To Evaluate Efficacy and Safety of Parsaclisib Plus Either Rituximab or Obinutuzumab in R/R Follicular Lymphoma (FL) and Marginal Zone Lymphoma (MZL) (CITADEL-302)

Inclusion Criteria:

* Male and female participants aged 18 years or older (Japan, aged 20 years or older).
* Histologically confirmed Grade 1, 2, or 3a FL or nodal MZL, splenic MZL, or extra nodal MZL
* Prior systemic treatment with at least 1 anti-CD20 mAb (either as monotherapy or in combination as chemoimmunotherapy)
* Documented disease that has relapsed or progressed or was refractory after the most recent prior systemic therapy. Note: Participants must not be refractory to anti-CD20 mAb
* Radiographically (CT, MRI) measurable lymphadenopathy per the Lugano criteria for response assessment (Cheson et al 2014).
* ECOG PS of 0 to 2
* Adequate organ functions including hematopoiesis, liver, and kidney
* Willingness to avoid pregnancy or fathering children

Exclusion Criteria:

* Women who are pregnant or breastfeeding.
* Known histological transformation from indolent NHL to an aggressive NHL (eg, diffuse large B-cell lymphoma).
* Presence of CNS lymphoma (either primary or secondary) or leptomeningeal disease.
* Prior treatment with PI3K inhibitors.
* Inadequate washout of immunosuppressive therapy, anticancer medications and investigational drugs.
* Significant concurrent, uncontrolled medical condition, including, but not limited to, renal, hepatic, hematological, GI, endocrine, pulmonary, neurological, cerebral, cardiac, infectious, or psychiatric disease.
* Known HIV infection.
* HBV or HCV infection: Participants positive for HBsAg or anti-HBc will be eligible if they are negative for HBV-DNA; these participants must receive prophylactic antiviral therapy. Participants positive for HCV antibody will be eligible if they are negative for HCV-RNA.
* History of other malignancy within 2 years of study entry.
* Any condition that would, in the investigator's judgment, interfere with full participation in the study.