I dont think you can put a PE on the earnings because its unliklely to be a good business for more then a year or 2 at most. generics as they come on will eat away - so IMO those earnings will not be given any more then a low single digit multiple - maybe 2x or 3x - think of them almost like you'd treat a one time gain - then take what will be left over in 4 or 5 years - according to rkrw $30m or so is expected in 2 year. I think if you are trying to figure out a realistic target based on that you could do 2x the $300m then do a 10x on the $30m backend.
Change the numbers around as you see fit - I am just pointing out that using a multiple for the essentially one time sales they will have (maybe 2x if it takes 18 - 24 months for Teva) would be IMO erroneous.
So you might get something like $300m x 2 + 30m x 10 and get $900m conservative for Lovenox then you would want to add in some for M118 and Copaxone.