GlaxoSmithKline (GSK) and Genmab A/S announced top-line results from an international multi-center study of Arzerra (ofatumumab) in rituximab refractory follicular non-Hodgkin's lymphoma (NHL).

A total of 116 patients were treated in the study, including 30 patients treated with 500 mg ofatumumab and 86 patients treated with 1000 mg of ofatumumab. The patients in the study were highly refractory. Forty-nine per cent of patients were refractory to their last chemotherapy treatment. Patients in the study had previously received a median of four prior treatment regimens. The primary endpoint was objective response (International Working Group Criteria) over six months from the start of treatment in the 1000 mg dose population.

The overall response rate (ORR) in the 1000 mg treatment arm was 10 per cent, including one complete response and eight partial responses. In addition, 50 per cent (43) of patients in the 1000 mg treatment arm had stable disease. The overall response rate in the total population was 11 per cent.

The ORR among patients who were refractory to prior rituximab monotherapy (n=27) was 22 per cent. For patients considered refractory to rituximab in combination with chemotherapy the response rate was 7 per cent and among patients considered refractory to rituximab maintenance the response rate was 9 per cent. The median duration of response in the 1000 mg treatment arm was six months and the progression free survival was six months.

There were no unexpected safety findings reported during treatment and within 30 days after last infusion. The most common adverse events (greater than 10 per cent) were rash, urticaria, pruritus, fatigue, nausea, pyrexia and cough.

"The results of this study demonstrate the activity of ofatumumab in patients who had not responded to prior treatment with a CD20 antibody. The response rate in patients refractory to rituximab monotherapy is of interest and warrants further study. We are committed to the further development of ofatumumab in NHL," said Lisa N Drakeman, chief executive officer of Genmab.

"Clearly, this is a challenging patient population to treat with a single agent CD20 antibody. We are committed to evaluating ofatumumab in combination with other agents in this patient population to develop new treatment options for these difficult to treat patients," said Kathy Rouan, vice president and medicines development leader at GSK.

GSK and Genmab continue to review the study results and discuss the development strategy for ofatumumab in NHL.

Ofatumumab is an investigational, fully human monoclonal antibody that binds specifically to the small and large extracellular loops of the CD20 molecule proximal to the cell membrane.