Your post is misleading. You're not providing counter-evidence for the 'failure for decades' claim, and are in fact confirming the 'one of the first' part.
Yes, it has been approved, but only very recently, in late 2012. It is also the first such drug that has been approved (and to date, the only one), and this happened under 'exceptional circumstances'. The usual standard of supporting evidence was forgone because the disease it treats is so rare. The company is explicitly required to supply further supporting evidence, and the rules for its use are very strict.[1]
Yes, it has been approved, but only very recently, in late 2012. It is also the first such drug that has been approved (and to date, the only one), and this happened under 'exceptional circumstances'. The usual standard of supporting evidence was forgone because the disease it treats is so rare. The company is explicitly required to supply further supporting evidence, and the rules for its use are very strict.[1]
[1] http://www.drugs.com/uk/glybera.html