European regulators adopted a new guideline on so-called biosimilar antibody drugs on Friday, paving the way for cheaper copies of multi-billion-dollar medicines for cancer and other serious diseases.

As expected, the European Medicines Agency (EMA) did not publish the full document after it was endorsed by its committee of experts, but said it would be released on its website "shortly."

A spokeswoman told Reuters earlier this week that publication could take a couple of weeks.

The new rules are keenly awaited by drug companies and investors, who want to know how difficult - and hence expensive - it will be to win approval in Europe for copies of complex antibody-based drugs.

The EMA gave nothing away on Friday, saying merely: "This guideline lays down the non-clinical and clinical requirements for monoclonal antibody-containing medicines claiming to be similar to another one already marketed."

Many industry experts expect a cautious approach, requiring separate clinical trials for different diseases addressed by the same antibody. That would be good news for original producers of monoclonal antibodies, like Roche and Amgen.

For makers of generic drugs, it would push up costs and may limit the field to a few sophisticated and well-funded companies like Teva, which is working on biosimilars with Lonza; Novartis unit Sandoz; and Hospira.