Patient Inclusion Criteria

At least 18 years of age at the time of signing the ICF. Hospitalized for COVID-19. Diagnosed with COVID-19 as defined by having at least 2 of the following signs or symptoms within the past 2 days: - Fever defined as a body temperature of ≥ 38.0 °C oral, or ≥ 38.3 °C rectal, ≥37.7 °C forehead or ≥38.7°C aural (axillary temperatures are not allowable); - Cough; - Fatigue; - Shortness of breath. Radiographic evidence (chest x-ray or CT scan) of one the following: - Ground-glass opacities, or - Local or bilateral patchy infiltrates, or - Interstitial pulmonary infiltrates. Oxygen requirements: - SpO2 ≤ 94% on ambient air OR - Requires supplemental oxygen administration by nasal cannula, simple face mask, or other similar oxygen delivery device. Male and/or female subjects. - Contraception use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. All subjects (male or female) who are of childbearing potential must agree to use highly effective contraception during the study. Female subjects and male partners of female subjects must continue to use highly effective contraception for 30 days after the last dose of study drug. Female subjects should not donate oocytes during this time. Male subjects and female partners of male subjects must continue to use highly effective contraception for 90 days. Male subjects must agree not to donate sperm during this time. Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception for the subject. Note: Ethinyl estradiol is the primary estrogen used in hormonal contraceptives. The progestin component consists of norethindrone, levonorgestrel, norgestrel, norethindrone acetate, ethynodiol diacetate, norgestimate, desogestrel, and drospirenone. As BLD-2660 is a weak CYP3A4 inducer, exposure to both the estrogen and progestin components in hormonal contraceptives may be decreased, resulting in an increased risk of pregnancy. As such, it is recommended that subjects who are on hormonal contraceptives for birth control should use an alternate means of contraception (condoms, diaphragms, intrauterine device (IUD), other barrier methods, sexual abstinence, etc.) during participation in the study. Women of childbearing potential must have a negative serum pregnancy test at Screening within 72 hours prior to first administration of study drug. Women not of childbearing potential must be postmenopausal (defined as cessation of regular menstrual periods for at least 1 year Capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the ICF and in this protocol

Patient Exclusion Criteria

Active bacterial pneumonia infection Known active tuberculosis (TB). History of Child-Pugh B or C cirrhosis. History of ischemic heart disease or myocardial infarction or acute coronary syndrome. Subjects requiring supplemental oxygen ≥0.75 FiO2. It is not in the best interest of the subjects to participate, in the opinion of the treating Investigator. Female subjects who are pregnant or breastfeeding or expecting to conceive within the projected duration of the study, starting with the screening visit through 90 days after the last dose of study drug. The following laboratory parameters are excluded: - Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >5 x upper limit of normal (ULN); - Creatinine clearance < 50 mL/min. Requiring, or expected to require mechanical ventilation at screening. Treatment with chloroquine or hydroxychloroquine at study entry. Treatment with anti-IL 6, anti-IL-6 receptor antagonists, or with Janus kinase inhibitors (JAKi) in the past 30 days or plans to receive during the study period. Participation in any other clinical study of an experimental drug treatment for COVID-19 within 6 half-lives of the experimental treatment. Note: Subjects participating in an observational study are an exception to this criterion and may qualify for the study with Sponsor approval. Note: Subjects who have entered the follow-up phase of an investigational study may participate as long as it has been 4 weeks after the last dose of the previous investigational agent. - Unable to swallow solid oral medication or known malabsorption disorder. - Subjects who have allergy to BLD-2660 or inactive components of BLD-2660.