Novel therapies unveiled at ASCO
drug companies from around the world keen to showcase their new
therapies.
This year's American Society of Clinical Oncology (ASCO) conference is taking place between 1-5 June in Chicago, US, and there are several novel drug candidates on show. Two investigational drugs that cut off the blood supply to tumours and so could prevent it from growing and spreading were singled out for special mention by the organisers. Dr Dean Bajorin of the Memorial Sloan-Kettering Cancer Center, New York, said: "Our understanding of the molecular basis of cancer continues to expand and with that knowledge comes a growing number of targeted therapies that attack cancer cells while leaving healthy cells intact." The first novel treatment option highlighted at the event was a study that showed Regeneron's VEGF-Trap therapy is useful to treat patients with ovarian cancer that has returned and is resistant to platinum-based chemotherapy drugs. VEGF-Trap is comprised of portions of the extracellular domains of human VEGF receptors R1 and R2 (also called FLT-1 and KDR), fused to an antibody. The resultant fusion protein binds to VEGF-A and neutralises it, thus preventing angiogenesis. Other VEGF blocking drugs include: Genetech's Avastin (bevacizumab), which was approved by the US Food and Drug Administration in 2004 for use in colon cancer; kinase inhibitors like Bayer's Nexavar (sorafenib), co-developed with Onyx Pharmaceuticals, and Pfizer's Sutent (sunitinib). Epithelial ovarian cancer makes up 85 to 90 per cent of the approximately 22,000 cases of ovarian cancer diagnosed in the United States each year. This Phase II trial is the first in this indication and preliminary results show that tumours shrank in 8 per cent of patients and stopped growing in 71 per cent. "The results of this study are very promising," said Dr William Tew, from the Memorial Sloan-Kettering Cancer Center. "Most anti-angiogenesis drugs have been studied in combination with other chemotherapy agents. "There are only a handful of diseases for which these drugs seem to work as a single agent, and ovarian cancer-because of its high dependence on blood vessel growth in order to spread-seems to be one of them. As a result, VEGF-Trap shows potential for patients who have developed resistance to other chemotherapy agents." A second drug that is causing a stir at the meeting is Pfizer's axitinib (AG-013736). It is a small molecule inhibitor of vascular endothelial growth factor (VEGF) receptors 1, 2 and 3, which play a role in tumour formation by promoting the growth of blood vessels. The first Phase II trial to evaluate the experimental drug in patients with advanced thyroid cancer has shown that the drug has substantial anti-tumour activity. There have been no new drugs for this type of cancer in around 30 years and only 30 per cent of patients who fail on standard therapy survive five years. "Axitinib and other VEGF inhibitors represent an exciting new front in the treatment of advanced thyroid cancer," said Dr Ezra Cohen, assistant professor of medicine at the University of Chicago and the study's lead author. "As recently as three years ago we had very little to offer these patients, and now we're seeing response rates at a level we've never seen with chemotherapy." This latest research showed the tumour shrank - by 31 to 68 per cent - in 22 per cent of patients, with the effect lasting between one and 16 months. The tumour stopped growing in a further 50 per cent of patients. The target of the drug was confirmed by blood tests, which showed lower levels of VEGF receptors 2 and 3, by 32 per cent and 35 per cent respectively.
