Years, approval was Sept 2009 and WP tried to get AMAG to buy Allos in 2011 which didnt go through. Now they are trying to get Spectrum to buy Allos which is currently in the works.
Looks like the deal happened @ April 5th, 2012 for $1.82 in cash and one Contingent Value Right (CVR) per share, given certain criteria were met. Spectrum bought them for $206 million.
In Oct. 2011 prior to the Spectrum deal, another deal was stuck with AMAG Pharmaceuticals to buy Allos for $195 million and $2.44 per share. Shareholders sued, and Allos settled, forgoing the deal which opened the doors for Spectrum.