UPDATE 3-Roche hit as FDA seeks more data on arthritis drug

* U.S. regulators ask for more data on Actemra

* Do not require more clinical studies

* Roche hepatitis C drug approved in Europe

* Stock falls 1.9 pct, underperforms sector index

(Adds analyst comment, updates shares)

By Katie Reid

ZURICH, Dec 4 (Reuters) - U.S. approval for Roche Holding AG's (ROG.VX) Actemra has been delayed further after regulators asked for more non-clinical data on the potential blockbuster rheumatoid arthritis drug.

The Swiss group said on Thursday the Food and Drug Administration (FDA) had requested additional animal model data but had not ordered further clinical studies, and that the company would submit the required information in the third quarter of next year.

By 0900 GMT, Roche stock had fallen 1.9 percent to 165.90 Swiss francs, underperforming a 1.2 percent rise in the DJ Stoxx healthcare index .SXDP.

"Roche is likely to be weaker today. If so, we'd use it as a buying opportunity. We think Actemra remains highly likely to get U.S. approval," said Collins Stewart analyst James Knight.

The FDA wants confirmation that Actemra does not affect peri- and post-natal development and fertility, and Roche has also been asked to put together a risk evaluation to ensure the drug is prescribed properly.

The FDA had initially asked for more information on Actemra in September, delaying approval for the drug, sales of which could potentially be worth over 1 billion dollars a year.

Actemra is approved in Japan where it is sold by Roche's partner, Chugai Pharmaceutical (4519.T). Roche said Swiss authorities had also approved the drug on Wednesday but it had yet to access markets in the United States and the rest of Europe.

HEPATITIS C APPROVAL

Basel-based Roche had mixed news on another drug, Pegasys for treating hepatitis C, saying on Thursday the European Commission had approved Pegasys for patients whose first round of treatment had not been successful. [ID:nL4619982]

A study in New England Journal of Medicine, however, found that long-term Pegasys therapy did not reduce the rate of disease progression in patients with chronic disease and advanced fibrosis.

Actemra is an anti-interleukin-6 receptor antibody and works in a different way to the existing class of medicines that block an inflammatory protein called tumour necrosis factor (TNF).

Roche believes Actemra will become an important alternative treatment to established anti-TNF drugs, helping diversify its business and reduce reliance on cancer medicines.

It will compete against Roche's own established medicine, Rituxan, which is already given to existing anti-TNF drug non-responders. Citigroup analysts see sales of the product reaching 714 million Swiss francs ($654 million) by 2012.

Roche says rheumatoid arthritis -- characterised by inflammation of the membrane lining joints throughout the body, which can cause pain and stiffness and, ultimately, disability -- is thought to affect 21 million people worldwide. (Addtional reporting by Emma Thomasson in Zurich and Ben Hirschler in London; Editing by Simon Jessop)