Inclusion Criteria

1. Histologically confirmed relapsed or refractory indolent non-Hodgkin's lymphoma (NHL)
2. Any stage (Ann Arbor staging, Appendix 15.7), with or without B symptoms
3. CD 20+ lymphoma (confirmed by immunochemistry)
4. Measurable disease.
5. Atleast 1 prior therapy.
6. Age ≥ 18 years
7. Life expectancy of at least 3 months
8. ECOG performance status (PS) of 0 or 1
9. Adequate cardiac function defined as LVEF ≥ 50% by MUGA scan
10. Adequate renal function
11. Adequate hepatic function
12. Adequate bone marrow function
13. Recovery from all acute toxicities from prior therapies (except alopecia and grade 1 peripheral neuropathy).

Exclusion Criteria

1. Prior treatment with a cumulative dose of doxorubicin equivalent exceeding 450 mg/m2
2. Radiotherapy, chemotherapy or other therapies for NHL within 4 weeks of treatment start
3. Systemic corticosteroids to treat NHL within 5 days prior to first dose of study treatment.
4. Radioimmunotherapy (RIT) within 3 months of treatment start
5. Known hypersensitivity to the excipients or the study drugs that the patient will receive
6. Known Type I hypersensitivity or anaphylactic reactions to murine proteins or to any component of rituximab
7. Major thoracic and/or abdominal surgery in the preceding 4 weeks, from which the patient has not fully recovered (patients who have had minor surgery and one week's recovery period may be enrolled)
8. HIV-related lymphoma
9. Active CNS involvement
10. Clinically significant cardiovascular abnormalities
11. Serious (NCI CTCAE grade 3-4) intercurrent infection at randomization, infection requiring oral antibiotics, or deep-seated or systemic mycotic infections.
12. Investigational study drug within 30 days before randomization. Patient must have recovered from all side effects of other investigational therapy.
13. Clinical symptoms suggesting unresolved HIV, HBV or HCV infection. .
14. History of another malignancy except: curatively treated basal cell or squamous cell skin cancer, in situ cervical cancer, adequately treated stage I or II cancer from which the patient is currently in remission, or any other cancer from which the patient has been disease-free for 5 years
15. Pregnant or lactating women
16. Potentially fertile men and women and their sexual partners not willing to use adequate contraception as defined by the Investigator during the study and for 6 months after the last day of study drug administration