Background: Transformation of B-cell chronic lymphocytic leukaemia (B-CLL) to diffuse large B cell lymphoma (DLBCL) (Richter's syndrome (RS)) is a rare (2-15% of patients) but catastrophic complication of B-CLL. Dose-intense chemotherapy regimens investigated in small single institution trials, but with the exception of bone marrow transplantation for a minority of patients, little has improved the median overall survival of patients with RS beyond eight months. Patients are often elderly, immunosuppressed, possess co-morbidities and have a deteriorating performance status. TP53 disruption is a common molecular abnormality noted in RS and contributes to the tumour's chemotherapy resistance. Ofatumumab is a fully human anti-CD20 monoclonal IgG1κ antibody that targets a unique epitope on B lymphocytes. It has displayed increased binding affinity and a longer dissociation time when compared to rituximab resulting in improved complement dependent cellular cytotoxicity (CDCC); a mechanism with the potential to overcome apoptosis-resistance in TP53 disruption. Given the prevalence of TP53 disruption in RS, Ofatumumab was considered a relatively non-toxic agent with a sound rationale to test in a prospective multicentre trial as an adjunct to CHOP induction and subsequent ofatumumab maintenance therapy in responding patients.
Methods/design: The CHOP-OR study is a prospective phase II study to evaluate the safety, feasibility and activity of a CHOP chemotherapy in combination with ofatumumab in induction and subsequent maintenance for patients with newly diagnosed RS. The primary objective will be the overall response rate (ORR) in patients with RS after six cycles of CHOP-O. The secondary objectives include feasibility of recruitment, progression free survival (PFS), overall survival (OS) and toxicity. The study will be accompanied by exploratory analysis of the genomic landscape of RS in newly diagnosed patients.
Discussion: The CHOP-OR trial evaluates the safety, feasibility and activity of CHOP plus Ofatumumab induction and Ofatumumab maintenance in new RS patients. The study is currently recruiting and has met the interim analysis criteria, with more than 7 of the first 25 participants achieving a CR or PR after six cycles of CHOP-O. The study has the potential to identify predictive biomarkers for this treatment modality.
Trial registration: NCT01171378.