GRAVITAS-301: A Study of Itacitinib or Placebo in Combination With Corticosteroids for Treatment of Acute Graft-Versus-Host Disease

Inclusion Criteria:

- Has undergone 1 allo-HSCT from any donor (related or unrelated with any degree of HLA
matching) and any donor source (bone marrow, peripheral blood stem cells, or cord
blood) for a hematologic malignancy or disorder. Recipients of myeloablative and
reduced-intensity conditioning regimens are eligible.

- Clinically suspected Grade II to IV aGVHD as per MAGIC criteria, occurring after
allo-HSCT and any GVHD prophylaxis regimen.

- Evidence of myeloid engraftment. Use of growth factor supplementation is allowed.

- Serum creatinine ≤ 2.0 mg/dL or creatinine clearance ≥ 40 mL/min measured or
calculated by Cockroft Gault equation.

- Willing to avoid pregnancy or fathering children.

- Able to give written informed consent and comply with all study visits and procedures.

- Able to swallow and retain oral medication.

Exclusion Criteria:

- Has received more than 1 allo-HSCT.

- Has received more than 2 days of systemic corticosteroids for aGVHD.

- Presence of GVHD overlap syndrome.

- Presence of an active uncontrolled infection.

- Known human immunodeficiency virus infection.

- Active hepatitis B virus (HBV) or hepatitis C virus infection that requires treatment
or at risk for HBV reactivation.

- Participants with evidence of relapsed primary disease, or participants who have been
treated for relapse after the allo-HSCT was performed.

- Any corticosteroid therapy for indications other than GVHD at doses > 1 mg/kg per day
methylprednisolone (or prednisone equivalent) within 7 days of randomization.

- Severe organ dysfunction unrelated to underlying GVHD, including:

- Cholestatic disorders or unresolved veno-occlusive disease of the liver.

- Clinically significant or uncontrolled cardiac disease.

- Clinically significant respiratory disease that requires mechanical ventilation
support or 50% oxygen.

- Currently breast feeding.

- Received JAK inhibitor therapy after allo-HSCT for any indication. Treatment with a
JAK inhibitor before allo-HSCT is permitted.

- Treatment with any other investigational agent, device, or procedure within 21 days
(or 5 half-lives, whichever is greater) of enrollment.

- Any medical complications or conditions that would, in the investigator's judgment,
interfere with full participation in the study, including administration of study drug
and attending required study visits; pose a significant risk to the participant; or
interfere with interpretation of study data.

- Known allergies, hypersensitivity, or intolerance to any of the study medications,
excipients, or similar compounds.