UPDATE 1-Genmab, Glaxo cancer drug beats target in key test

(Adds Genmab CEO interview, M&A speculation, background)

By Ben Hirschler

LONDON, July 31 (Reuters) - An experimental treatment for leukaemia being developed by Danish biotech company Genmab (GEN.CO) and GlaxoSmithKline (GSK.L) has proved effective in a pivotal Phase III trial, the companies said on Thursday.

Genmab Chief Executive Lisa Drakeman told Reuters the result demonstrated ofatumumab's potential to become a multibillion-dollar seller. It could reach the market as early as mid-2009, she said.

The antibody drug met its goal in the study of difficult-to-treat patients with chronic lymphocytic leukaemia (CLL), producing a response rate well in excess of the 25 percent minimum needed.

"We hoped that we would be better than the 25 percent, which was the primary endpoint, and we've just gone way beyond that and it's very, very exciting," Drakeman said in a telephone interview.

An objective response rate of 51 percent was achieved in patients who were "refractory", or failed to respond, to the existing treatments of fludarabine and Campath.

Campath, or alemtuzumab, is an antibody drug for leukaemia from Bayer BAYG.DE and Genzyme GENZ.O.

A second group of patients refractory to fludarabine and for whom Campath was inappropriate because of their bulky tumours, saw an objective response rate of 44 percent.

The positive results seen from the 138 patients clears the way for the new medicine -- the most important product in Genmab's pipeline -- to be submitted to U.S. and European regulators for approval as early as this year.

"We could hope to be on the (U.S.) market by about the middle of next year, if we were to file near the end of this year," Drakeman said.

"We believe it has multibillion-dollar (per year sales) potential and I feel even more strongly about that after today."

She hopes ofatumumab will get to European market in 2009.

BIOTECH M&A

Glaxo bought global rights to ofatumumab, also known as HuMax-CD20, in a December 2006 deal worth up to $2.1 billion -- a record sum for a biotech product agreement at the time.

The drug, which is also in trials for non-Hodgkin's lymphoma, rheumatoid arthritis and multiple sclerosis, is similar to MabThera/Rituxan from Roche (ROG.VX) and Genentech DNA.N.

Drakeman declined to comment on speculation that Genmab might be a takeover target in a consolidating biotechnology sector, which has recently seen a spate of deals.

A growing number of biotech companies are being snapped by their larger partners in the pharmaceuticals sector.

Bristol-Myers Squibb (BMY.N) on Thursday offered to buy ImClone Systems IMCL.O in a deal valuing its partner at $5.2 billion.

And last week, Roche (ROG.VX) offered $43.7 billion for the part of Genentech Inc DNA.N it does not already own, while Sanofi-Aventis (SASY.PA) agreed to buy Acambis (ACM.L) for 276 million pounds.

Genmab has a market value of more than $2 billion. (Editing by Andy Bruce)