Anglo-Swedish drug giant AstraZeneca has won an additional six months of sales protection for its cancer drug Arimidex, after US regulators agreed to a paediatric patent extension for the drug.

The US Food and Drug Administration’s move will keep Arimidex’ (anastrazole) patent armour in tact until June 2010, so the company will continue to enjoy exclusive sales in the drug’s three licensed indications until then.

Arimidex first hit the market in 1995 after being approved for the treatment of advanced breast cancer in postmenopausal women when the disease continued to progress despite therapy with tamoxifen. In 2000, its use was expanded as a first-line attack for hormone receptor positive or unknown, locally advanced or metastatic breast cancer, and two years later it was given a green light for adjuvant treatment with hormone receptor positive early breast cancer.

The drug is not approved for any use in children but, back in 1999, AstraZeneca began discussions with the FDA to carry out two studies to assess the potential of Arimidex in two paediatric conditions resulting from an increase in oestrogen production: gynecomastia (excessive breast development) in pubertal boys and early-onset puberty in girls with McCune-Albright Syndrome.

No clear benefit
These studies failed to demonstrate a clear benefit with Arimdex over placebo and, consequently, AstraZeneca “will not be seeking an indication in either of these paediatric conditions”, John Patterson, Executive Director of Development at AstraZeneca, explained. However, as the trials were conducted to a certain standard, the company was still awarded a paediatric patent extension by the FDA, a spokesman told PharmaTimes.

Sales of Arimidex in the USA grew 15% to hit $507 million for the nine months of 2007 and, according to the company, with 38.3% of prescriptions the drug holds the lion’s share of the hormonal treatments market. An extra six-months’ worth of full revenues from the product will therefore likely be very welcome news for the drugmaker.