Inclusion criteria :

          -  Age ≥18 for French patients and Age ≥16 for UK patients

          -  Step A + B : Relapsed / refractory MCL after at least one line of treatment. The
             relapse diagnosis (within 3 months before baseline), needs to be histologically
             confirmed (tumor biopsy or bone marrow biopsy) or confirmed by the presence
             (immunuphenotype) of circulating tumor cells on peripheral blood and/or bone marrow
             aspirate.

          -  Step C : Untreated patients with histologically confirmed MCL (within 3 months before
             baseline). The initial diagnosis has to be confirmed according to WHO classification.

          -  Stage II-IV in need of treatment

          -  ECOG performance status of 0 - 2.

          -  Haematology values must be within the following limits:

               1. Absolute neutrophil count (ANC)≥ 1000/mm3 independent of growth factor support

               2. Platelets ≥75,000/mm3 or ≥ 50,000/mm3 if bone marrow involvement and independent
                  of transfusion support in either situation

          -  Biochemical values within the following limits:

               1. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3 x upper
                  limit of normal (ULN)

               2. Total bilirubin ≤ 1.5 x ULN unless bilirubin rise is due to Gilbert's syndrome or
                  of non-hepatic origin

               3. Serum creatinine ≤ 2 x ULN or estimated Glomerular Filtration Rate (Cockroft
                  Gault 11) ≥ 50 mL/min/1.73m2

          -  HIV, anti-HBc, HbsAg test negative

          -  Life expectancy of more than 3 months.

          -  Women of childbearing potential and men who are sexually active must be practicing a
             highly effective method of birth control during and after the study consistent with
             local regulations regarding the use of birth control methods for subjects
             participating in clinical trials. Men must agree to not donate sperm during and after
             the study. For females, these restrictions apply for at least 30 days after the last
             dose of venetoclax or 18 months after the last dose of obinutuzumab, whichever is
             longer. For males, these restrictions apply for 6 months after the last dose of study
             drug.

          -  Women of childbearing potential must have a negative serum or urine pregnancy test at
             Screening. Women who are pregnant or breastfeeding are ineligible for this study.

          -  Written signed informed consent form.

        Non-Inclusion criteria :

          -  Clinically significant cardiovascular disease such as uncontrolled or symptomatic
             arrhythmias, congestive heart failure, or myocardial infarction within 6 months of
             Screening, or any Class 3 (moderate) or Class 4 (severe) cardiac disease as defined by
             the New York Heart Association Functional Classification.

          -  Major surgery within 4 weeks of inclusion.

          -  Known central nervous system lymphoma.

          -  History of stroke or intracranial haemorrhage within 6 months prior to inclusion.

          -  Requires anticoagulation with warfarin or equivalent vitamin K antagonists (eg,
             phenprocoumon).

          -  Impaired liver, renal (GFR<50ml/min) or other organ function which will interfere with
             the treatment.

          -  Requires treatment with strong CYP3A inhibitors.

          -  Vaccinated with live, attenuated vaccines within 6 months of inclusion.

          -  Known history of human immunodeficiency virus (HIV) or active Hepatitis C Virus or
             active Hepatitis C Virus or active Hepatitis B Virus infection or any uncontrolled
             active systemic infection requiring intravenous (IV) antibiotics. (patients
             HbsAg+and/or antiHBc+ and/or HIV+ are excluded)

          -  Any life-threatening illness, medical condition, or organ system dysfunction which, in
             the investigator's opinion, could compromise the subject's safety, interfere with the
             absorption or metabolism of study treatment (ibrutinib, GA101, GDC-0199) capsules, or
             put the study outcomes at undue risk.

          -  Known hypersensitivity to study treatment (GA101, Ibrutinib, GDC-0199) or to any of
             the excipients.

          -  Known allergy to xanthine oxidase inhibitors and rasburicase

          -  Severe prior reactions to monoclonal antibodies or with prior significant toxicity
             (other than thrombocytopenia) from Bcl-2 inhibitor

          -  History of prior other malignancy with the exception of: Curatively treated basal cell
             carcinoma or squamous cell carcinoma of the skin or carcinoma in situ of the cervix at
             any time prior to study

          -  Other cancers not specified above which have been curatively treated and from which
             subject is disease-free for < 5 years .

          -  Allografted patient

          -  Psychiatric illness or condition which could interfere with their ability to
             understand the requirements of the study.

          -  Pregnancy/lactation

          -  Men or women of reproductive potential not agreeing to use acceptable method of birth
             control during treatment and for 18 months after completion of treatment for the women
             and 6 months for the men.

          -  Use of any standard or experimental anti-cancer drug therapy within 28 days prior to
             the first dose of study drug.