Spectrum Pharmaceuticals has signed a letter of agreement with Viropro to develop a biosimilar version of Genentech / Roche’s monoclonal antibody drug rituximab.

The deal seeks to capitalise on patent expirations for Rituximab, which achieved worldwide sales of about $5.6 billion in 2009.

Biosimilars, also known as follow-on biologics, are officially-approved versions of biopharmaceutical products made by a different company following patent and exclusivity expiry of the innovator product.