apixaban dose to 2.5 mg twice-daily after 6 months. Apixaban was selected as the anticoagulant of choice due to its very favorable bleeding profile in large clinical trials, which is an important consideration when prescribing an anticoagulant following systemic thrombolysis. Within 24 ± 6 hours post study drug infusion, a repeat chest CTA and echocardiogram will be performed. sPESI will also be calculated at this timepoint.At Day 30, 180 and 365, all subjects will have clinic visits which will include a physical exam, repeat echocardiogram if previous echo was abnormal, 6 minute walk test (6MWT), quality of life questionnaires, assessment of adverse and bleeding events and a review of concomitant medications including compliance with apixaban. At Days 3, 7, 90 and 270, a remote health check will occur via telephone or email assessing adverse and bleeding events, alongside a review of concomitant medications (including an assessment of compliance with apixaban).The standard of care for patients with submassive PE is to either receive anticoagulant therapy, EKOS (Catheter Assisted Thrombolysis) or thromboectomy. tPA is given at the FDA approved dose (100mg) occasionally at doses much higher than our study proposes. PatientS with PE will have the initial CTA, echocardiogram and lab work as standard of care. The follow up CTA is usually standard of care at Day 30 and the follow up echocardiograms are considered standard of care if the previous echocardiogram was abnormal.The study is being done as a proof of concept that low dose tPA is effective in clot lysis and will result in far less risk than the FDA dose. If our study achieves its aims, the research will advance clinical practices in treating pulmonary embolism by reporting the safety of lower dose tPA and opening opportunities to further explore the use of lower dose tPA to improve patient safety and outcomes.

Eligibility Criteria:
Inclusion Criteria:

* Chest CT angiogram (CTA) evidence of proximal Pulmonary Embolism (PE) with a filling defect in at least one main pulmonary artery or lobar artery
* PE symptom duration ≤14 days
* Intermediate-high risk PE: defined as RV dysfunction with an RV/LV diameter ≥ 0.9, sPESI \> 0, and either troponin \> 0.05ng/mL or BNP \> 100 pg/mL, and hemodynamically stable (systolic blood pressure \> 90mmHg without the use of vasopressor support)
* Randomization within 24 + 4 hours of anticoagulation
* Signed and dated informed consent obtained from subject or legally authorized representative before initiation of any study procedures

Exclusion Criteria:

* Weight \> 130kg or \< 40 kg on day of randomization
* Stroke or transient ischemic attack (TIA), head trauma, or other active intracranial or intraspinal disease within one year
* Recent (within one month) or active bleeding from a major organ
* Major surgery within 14 days
* Clinician deems the subject too high-risk for bleeding using HAS-BLED criteria
* History of any hematologic disease or coagulopathy
* Cirrhosis (as determined by Child-Pugh B or C)
* History of heparin-induced thrombocytopenia (HIT)
* Hemodynamic instability defined as systolic blood pressure (SBP) less than 90mmHg and/or use of vasopressors for greater than 15 minutes
* Severe hypertension as defined as SBP greater than 180mmHg
* Cardiac arrest or active cardiopulmonary resuscitation (CPR)
* Receiving neuraxial anesthesia or undergoing spinal puncture
* Patient with prosthetic heart valves
* Evidence of irreversible neurological compromise
* Evidence of poor functional status
* History of major gastrointestinal bleed within the last month
* Active gastric or duodenal ulcers
* Use of thrombolytics or glycoprotein IIb/IIIa antagonists within 3 days prior to diagnosis
* Lovenox administration within 12 hours of randomization
* Direct-acting oral anticoagulant use (dabigatran, rivaroxaban, apixaban, or edoxaban) with last known dose within 48 hours
* Hemoglobin \< 10 g/dL
* Creatinine clearances \< 60 mL/min
* Platelets \< 100 thousand/µL
* INR \> 1.4
* Alanine transaminase (ALT) or aspartate transaminase (AST) ≥ 2 times upper limit of normal (ULN)
* Total bilirubin (TBL) ≥ 1.5 times ULN (except due to confirmed Gilbert's syndrome)
* Patient is pregnant (positive pregnancy test; women of childbearing capacity must be tested prior to enrollment) or breast feeding
* Patient who is a prisoner, or if subject who becomes compulsory detained
* Active cancer defined as diagnosis of cancer within six months before the study inclusion, or receiving treatment for cancer at the time of inclusion or any treatment for cancer during 6 months prior to randomization, or recurrent locally advanced or metastatic cancer
* Known allergy, hypersensitivity or thrombocytopenia from heparin, tPA, or apixaban or iodinated contrast except for mild-moderate contrast allergies for which steroid pre-medication can be administered within 12 hours prior to the CTA
* HIV/AIDS