• Number of patients with treatment-related adverse events as assessed by CTCAE v4.0 [ Time Frame: From the first treatment administration and during treatment period (R-CHOP and blinatomomab) ]
  safety and toxicity of blinatumomab after 2 cycles of R-CHOP
• overall response [ Time Frame: At week 16 from baseline, after blinatumomab induction and at week 24 after blinatumomab consolidation. ]
  Overall response rate (revised Lugano criteria) after the first and second cycle of blinatumomab,
• CR rate [ Time Frame: After blinatumomab consolidation (total of 4 weeks) at week 24 from the beginning of study treatment. ]
  CR rate (revised Lugano criteria) after the second cycle of blinatumomab

Blinatumomab (BLINCYTO) is a bi-specific T-cell engaging (BiTE®) antibody construct that transiently links CD3-positive T cells to CD19-positive B-cells, inducing T-cell activation and subsequent lysis of tumor cells.

The investigators propose to evaluate the efficacy, safety and tolerability of blinatumomab administered after R-CHOP debulking therapy in patients with Richter Syndrome (RS) of diffuse large B-cell lymphoma (DLBCL) histology.

The investigators hypothesize that 8-week blinatumomab induction therapy leads to Complete Response (CR) rate improvement (revised Cheson criteria) from a baseline of 7percent as observed in the prospective study evaluating R-CHOP.

• Drug: RCHOP

  D1 : Rituximab 375 mg/m² IV + Cyclophosphamide 750 mg/m² IV + Doxorubicin 50 mg/m² IV + Vincristine 1.4 mg/m² IV.

  From D1 to D5 : Prednisone 60 mg/m² PO.

• Drug: Blinatumomab
  Blinatumomab by continuous vein infusion

Inclusion Criteria:

• Confirmed diagnosis of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma according to the revised iwCLL criteria19 with biopsy proven transformation to diffuse large B-cell lymphoma, consistent with RS according to the 2016 WHO classification
• Both patients with previously treated or treatment-naïve CLL are eligible
• Age greater than or equal to 18 years
• Eastern Cooperative Oncology Group (ECOG) performance status <3
• Patients must meet the following hematologic criteria at screening, unless they have significant bone marrow involvement of either CLL or RS cells confirmed on biopsy: absolute neutrophil count ≥1.0 G/L, platelet count ≥50 G/L independent of transfusion within 7 days of screening
• Subject must have adequate coagulation, renal, and hepatic function at screening
• Adequate left ventricular ejection function (> 50 %)
• Patients who have undergone prior allogeneic hematopoietic stem-cell transplantation (HSCT) are eligible as long as they do not have significant active graft versus host disease and that their transplant day 0 is > 6 months from their first dose of protocol therapy
• Female patients of child bearing potential must have negative pregnancy test and use an effective method of birth control during treatment period and 48h thereafter; Males must use an effective method of birth control during treatment period and 48h thereafter.
• Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

• Patients with the Hodgkin variant of RS
• Patients with previously treated RS
• History or presence of clinically relevant disorder affecting the central nervous system (CNS)
• Known active DLBCL in the CNS (confirmed by cerebrospinal fluid analysis)
• Steroids treatment (≥ 20 mg for one week) before inclusion
• HSCT within 6 months before inclusion
• Active graft-versus-host disease
• History of other malignancies, except: i) malignancy treated with curative intent and with no recurrence over the last 5 years ii) adequately treated non-melanoma skin cancer without evidence of disease iii) adequately treated carcinoma in situ without evidence of disease
• History of human immunodeficiency virus
• Hepatitis B or C seropositivity (unless clearly due to vaccination)
• Pregnant or breastfeeding women
• Unwilling or unable to participate in all required study evaluations and procedures.
• Unable to understand the purpose and risks of the study and to provide a signed and dated informed consent form and authorization to use protected health information (in accordance with national and local subject privacy regulations)
• Abnormal screening laboratory values as defined as following: a) serum glutamate oxaloacetate transaminase and/or serum glutamate pyruvate transaminase and/or alkaline phosphatase > or =5 x upper limit of normal (ULN); b) Total bilirubin > or = 1.5 x ULN, unless due to Gilbert's disease; c) Creatinine > or = 2.0 x ULN or creatinine clearance <50 mL/min (calculated).
• Fertile male and female patients who cannot or do not wish to use an effective method of contraception during treatment and for 48h after the final treatment used for the purposes of the study
• Treatment with other investigational agent or participating to another trial within 30 days prior to entering the study
• No affiliated to social security