LONDON ¿ Xenova Group plc said its lead compound, XR9576 for the prevention of multidrug resistance in cancer, will go into a pivotal Phase III study, following positive data from the first of three ongoing Phase IIa studies.

CEO David Oxlade told BioWorld International, ¿This is genuinely the most significant event in the company¿s 13-year history. This is a product with very significant commercial potential, and it is the first drug in pivotal studies which has been wholly developed by our scientists in Slough. In addition, it may be the first of three drugs we have in the clinic this year.¿

Several possible protocols have been drawn up for the Phase III trial. ¿We are now in the process of deciding which represents the best overall proposition,¿ he said. ¿There are many different ways this product could be evaluated, and our experts are evaluating the best and shortest way.¿

The trial is expected to start by no later than the fourth quarter, but before it does Xenova has to work out how it will be financed. ¿We have got more cash than forecast, but it is not enough to go through pivotal studies,¿ Oxlade said. Although a partnership is possible, Xenova¿s share price has risen in recent weeks, and Oxlade favors a fund-raising. ¿I think the interests of shareholders are best served by retaining full, unfettered commercial rights. The increase in value between finding a partner now or at the end of Phase III is very significant indeed.¿ While royalty rates of around 20 percent are the norm at the end of Phase II, partnerships sealed after Phase III are likely to secure rates of 30 percent to 50 percent.

Up to 90 percent of cancer patients are estimated to develop resistance to common cytotoxics, which are pumped out of the cancer cell by the action of the P-glycoprotein pump. XR9576 modulates the action of this pump mechanism. The Phase IIa program for the drug is studying its effects in combination with three widely used cytotoxics: paclitaxel, vinorelbine and doxorubicin. The purpose of the study is to assess the degree of interaction, if any, between XR9576 and the cytotoxic drug.

The first Phase IIa study to complete, involving 12 ovarian cancer patients who had previously been treated with a variety of cytotoxic drugs, showed no interaction between XR9576 and paclitaxel. Full results of the study will be published later this year. The Phase I study showed that intravenous or orally administered XR9576 was well tolerated at all doses and produced virtually complete inhibition of the P-glycoprotein pump.