Study of Duvelisib in Combination With Rituximab vs Rituximab in Subjects With Previously Treated Follicular Lymphoma

Inclusion Criteria: * Diagnosis of CD20-positive FL: * Histology grades 1, 2 or 3a * Biopsy-confirmed histopathological diagnosis of FL. Biopsy specimen should be obtained ≤2 years prior to randomization, unless medically contraindicated * CD20 immunophenotyping performed ≤2 years prior to randomization * First or subsequent relapse following at least one induction therapy regimen containing rituximab in combination with an anthracycline or rituximab in combination with an alkylating agent * Patients in first relapse must be chemoresistant or intolerant to chemotherapy * No response or disease progression ≤ 24 months from start of last previous therapy * At least 1 measurable disease lesion \>1.5 cm in at least one diameter by CT/CT-PET or magnetic resonance imaging (MRI) in an area of no prior radiation therapy, or in an area that was previously irradiated that has documented progression Exclusion Criteria: * Clinical evidence of other indolent forms of lymphoma (e.g., marginal zone lymphoma \[MZL\], small lymphocytic lymphoma \[SLL\]) * Transformation to a more aggressive subtype of lymphoma or grade 3b FL * Refractory to rituximab: defined as disease progression while receiving or within 6 months of completing either weekly rituximab induction therapy, or rituximab-based chemoimmunotherapy induction * Intolerance to rituximab or severe allergic or anaphylactic reaction to any humanized or murine monoclonal antibodies * Prior allogeneic hematopoietic stem cell transplant (HSCT) * Known Central Nervous System (CNS) lymphoma; subjects with symptoms of CNS disease must have a negative CT scan and negative diagnostic lumbar puncture * Prior treatment with a PI3K inhibitor or BTK inhibitor * History of tuberculosis within the preceding two years * Ongoing systemic bacterial, fungal, or viral infections at randomization (defined as requiring IV antimicrobial, antifungal or antiviral agents) * Subjects on antimicrobial, antifungal or antiviral prophylaxis are not specifically excluded if all other I/E criteria are met * Prior, current, or chronic hepatitis B or hepatitis C infection, positive result for hepatitis B surface antigen (HBsAg) or hepatitis B core antibody (HBcAb) or hepatitis C virus antibodies (HCV Ab) * History of stroke, unstable angina, myocardial infarction, or ventricular arrhythmia requiring medication or mechanical control within the last 6 months