Pfizer's Potential Buys, Big and Small

"In our view, improving the revenue and earnings visibility in that period will require aggressive M&A -- including consolidation," Ryan added.

A Pfizer acquisition of Amgen would help wean Pfizer off its Lipitor dependence by adding a significant cancer drug franchise. Pfizer would also gain access to Amgen's star pipeline product, the long-acting osteoporosis drug denosumab, which is already predicted to be a multi-billion-dollar blockbuster but could thrive even more with a Big Pharma-esque marketing push. Last, Pfizer would benefit from Amgen's biologic manufacturing capacity.

Pfizer has begun to make a small push into the antiviral disease market and has one new HIV drug, Selztentry, on the market. An acquisition of Gilead Sciences, the dominant HIV player, would considerably boost Pfizer's standing in the HIV/antiviral treatment market.

A Gilead deal might be considered something "in between" for Pfizer, but "big" could mean another merger of equals, perhaps with Bristol-Myers Squibb, which would boost Pfizer's oncology and HIV programs, or Wyeth, which would help Pfizer add a large vaccines business as well as biologic manufacturing capacity.

Any mega-merger between Big Pharma giants would also bring about big merger cost synergies in terms of general spending and research and development.

In an early December research note to clients following a meeting with Pfizer's CFO Frank D'Amelio, Merrill Lynch (now Bank of America) drug analyst David Risinger said that "we believe Pfizer will be more aggressive with respect to streamlining the company and pursuing more external transaction activities in the future."