- Following the completion of the phase II portion, enrolled patients will be randomized 1:1 to Arm C (isoquercetin) or Arm D (placebo). The dose for Arm C will be determined after evaluation of the Phase II portion of the trial. The protocol will be amended when the decision is made whether to proceed to Phase III and what dose to use for Arm C. The study will be double-blinded to treatment arm. Lower extremity ultrasound will be performed at 56 days. Baseline D-dimer and correlative labs will be drawn at Day 1 and at 56 days. Patients will be followed for survival after completion of 56 days.