Mylan and Novartis have entered into an agreement which will give the former rights to market a generic version of the breast cancer drug Femara before it comes off-patent.

Terms of the agreement remain confidential but the deal means that Mylan will be able to sell Femara (letrozole) before the first US patents on the drug expire in 2011. The tablet is a big earner for Novartis and US sales for the 12 months ended September 30 reached $470 million.

Mylan was the first company to file a “substantially complete” Abbreviated New Drug Application containing a Paragraph IV certification for the product, which would give it s copycat version 180 days of marketing exclusivity. The agreement is subject to review by the US Department of Justice and the Federal Trade Commission.

The deal is the latest in a growing number of authorised generics agreements being signed. Most recently, AstraZeneca and Teva struck a deal over a copycat version of the former’s asthma drug Pulmicort Respules (budesonide inhalation suspension) and Sanofi-Aventis settled patent infringement suits in the USA with Barr and Teva over the allergy drugs Allegra (fexofenadine) and Nasacort (triamcinolone acetonide).