Clinical trials for a new blood cancer drug Arzerra produced by Danish biotech company Genmab in partnership with GlaxoSmithKline (GSK) have proven disappointing.

In clinical trials among patients with non-Hodgkin’s lymphoma only 10% of the population group achieved a reduction in cancer growth, a far lower percentage than expected.

Of a total of 116 patients treated in the study only one complete response was recorded along with eight partial responses.

The results mean that GSK will not be required to make milestone payments to Genmab under the co-development agreement signed by the companies in 2006, which could have risen to $2.1bn (£1.28bn).

GSK, however, is the most likely to lose out as Azerra was expected to serve as the company’s rival to Rituxan, a first-line treatment for blood cancer marketed by Roche and Biogen.

GSK and Genmab are still expected to bring Arzerra to market as a treatment for chronic lymphocytic leukaemia, pending US Food and Drug Administration approval in October 2009.