Moxetumomab Pasudotox-tdfk (Lumoxiti(TM)) and Either Rituximab (Rituxan(R)) or Ruxience for Relapsed Hairy Cell Leukemia

Moxetumomab pasudotox-tdfk is administered at 30-40 ug/Kg intravenous (iv) over 30 min given on days 1, 3, 5 of each cycle.

Rituximab will be administered at 375mg/m\^2 intravenous (iv), 50-400 mg/hour (hr). On cycle 1, Rituximab is given on day -2, on subsequent cycles, Rituximab is given on day 1.

Ruxience will be administered at 375mg/m\^2 intravenous (iv), 50-400 mg/hour (hr). On cycle 1, Ruxience is given on day -2, on subsequent cycles, Ruxience is given on day 1 (Delta)

12 mg Cycle 1, Day -2; Cycles 2-8, Day 1. Administer 0.5-2 hours before rituximab/Ruxience. If participant has previous reaction to rituximab/Ruxience, give 12mg. If participants tolerate rituximab/Ruxience without problems, may hold at discretion of provider. Pre-medications are given prior to rituximab/Ruxience on day 1.

650 mg Cycle 1, Day -2, Day 1, Day 3, Day 5. To be given 30-90 minutes prior to every moxetumomab pasudotox-tdfk infusion and recommended every 6 hours x 4 after the end of infusion; Cycles 2-8, Day 1, Day 3, Day 5. To be given 30-90 minutes prior to every moxetumomab pasudotox-tdfk infusion and recommended every 6 hours x 4 after the end of infusion. Pre-medications are given prior to rituximab/Ruxience on day 1.

25-50 mg Cycle 1, Day -2; Cycles 2-8, Day 1. Pre-medications are given prior to rituximab/Ruxience on day 1. May be given prior to moxetumomab pasudotox-tdfk at discretion of principal investigator.

20-40 mg Cycle 1, Day -2; Day 1, Day 3, Day 5. To be given 30-90 minutes prior to every moxetumomab pasudotox-tdfk infusion and is recommended every 12 hours x 2 after the end of infusion; Cycles 2-8, Day 1, Day 3, Day 5. To be given 30-90 minutes prior to every moxetumomab pasudotox-tdfk infusion and is recommended every 12 hours x 2 after the end of infusion. Pre-medications are given prior to rituximab/Ruxience on day 1.

81 mg Cycle 1, Days 1-8; Cycles 2-8, Days 1-8. Only if platelet counts ≥ 100 x 109/L.