Amgen‘s (NASDAQ:AMGN) biosimilar drug portfolio will be studied in clinical trials in alliance with clinical research organization PRA.

PRA has entered into a strategic partnership with Amgen to do work on a series of phase 3 studies to develop biosimilar drugs. Biosimilars are follow-on biologic drugs that are cheaper than very expensive biologic drugs.

No financial terms were disclosed, but PRA, based in Raleigh, said the agreement governs the entire scope of Amgen’s global biosimilar portfolio.

The deal is part of the trend of CROs entering strategic partnerships with pharmaceutical and biotechnology companies. The deals typically mean a CRO becomes the exclusive provider for a company’s clinical work. Under the agreement with Amgen, PRA will be the only CRO working on Amgen’s biosimilars.

The companies did not identify specific drugs that would be studied under the partnership. But Amgen late last year entered into a deal with generic drug company Watson Pharmaceuticals (NYSE:WPI) to develop and commercialize biosimilar cancer drugs. The deal calls for Amgen to take the lead in developing, manufacturing and commercializing these oncology biosimilars. Watson will kick in up to $400 million of co-development costs and have a hand in helping in developing and commercializing these products. The partnership won’t be developing biosimilars for Amgen’s proprietary products.

These biosimilar deals come as regulators develop guidelines for biosimilars. The U.S. Food and Drug Administration in February issued draft guidance on biosimilar development. The guidance is important because these biologic products were deemed to be too complex to be covered by regulations that govern generic drugs.