Study of the Efficacy and Safety of STI-5656 (Abivertinib Maleate) in Subjects Hospitalized With COVID-19

Inclusion Criteria: * Confirmed infection with SARS-CoV-2 per World Health Organization (WHO) criteria (including positive RT-PCR nucleic acid test of any specimen \[eg, respiratory, blood, urine, stool, or other bodily fluid\]) within 7 days of randomization * Hospitalized with COVID-19 pneumonia (documented radiographically) and oxygen saturation \<94% on room air or subject requires supplemental oxygen * Able to swallow capsules * Willing to follow contraception guidelines * Subject or family member/caregiver must have provided written informed consent which includes signing the institutional review board approved consent form prior to participating in any study related activity. However, if obtaining written informed consent is not possible, other procedures as provided in the March 27th, 2020 FDA Guidance on Conduct of Clinical Trials of Medical Products during COVID-19 Pandemic, Question 10, may be used Exclusion Criteria: * Known cardio-pulmonary resuscitation within 14 days prior to randomization * Pregnant or breast feeding * Suspected uncontrolled active bacterial, fungal, viral, or other infection (besides infection with SARS-CoV-2) * Alanine aminotransferase (ALT) ≥ 3x upper limit of normal (ULN) and total bilirubin \> 2x ULN * QTcF prolongation \>480 milliseconds * Uncontrolled or untreated symptomatic arrhythmias, myocardial infarction within the last 6 weeks, or congestive heart failure (NYHA Grade 3 or 4). Exception: Subjects with controlled, asymptomatic atrial fibrillation during screening are allowed to enroll * Treatment with a strong cytochrome P450 (CYP3A4 inhibitor (within 14 days before first dose of study drug) or inducer (within 7 days before first dose of study drug) * Received anti-rejection or immunomodulatory drugs (eg, anti-cytokines, BTK inhibitors, JAK inhibitors, PI3K inhibitors) within 30 days before randomization on study * Concurrent participation in another clinical trial involving therapeutic interventions (observational study participation is acceptable) * Any condition that confounds the ability to interpret data from the study * Relevant renal impairment (eGFR \<60 mL/min) * Any significant medical condition, laboratory abnormality or psychiatric illness that would interfere or prevent the subject from participating in the study