experimental treatment not Superior to standard - no need to continue the follow-up

This study is designed to investigate:

• the interest of a new monoclonal antibody (GA101)versus rituximab
• the interest of PET to identify early responders

Patients will receive either rituximab (standard treatment), either GA101 (study treatment), according to the randomization arm.

The monoclonal antibody will be associated to a chemotherapy: CHOP or ACVBP according to site's choice.A PET scan will be done before inclusion, after 2 chemotherapy cycles, and after 4 chemotherapy cycles, to identify early patients responders, for who consolidation with ASCT is not required.

Inclusion Criteria:

• Histologically proven CD20+ diffuse large B cell lymphoma (WHO Classification)
• Baseline PET scan available with at least one hypermetabolic lesion
• Aged ≥ 18 years and ≤ 60 years
• Eligible for autologous stem cell transplant
• Patient not previously treated
• Age adjusted International Prognostic Index (aa-IPI) equal to 1, 2 or 3
• Life expectancy ≥ 3 months
• Negative HIV, HBV (anti-HBc negativity) and HCV serologies before inclusion
• Having signed a written informed consent
• Having ability and willingness to comply with study protocol procedures
• Men must agree to use a barrier method of contraception during the treatment period and until 3 months after the last dose of GA101 or rituximab, or ACVBP14 or CHOP14 chemotherapy, whichever is longer
• Women of childbearing potential must agree to use an adequate method of contraception, such as oral contraceptives, intrauterine device, or barrier method of contraception during the treatment period and until 12 months after the last dose of GA101, Rituximab, ACVBP14, or CHOP14 chemotherapy, whichever is longer

Exclusion Criteria:

• Any other histological type of lymphoma
• Any history of treated or non-treated indolent lymphoma. However, patients not previously diagnosed and having a diffuse large B-cell lymphoma with some small cell infiltration in bone marrow or lymph node may be included
• Central nervous system or meningeal involvement by lymphoma
• Contra-indication to any drug contained in the chemotherapy regimens
• Poor cardiac function (LVEF < 50%) on echocardiogram or MUGA scan
• Poor renal function (creatinine level > 150*mol/l or clearance < 30ml/min), poor hepatic function (total bilirubin level > 30µmol/l, transaminases > 2.5 X maximum normal level) unless these abnormalities are related to the lymphoma
• Poor bone marrow reserve as defined by neutrophils < 1.5 G/L or platelets < 100 G/L, unless related to bone marrow infiltration
• Any history of cancer during the last 5 years, with the exception of non-melanoma skin tumors or stage 0 (in situ) cervical carcinoma
• Any serious active disease (according to the investigator's decision)
• Treatment with any investigational drug within 30 days before planned first cycle of chemotherapy
• Pregnant or lactating women
• Adult patient under tutelage
• Prior history of Progressive Multifocal Leukoencephalopathy (PML)