ARM 3 1. Unable to take oral medication 2. Any known allergic reactions to selinexor or concomitant medication-related contra-indications to selinexor. 3. Severe critical COVID-19 infection defined as: a) Requiring invasive or non-invasive mechanical ventilation, ECMO b) Anticipated unlikely to survive within 48 hours 4. In the opinion of the investigator and primary oncologist, participation in the study would not be in the best interests of the participant 5. Severe renal impairment defined as creatinine clearance (CrCL) < 20ml/min as calculated using the Cockcroft Gault formula 6. Severe hepatic impairment defined as aspartate transaminase (AST) or alanine transaminase (ALT) > 5 x upper limit of normal (ULN)

ARM 3 1. Unable to take oral medication 2. Any known allergic reactions to selinexor or concomitant medication-related contra-indications to selinexor. 3. Severe critical COVID-19 infection defined as: a) Requiring invasive or non-invasive mechanical ventilation, ECMO b) Anticipated unlikely to survive within 48 hours 4. In the opinion of the investigator and primary oncologist, participation in the study would not be in the best interests of the participant 5. Severe renal impairment defined as creatinine clearance (CrCL) < 20ml/min as calculated using the Cockcroft Gault formula 6. Severe hepatic impairment defined as aspartate transaminase (AST) or alanine transaminase (ALT) > 5 x upper limit of normal (ULN)