Novartis has begun a mid-stage study for a biosimilar of Roche's blockbuster monoclonal antibody Rituxan/MabThera.

The Swiss major's generic unit Sandoz said the Phase II trial for its version of Rituxan (rituximab) is focusing on patients suffering for rheumatoid arthritis. The drug is also approved  for other conditions, including non-Hodgkin's lymphoma.

Sandoz says that over the past few years it has developed "a robust, high-yield and large-scale process for the production of biosimilar rituximab" at its facilities in Schaftenau, Austria. To ensure biosimilarity with the reference product, "a comprehensive physico-chemical and functional analysis of the product was conducted using modern bioanalytic techniques, followed by further studies". Data so far suggest that its version is "highly similar to the reference product, justifying initiation of clinical studies in patients".

Rituxan is a huge earner for Roche, and Novartis says it ranks among the top three biologics worldwide, with 2009 sales of $5.60 billion. Sandoz boss Jeff George noted that this "key development milestone" demonstrates that the firm is on track to maintain its global leadership position in biosimilars in the medium to long term. 

He added that with "nearly 50% market share within the global regulated biosimilar market, and with three marketed products, Sandoz plans to continue to broaden patient access to essential high-quality biologics". Ameet Mallik, head of Sandoz Biopharmaceuticals, noted that "our pipeline is particularly focused on mAbs, the largest and fastest-growing segment of the biologics market".

Other companies are working on a biosimilar of Rituxan, notably Teva Pharmaceutical Industries, while last week Spectrum Pharmaceuticals signed a pact with Viropro to develop a version of rituximab ahead of its US patent expiration in 2015.