Inclusion Criteria:  Documented CLL/SLL requiring treatment according to iwCLL criteria Age at least 18 years At least one of the following risk factors: 17p-deletion, TP53-mutation or complex karyotype (defined as defined as the presence of 3 or more chromosomal aberrations in 2 or more metaphases.). Life expectancy ≥ six months Adequate bone marrow function indicated by a platelet count >30 x10^9/l Creatinine clearance ≥ 30ml/min Adequate liver function as indicated by a total bilirubin ≤ 2 x, AST/ ALT ≤ 2.5 x the institutional ULN value, unless directly attributable to the patient's CLL or to Gilbert's Syndrome Negative testing for hepatitis B (HbsAg negative and anti-HBc negative; patients positive for anti-HBc may be included if PCR for HBV DNA is negative and HBV-DNA PCR is performed every month until 12 months after last treatment cycle),or hepatitis C (negative testing for hepatitis C RNA within 6 wee ks prior to registration for study screening (i.e. PCR only required when serology was positive)) ECOG (Eastern Cooperative Oncology Group Performance Status) status 0-2  Exclusion Criteria:  Any prior CLL-specific therapies (except corticosteroid treatment administered due to necessary immediate intervention; within the last 10 days before start of study treatment, only dose equivalents up to 20 mg prednisolone are permitted) Absence of high risk disease (17p-deletion, TP53-mutation complex karyotype An individual organ/system impairment score of 4 as assessed by the CIRS definition (e.g. advanced cardiac disease (NYHA class 3 or 4) limiting the ability to receive the study treatment or any other life-threatening illness, medical condition or organ system dysfunction that, in the investigator´s opinion, could compromise the patients safety or interfere with the absorption or metabolism of the study drugs (e.g. inability to swallow tablets or impaired resorption in the gastrointestinal tract) Transformation of CLL (Richter transformation) Malignancies other than CLL currently requiring systemic therapies Uncontrolled or active infection of HIV/PML or any other active infection Anticoagulant therapy with warfarin or phenoprocoumon Pregnant women and nursing mothers