Asentar for prostate cancer, a potential blockbuster

A tablet designed to emulate the healing power of the sun could be available for the treatment of advanced prostate cancer as early as 2009.

But it remains to be seen whether the drug will be the revolution in prostate cancer care that its makers claim.

The drug, Asentar (DN-101), is based on vitamin D and is given to patients in the advanced stages of prostate cancer along with chemotherapy drugs. Drug makers came up with the idea because vitamin D from sunlight improves the prognosis of certain cancers. But taking natural levels of the vitamin has no effect. Novacea, the company that makes Asentar, produced a novel formulation that reproduces the healing effect without the dangerous side-effects of a vitamin D overdose. If the on-going phase III trial goes to plan, the new drug should be available in 2009, reports Chemistry & Industry, the magazine of the SCI.

‘If the results of the phase III trial are as good as those of the phase II trial, that would be significant,' says Nick James, professor of oncology at the University of Birmingham. In the phase II trials, Asentar significantly improved survival rates, 9 months over patients taking chemotherapy drugs (taxotere) alone. ‘On average, patients in the advanced stage of the disease survive about 18 months, so an extension of 9 months would be very significant in my view,' says James.

Asentar provides levels of vitamin D 50-100 times higher than normal. Patients would be expected to take one tablet once a week with their weekly regime of taxotere for three weeks out of every four.

Business analysts say Asentar is a potential blockbuster, because prostate cancer rates are expected to soar in the next few years. But James is not so sure. ‘A confounding factor is that if you go looking for more cases of cancer, you will find them. But this does not give you an accurate estimate of how many people will go on to develop advanced disease. In fact death rates are going down, which means that the market for this drug is probably pretty static.'

James also points out that it is far from certain that the Phase III trials will repeat the success of early trials. ‘The phase II trial used a less than optimal taxotere regime so the survival rate may have been artificially inflated,' he says. He points out, however, that it may be that the Asentar will eventually prove applicable in the earlier stages of the disease.

Prostate cancer is the second leading cause of cancer death in men. Prostate cancer kills one man every hour in the UK.