PFS was defined as the interval from randomization to the earlier of the first documentation of definitive disease progression or death from any cause. PFS (months) = (minimum (date of disease progression, date of death) - date of randomization + 1)/30.4375.

Progression-free survival was defined as the interval from randomization to the earlier of the first documentation of definitive disease progression or death from any cause. Definitive disease progression was CLL progression based on standard criteria (other than lymphocytosis alone) as defined by the 2008 update of the International Workshop on CLL guidelines, ie, appearance of any new lesion; increase by ≥ 50% in the sum of the products of the perpendicular diameters of measured lymph nodes (SPD); new or ≥ 50% enlargement of liver or spleen; transformation to a more aggressive histology (eg, Richter's or prolymphocytic transformation); reduction in the number of blood cells (cytopenia) attributable to CLL.

The overall response rate (ORR) was defined as the proportion of participants achieving complete response (CR) or partial response (PR) based on IWCLL 2008 criteria.

An AE was any untoward medical occurrence in a clinical study participant which did not necessarily have a causal relationship with the treatment. An AE can therefore be any unfavorable and/or unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. TEAEs were defined as 1 or both of the following: 1) Any AEs with an onset date on or after the study drug start date and no later than 30 days after permanent discontinuation of study drug; and/or 2) Any AEs leading to premature discontinuation of study drug.

An AE was any untoward medical occurrence in a clinical study participant which did not necessarily have a causal relationship with the treatment. An AE can therefore be any unfavorable and/or unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. TEAEs were defined as 1 or both of the following: 1) Any AEs with an onset date on or after the study drug start date and no later than 30 days after permanent discontinuation of study drug; and/or 2) Any AEs leading to premature discontinuation of study drug.

Treatment-emergent laboratory abnormalities were defined as values that increase at least one toxicity grade from baseline. If the relevant baseline laboratory value was missing, then any abnormality of at least Grade 1 observed within the time frame specified above was considered treatment-emergent.The most severe graded abnormality from all tests was counted for each participant. Treatment-emergent laboratory abnormalities were graded per Common Terminology Criteria for Adverse Events (CTCAE), Version 4.03 where 1=Mild, 2=Moderate, 3=Severe, 4=Potentially Life Threatening.

An AE was any untoward medical occurrence in a clinical study participant which did not necessarily have a causal relationship with the treatment. An AE can therefore be any unfavorable and/or unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. TEAEs were defined as 1 or both of the following: 1) Any AEs with an onset date on or after the study drug start date and no later than 30 days after permanent discontinuation of study drug; and/or 2) Any AEs leading to premature discontinuation of study drug.

Lower limit of quantitation was 5 ng/mL for idelalisib and metabolite GS-563117 both.