Question-and-Answer Session
Operator
Thank you. (Operator instructions) Our first question today comes from Michael Yee with RBC Capital Markets.
Michael Yee -- RBC Capital Markets
Hey, thanks. Quick question, just in you're thinking about building up inventory for Cerezyme and Fabrazyme. I know you commented you'll have enough to start treating patients in Q1, but can you talk about how long it would take to build up reasonable levels of inventory such that you wouldn't be running on low levels? Is that something that can be done by mid-2010 or?
Henri Termeer
Yes, to really have the complete redundant inventory available in the system, for that we need the Framingham plant to be approved, and as commented by David, we will start engineering runs in the second quarter I believe of next year, in that plant for Fabrazyme, and then validation runs later in the year, early in 2011. The validation runs will become relevant because they will start then to become the background inventory in the system and we want to build it up to minimally six months to nine months so that we can bridge any kind of interruption of the kind that we've just experienced. So to build for that we need to get Framingham correctly.
And in the meantime during this year, all the products that we will produce in our plant in Allston will go to the global marketplace almost immediately. We will through that effort get some level of inventory in the marketplace, but we don't quite get the background inventory that we insist now on developing the six months to nine months in our own hands to avoid this from this kind of an interruption of creating the kind of difficulty that we had again this year.
Michael Yee -- RBC Capital Markets
Okay, perfect.
Operator
Our next question comes from Geoff Porges with Bernstein.
Geoff Porges - Sanford Bernstein
Thanks very much. I'd like to clarify something, Henri, on your statement in the press release. You expect to fully meet anticipated demand in Q1 for Cerezyme and Fabrazyme. Could you be more specific do you mean for the full quarter or for half of the quarter or by the end of the quarter? And secondly, when you say anticipated demand, is that the demand that you experienced in Q4 '08 or is it demand that is increased or is it demand that's reduced because patients are taking competitors products under treatment INDs? Thanks.
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