Study Evaluating Safety and Efficacy of INCB050465 Combined With Bendamustine and Obinutuzumab in Relapsed or Refractory Follicular Lymphoma (CITADEL-102)

Inclusion Criteria: * Histologically confirmed FL. * Documented CD20+ FL. * Relapsed or refractory to any prior rituximab-containing regimen. * Previously treated with a maximum of 4 cancer-directed treatment regimens. * At least 1 measurable lesion \> 1.5 cm in at least 1 dimension by computed tomography or magnetic resonance imaging. * Must be willing to undergo an incisional or excisional lymph node biopsy of accessible adenopathy or provide the most recent, available archived tumor biopsy. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2. Exclusion Criteria: * Clinical evidence of transformation to a more aggressive subtype of lymphoma or Grade 3B FL. * History of central nervous system lymphoma (either primary or metastatic). * Allogeneic stem cell transplant within the last 6 months, or active graft-versus-host disease following allogeneic transplant or autologous stem cell transplant within the last 3 months before the date of the first dose of study drug administration. * Use of any potent cytochrome P450 3A4 inhibitors or inducers within 14 days or 5 half-lives (whichever is longer) before the first dose of study drug. * Prior treatment with a selective PI3Kδ inhibitor or a pan PI3K inhibitor. * Prior treatment with bendamustine (within 12 months of the start of study treatment). Subjects with prior bendamustine treatment (\> 12 months before the start of study treatment) are eligible if they meet the following criteria: * Did not discontinue because of tolerability concerns. * Achieved either partial or CR to the bendamustine regimen of at least 12 months in duration before relapse/progression. * Experienced progression following a regimen containing an alkylating agent. * Received prior obinutuzumab. * Received rituximab within 4 weeks of study start. * Prior treatment-related toxicities that have not resolved to ≤ Grade 1 before the date of study drug administration except for stable chronic toxicities (≤ Grade 2) not expected to resolve (eg, stable Grade 2 peripheral neurotoxicity). * Received any prior monoclonal antibody (except an anti-CD20 antibody) within 90 days before the date of study start. * History of severe allergic or anaphylactic reactions to monoclonal antibody therapy (eg, subjects in whom re-administration with rituximab would be contraindicated for safety reasons).