Teva Pharmaceuticals has submitted an Abbreviated New Drug Application (Anda) to the US Food and Drug Administration requesting permission to manufacture and market a generic version of Gilead Sciences‘ Viread drug.

In the letter Teva alleges that three patents associated with Viread (tenofovir disoproxil fumarate) owned by Gilead Sciences are invalid, unenforceable and/or will not be infringed by Teva’s manufacture or sale of the product.

Gilead said it is reviewing the ANDA and has 45 days from receipt of the letter to begin a patent infringement lawsuit against Teva.