Regulatory advisors in the US have refused to back GlaxoSmithKline’s Avodart and Merck's Proscar - medicines used to treat enlarged prostates - for the prevention of prostate cancer in men.

GSK has submitted an application for approval to market Avodart (dutasteride) for prostate cancer prevention, following clinical data showing that the drug could cut the risk of the disease.

Merck & Co, on the other hand, has requested permission to add information from a clinical trial indicating that Proscar (finasteride) can prevent prostate cancer to the drug’s prescribing information.

However, after assessing the data an advisory panel to the US Food and Drug Administration has concluded that the drugs’ benefits do not outweigh their risks in this patient population, and thus has effectively barred their use for this particular indication.

While clinical trials have demonstrated a reduction in overall risk of prostate cancer in patients taking Avodart or Proscar, it was mainly the development of so-called low-grade cancers being prevented. Moreover, the data also showed a small increase in the number of patients developing aggressive cancers in the treatment arms versus placebo group, giving rise to uncertainty over the medicines’ benefit-risk ratios.

“Whilst we are disappointed by the Committee’s conclusions on dutasteride as a prostate-cancer risk-reduction therapy, it is important to note that dutasteride has an established efficacy and safety profile in the treatment of BPH, including trials involving 10,000 men and the cumulative of 5.5 million years of patient exposure,” noted GSK’s Anne Phillips, vice president, medicine development leader, Oncology Research and Development.

More setbacks for GSK

Elsewhere at GSK, the company said it has received a Complete Response letter from the FDA regarding its marketing application for Potiga (ezogabine), an investigational antiepileptic being assessed for the adjunctive treatment of adults with partial-onset seizures.

GSK and partner Valeant are evaluating the letter “in which FDA cited non-clinical reasons for this action”, and the firms said they believe the items - the specific nature of which have not been disclosed - can be addressed sometime next year.

Earlier this year, the agency’s Peripheral and Central Nervous System Drugs Advisory Committee has voted unanimously to recommend approval of Potiga, after concluding that the risk of urinary retention risk that has been associated with the drug “could be mitigated by patient monitoring”.

And last but not least, GSK has also announced the death of the clinical programme for its experimental ‘red wine’ drug SRT501 in patients with the blood cancer multiple myeloma.

Following the suspension of a II study of the drug earlier this year after some patients developed kidney problems, the drug giant has dumped the programme because of limited efficacy and safety issues, a spokeswoman confirmed yesterday, according to media reports.