Inclusion Criteria:

• Subjects with a diagnosis of CD20 and CD22-positive, follicular lymphoma, who have received 1 or 2 prior regimens, at least 1 of which should have contained administration of rituximab (either as a single agent or in combination).
• Age 18 years or older,
• ECOG performance status ≤ 2,
• ANC ≥ 1.5 x 10^9/L (1500/mL) and platelets ≥ 75 x 10^9/L (75,000/mL), serum creatinine ≤ 1.5 x ULN and urine protein to creatinine ratio of ≤ 0.5, total bilirubin ≤ 1.5 x ULN, AST and ALT ≤ 2.5 x ULN.
• At least 1 measurable disease lesion that is ≥ 1.5 cm x 1.5 cm by CT or MRI, in an area of no prior radiation therapy, or documented progression in an area that was previously irradiated.

Exclusion Criteria:

• Subjects with clinical evidence of transformation to a more aggressive subtype of lymphoma or stage 3B follicular lymphoma.
• Subjects whose disease is rituximab refractory, meaning that they did not have a CR or PR, or that they experienced disease progression within 6 months from the initiation of the rituximab or rituximab containing treatment regimen administered immediately preceding study enrollment.