Genmab's HuMax-CD20 could be more efficacious than Genentech/Biogen Idec's Rituxan due to the potential for greater activation of immune system defenses, the firm said Dec. 19 after announcing it had reached a codevelopment deal for ofatumumab with GlaxoSmithKline.

"I believe there is a very strong case for differentiation that the antibody does have the chance to be better," Genmab CEO Lisa Drakeman said during a same-day conference call. "One of the things that's really special about HuMax-CD20 is that it was designed to do things that rituximab doesn't."

Like Rituxan, HuMax-CD20 acts on the body's immune system by decreasing certain types of white blood cells that have CD20 on the surface.

However, Genmab said data has shown that it activates immune system defenses more actively than rituximab and other CD20 antibodies. In addition, some patients have responded to HuMax-CD20 who have not responded to Rituxan, the firm said.

Furthermore, Executive VP & Chief Operating Officer Claus Moller-San Pedro said dosing data in oncology and RA shows "that if anything, it seems that it is easier to handle the side effects of ofatumumab" than Rituxan.

HuMax-CD20, a fully human monoclonal antibody, is being studied in chronic lymphocytic leukemia, non-Hodgkin's lymphoma and rheumatoid arthritis. Rituxan is approved for several NHL indications and RA in patients refractory to TNF inhibitors.

"Both GSK and Genmab have committed to a very ambitious development plan in order to bring this product forward on as broad a scale and on as rapid a timetable as possible," Drakeman said.

Genmab announced in June that it was initiating a pivotal study of HuMax-CD20 to treat follicular NHL in patients who fail to respond to Rituxan. The biologic is also in pivotal trials in CD20-positive B-cell CLL and Phase II studies in RA.

GSK and Genmab declined to lay out a development plan for HuMax-CD20 and would not comment on whether head-to-head trials comparing ofatumumab to rituximab will be initiated.

The worldwide development and commercialization deal between GSK and Copenhagen-based Genmab could be worth as much as $2.1 billion.

The deal includes an up-front licensing fee of $102 million, a $357 million equity investment by GSK, additional milestone payments and tiered double-digit royalties on global sales. GSK will equally share development costs for HuMax-CD20 beginning in 2008 and bear sole responsibility for manufacturing and commercial costs.

The deal includes an option for Genmab to copromote Humax-CD20 in a targeted oncology setting in the U.S. and the Nordic region. Exercising that option would also provide Genmab with an option to copromote two GSK oncology products, Bexxar (tositumomab) and Arranon (nelarabine) in the U.S., and nelarabinein the Nordic region (where it is called Atriance ).

"The nice advantage of the sales force is that this is now a first step for us," Drakeman said. "We build a targeted oncology sales force. We learn from our highly capable partner, and as other cancer products come along, we hope that we have a chance to expand our commercial operation."

In addition to gaining rights to HuMax-CD20, GSK will receive rights to any other antibodies with affinity for the CD20 antigen developed by Genmab; the company will also have an exclusive option to CD20 Unibody, which is Genmab's proprietary technology that creates stable, smaller antibodies.

The agreement was signed the same day FDA issued a safety warning regarding Rituxan. The warning concerned two patients treated with the drug for systemic lupus erythematosus that developed progressive multifocal leukoencephalopathy.

Moller-San Pedro downplayed the impact of the warning on ofatumumab. "One of the incidences happened 12 months after the treatment of rituximab, so I think to even conclude something on the basis of the rituximab data or even worse, to try to compare that to Genmab ofatumumab antibody is very premature."

- Jessica Merrill

GSK Licenses Anti-CD20 Agent; Efficacy Relative To Rituxan Touted

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