The US biotech firm revealed the decision during its recently-released 2006 annual report, and said it was one of a number of initiatives that will allow it to "continue to expand our commercial and clinical production capacity in order to maintain adequate supply to keep up with growing demand for our products."
Amgen said the move is also intended to help "mitigate risks associated with the concentration of our formulation, finish and fill operations in Puerto Rico and adequately prepare to launch a number of our late-stage product candidates".
A company spokesperson told Outsourcing-Pharma.com that its expanded use of third-party contractors was a global company-wide initiative although declined to provide any specific details.
"Amgen is undertaking the largest scale of manufacturing expansion in the biomanufacturing arena and given the speed of growth we are experiencing and the time needed to build and license new manufacturing capacity, we will need to use third parties," said the spokesperson.
Indeed, the other main expansion initiative announced in the report was the building of additional manufacturing capacity at a new site in Ireland, which is to be the firm's first European manufacturing facility, already having four sites in North America and another in Puerto Rico, although the company has been focusing on increasing its presence not only in Europe but globally.
"The most significant of these efforts to increase capacity and reduce concentration are the ongoing construction of our new facility in Ireland and construction of new and expanded bulk and formulation, finish and fill facilities in Puerto Rico," Amgen said in its annual report.
However, in the short time since then, the firm has suddenly put the brakes on its Irish plant plans, announcing last week that it will delay construction of its major new manufacturing plant in Cork by "several years".
Originally due to become operational in 2009 and gain licensing in 2010, the manufacturing facility will now be about three years behind the original schedule, following a "global assessment" of manufacturing needs.
"Our original timeline was very aggressive," a spokesperson for the company told sister publication In-PharmaTechnologist.com.
"We re-assessed our manufacturing capacity needs and found we had more flexibility, and will now be following a more traditional, sequential timeline."
The bulk manufacturing facility is now due to become operational in late 2012, with licensing in late 2013, and the formulation, filling and finishing facilities will be operational in late 2013 with licensing in late 2014.
The plant will have the same capacity, staffing requirements and capital investment (€0.75bn) as originally forecast, and although the company has slowed its plans for the site, the project has by no means ground to halt and development of the site continues.
It remains unclear as to whether third party contractors will be called upon to take up any manufacturing slack during the three year delay until the Cork facility eventually comes on line - the spokesperson refused to comment when asked.