Baloxavir and Oseltamivir for the Treatment of Severe Influenza Infection in Immunocompromised Patients

PRIMARY OBJECTIVE: I. To compare the efficacy of baloxavir marboxil (baloxavir) in combination with oseltamivir to oseltamivir monotherapy as measured by changes in influenza viral loads at day 1 from baseline for treatment of severe influenza infections in immunocompromised hosts (such as hematopoietic cell transplant \[HCT\] recipients and hematological malignancy \[HM\] patients) and compare the main clinical outcome, complicated hospital stay between the intervention arm and control arm. SECONDARY OBJECTIVES: I. To compare the efficacy of baloxavir in combination with oseltamivir to oseltamivir monotherapy as measured by changes in influenza viral loads at day 3, 7, 14 and 30 from baseline. II. To measure the incidence of baloxavir and oseltamivir resistance, development of lower respiratory tract infections (LRTI), oxygen requirement, respiratory failure, changes in microbiome of the upper airway, length of hospital stay and all-cause mortality at day 30 while on baloxavir and/or oseltamivir in these immunocompromised hosts. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients receive oseltamivir orally (PO) twice daily (BID) for up to 10 days and baloxavir marboxil PO every 72 hours for a total of 3 doses in the absence of disease progression or unacceptable toxicity. ARM II: Patients receive oseltamivir PO BID for up to 10 days in the absence of disease progression or unacceptable toxicity. After completion of study, patients are followed up at 30 days.