Efficacy and Safety Study of Idelalisib in Participants With Indolent B-Cell Non-Hodgkin Lymphomas

Key Inclusion Criteria:

* Karnofsky performance status of ≥ 60 (Eastern Cooperative Oncology Group \[ECOG\] performance score of 0, 1, or 2)
* Histologically confirmed diagnosis of B-cell iNHL, with histological subtype limited to the following:

  * Follicular lymphoma (FL)
  * Small lymphocytic lymphoma (SLL) with absolute lymphocyte count \< 5 x 10\^9/L at the time of diagnosis and on baseline laboratory assessment performed within 4 weeks prior to the start of study drug administration
  * Lymphoplasmacytic lymphoma (LPL), with or without associated Waldenstroms Macroglobulinemia (WM)
  * Marginal zone lymphoma (MZL) (splenic, nodal, or extranodal)
* Prior treatment with ≥ 2 prior chemotherapy-based or immunotherapy-based regimens for iNHL
* Presence of radiographically measurable lymphadenopathy or extranodal lymphoid malignancy
* Prior treatment with rituximab and with an alkylating agent (eg, bendamustine, cyclophosphamide, ifosfamide, chlorambucil, melphalan, busulfan, nitrosoureas) for iNHL
* Lymphoma that is refractory to rituximab and to an alkylating agent
* Discontinuation of all other therapies for treatment of iNHL ≥ 3 weeks before Visit 2
* For men and women of childbearing potential, willingness to abstain from sexual intercourse or employ an effective method of contraception during the study drug administration and follow-up periods
* Willingness and ability to provide written informed consent and to comply with the protocol requirements

Key Exclusion Criteria:

* Central nervous system or leptomeningeal lymphoma
* Known histological transformation from iNHL to diffuse large B-cell lymphoma
* History of a non-lymphoma malignancy except for the following: adequately treated local basal cell or squamous cell carcinoma of the skin, cervical carcinoma in situ, superficial bladder cancer, localized prostate cancer, other adequately treated Stage 1 or 2 cancer currently in complete remission, or any other cancer that has been in complete remission for ≥ 5 years
* Evidence of ongoing systemic bacterial, fungal, or viral infection (excluding viral upper respiratory tract infections) at the time of initiation of study treatment
* Pregnancy or breastfeeding
* Ongoing alcohol or drug addiction
* Known history of drug-induced liver injury, chronic active hepatitis B infection, chronic active hepatitis C infection, alcoholic liver disease, non-alcoholic steatohepatitis, primary biliary cirrhosis, ongoing extrahepatic obstruction caused by stones, cirrhosis of the liver, or portal hypertension
* History of prior allogeneic bone marrow progenitor cell or solid organ transplantation
* Ongoing immunosuppressive therapy, including systemic corticosteroids. Participant may be using topical or inhaled corticosteroids.
* Prior therapy with idelalisib
* Exposure to another investigational drug within 3 weeks prior to start of study treatment
* Concurrent participation in another therapeutic treatment trial
* Prior or ongoing clinically significant illness, medical condition, surgical history, physical finding, ECG finding, or laboratory abnormality that, in the investigator's opinion, could affect the safety of the participant, alter the absorption, distribution, metabolism or excretion of the study drug, or impair the assessment of study results

Note: Other protocol defined Inclusion/Exclusion criteria may apply.