The investigators are evaluating the role of a low dose of tocilizumab in treating acute chest syndrome in patients with sickle cell disease. Tocilizumab inhibits interleukin-6 (IL-6) receptors and is used to treat rheumatoid arthritis and severe cytokine release syndrome, which can be seen with chimeric antigen receptor T-cell (CAR-T) therapy, and it is also authorized for treatment of COVID-19. Since IL-6 levels are elevated in the sputum of patients with acute chest syndrome, the investigators are hopeful that this will be an effective strategy. The investigators will be looking at how a low dose of tocilizumab affects oxygen status, clinical outcomes, and laboratory markers in patients admitted to the hospital with acute chest syndrome.

In this randomized, placebo-controlled, double-blinded phase II study, enrolled patients admitted to the University of Chicago who are diagnosed with acute chest syndrome will receive one dose of tocilizumab 80 mg IV and one normal saline placebo dose. The order of these doses will be randomized at a 1:1 ratio. After collecting oxygenation data as a baseline for 8 hours, patients will then receive tocilizumab versus placebo as their early dose and then the opposite (placebo versus tocilizumab) 48 hours later. Clinical, laboratory, and patient-reported outcome data will be collected during their admission and compared between arms.

Inclusion Criteria:

• Adults ≥ 12 years of age
• Prior diagnosis of sickle cell disease (Hb SS, Hb SC, Hb Sb+, and Hb Sb0)

Exclusion Criteria:

• Pregnant patients or breastfeeding mothers.
• Prior treatment with gene therapy or a stem cell transplant.
• Current enrollment in a clinical trial involving an FDA-regulated drug or biologic.
• Current neutropenia (absolute neutrophil count < 1000/mm^3)
• Current thrombocytopenia (platelet count < 50,000 mm^3)
• Aspartate aminotransferase (AST) or alanine transaminase (ALT) > 10 times the upper limit of normal (ULN)
• History of tuberculosis (TB).
• Positive purified protein derivative (PPD) TB screening test.
• On active therapy with a Bruton's tyrosine kinase-targeted agent, which include the following: Acalabrutinib, Ibrutinib, Zanubrutinib
• On active therapy with a JAK2-targeted agent, which include the following: Baricitinib, Ruxolitinib, Tofacitinib, Upadacitinib
• Any of the following biologic immunosuppressive agent (and any biosimilar versions thereof) administered in the past 6 months:

Abatacept, Adalimumab, Alemtuzumab, Atezolizumab, Belimumab, Blinatumomab, Brentuximab, Certolizumab, Daratumumab, Durvalumab, Eculizumab, Elotuzumab, Etanercept, Gemtuzumab, Golimumab, Ibritumomab, Infliximab, Inotuzumab, Ipilimumab, Ixekizumab, Moxetumomab, Nivolumab, Obinutuzumab, Ocrelizumab, Ofatumumab, Pembrolizumab, Polatuzumab, Rituximab, Sarilumab, Secukinumab, Tocilizumab, Tositumumab, Tremelimumab, Urelumab, Ustekinumab

The study statistician will generate randomizations using the method of permuted block randomization. The pharmacy will access the prepared randomization list via REDCap (a module separate from the clinical REDCap database) to guide tocilizumab versus placebo administration at the time of placing an inpatient order. Prior to randomization, the SpO2 to FiO2 ratio will be determined over an 8-hour period to serve as a baseline measure. Thus, randomization will be done at the time of placing the initial order for inpatient tocilizumab versus placebo, not at the time of enrollment. Patients, study investigators, and inpatient clinicians will all be blinded to the patient's randomized group assignment. Only the investigational pharmacy will be aware of the randomization arm.