LONDON ¿ Shares in Antisoma Group plc fell by nearly 20 percent after it said the FDA had told it to increase the number of patients in the Phase III trial of its lead product, pemtumomab. The ruling will extend the trial in the treatment for ovarian cancer by 18 to 24 months, delaying the expected launch from 2002 to 2004.

Val Tate, head of investor relations, told BioWorld International, ¿This is clearly very disappointing, but it is not sending out messages on if the company will, or will not, receive approval.¿

The Phase III study of pemtumomab, a yttrium-90 radiolabeled antibody formerly called Theragyn, has recruited its initial target of 300 patients. ¿This is a long-term survival study, designed on the basis of the Phase II data. We agreed the study design with the FDA in October 1997,¿ Tate said.

¿As time has gone on, it has become apparent that the FDA is becoming more cautious; everyone is aware of that. We decided that if we were going to have to alter the study design, now is the time to do it, and that is why we went back to the FDA at this point.

¿Although we argued to be able to continue as before, the FDA said the level of statistical significance should be increased,¿ she said.

The number of deaths required to meet the revised requirement is 116, or 36 more than previously. The number of new patients to be recruited has not been determined. The calculation is complicated by the fact that the safety committee monitoring the trial has indicated that overall mortality for the total study population is lower than had been expected at this stage of the trial.

¿While there is evidence that patients in clinical trials get better standards of care overall, we were quite encouraged by the lower mortality; there could be some very positive messages in that,¿ Tate said.

She said the FDA is helping to redesign the study and recognized the need to bring it to a conclusion.

Pemtumomab is partnered with Abbott Laboratories, which is funding the trial. There is a mechanism in the agreement whereby any additional costs could be apportioned between the partners, but as yet it has not been discussed if Abbott will invoke that clause. The product is also in a Phase II trial in gastric cancer.

Tate said it was not expected that expanding the trial would increase Antisoma¿s cash burn. However, the company, based in London, only has sufficient funding for the next 15 months. ¿We clearly need to raise more money, and the share price has taken quite a knock.¿ It fell 33.5 pence to #1.55 when the news was announced last Wednesday. The company intends to concentrate on bringing in new products to increase its appeal to investors.

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