A Study to Evaluate Efficacy & Safety of Obinutuzumab, Ibrutinib, and Venetoclax in Richter's Syndrome;

Richter's syndrome (RS) is a life-threatening complication of chronic lymphocytic leukemia (CLL). It is associated with a switch in histopathology and biology, generally with a transformation of the original CLL clone to diffuse large B-cell lymphoma (DLBCL). The development of RS is accompanied by the onset of B symptoms, rapid growth of lymphadenopathy, extra-nodal disease, significant elevations of LDH, and associated multi-organ dysfunction from invasive or obstructive processes.

Previous research has increased general knowledge on the distinct evolutionary patterns of RS and provided a deeper understanding of the risk factors and molecular events predisposing to transformation. However, currently there're main few targetable aberrations and treatment is largely ineffective with a dismal prognosis leaving these patients with a high unmet medical need for better treatment strategies.

RS occurs in 2-10% of CLL patients with an incidence rate of 0.5% per year. The molecular pathogenesis of RS involves inactivation of the TP53 tumor suppressor gene in 50-60% of cases and activating aberrations of NOTCH1 and MYC in about 30% of cases.

These distinct molecular footprints of RS are chemoresistance leading to an aggressive clinical course with low response rates and poor outcomes. Patients with RS are usually excluded from clinical trials and there is no established standard of care in the treatment of RS today.

A number of chemotherapy regimens have been evaluated in the treatment of DLBCL-RS resulting in overall responses ranging between 40%-60% which are short lived with disappointing Progression Free Survival (PFS) and Overall Survival (OS) ranging between 3 - 10 and 6 - 21 months, respectively.

In Israel the current treatment strategy used for newly diagnosed DLBCL-RS is an anthracycline-based regimen, rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). This treatment regimen has shown poor efficacy in a cohort study of 15 DLBCL-RS patients prospectively evaluated by a German CLL study group trial. The ORR was 67% with only 7% Complete Response (CR). The median PFS and median OS were 10 and 21 months, respectively in these patients. In terms of the safety profile of R-CHOP for patients with DLBCL-RS or CLL patients, 15 of the 60 (25%) patients enrolled in this study had therapy discontinued earlier than planned because of the treatment-related toxicity.

Taking into consideration that in addition to the underlying aggressive disease, most RS patients are often at an advanced age and suffer from numerous other comorbidities, therefore only 10%-15% of patient scan undergo the potentially curative allogeneic Hematopoietic Stem Cell Transplantation (HSCT). Additionally, intensive chemotherapy regimens are highly toxic to this population group and lead to excessive treatment-related morbidity. Enrolling DLBCL-RS patients in clinical trials is therefore justifiable, particularly those with RS that is clonally related to the predisposed underlining CLL disease. Due to the poor activity of immunochemotherapy, the possibility of using novel agents in the treatment of RS is of great interest.

The toxicity and the efficacy of the combination of anti-CD20 antibody (e.g. Obinutuzumab or Rituximab) with Ibrutinib and/or Venetoclax have been already reported in both relapsed and naïve patients with CLL. The use of these three agents in combination is highly active in CLL and has manageable side effects. In addition, recent reports showed that treatment with Ibrutinib or Venetoclax as a single drug are active in RS.

Herein the investigators propose a phase 2, open-label, non-randomized, single arm, multi-center study aiming to assess the safety and efficacy with the combination of Ibrutinib, Venetoclax and Obinutuzumab in patients with RS.