Let's take a look at today's top stories in biotech and health care. Keep an eye out for Allergan (UNKNOWN:AGN.DL), AstraZeneca plc (NYSE:AZN), Pfizer (NYSE:PFE), and Valeant Pharmaceuticals (NYSE:BHC).

Valeant makes a play for Allergan
Allergan shares are up double digits this morning after news hit the Street that Valeant Pharmaceuticals has made a tender offer to buy the company for roughly $46 billion. Valeant shares are also up over 5% in trading as of this writing.

Per the terms of the proposal, Valeant would pay $48.30 in cash and 0.83 shares of its own stock for every share of Allergan. The math works out to be about $14.4 billion in cash and $32 billion in Valeant stock. If this deal goes through, it would bring together the biggest eye and skin-care drug portfolios in the industry. The deal is reportedly backed by activist hedge fund manager Bill Ackman, who owns close to 10% of Allergan.

Allergan has said it is willing to review the tender offer from Valeant, but a deal may not be a foregone conclusion. Jefferies is reporting this morning that Allergan may instead pursue the acquisition of Shire plc or perhaps Jazz Pharmaceuticals as a means to ward off a takeover bid by Valeant. While I am dubious about how those deals would create enough synergy between the companies to justify an acquisition, Jefferies is suggesting that Allergan's board and some of its key investors may not be interested in the proposal. Put simply, this could be a smoke screen to buy Allergan more time. So, stay tuned!

Will Pfizer continue its pursuit of AstraZeneca?
On Easter Sunday, a rumor started that Pfizer was interested in buying the struggling pharma giant AstraZeneca for over $100 billion. Although this rumor has yet to be confirmed by either company, AstraZeneca has reportedly rebuffed the offer, despite its declining revenues due to some of its top-selling drugs coming off patent protection. Even so, AstraZeneca shares rose over 8% on this news and Pfizer shares also ended the day in positive territory.

Today, there is a report that Pfizer may make another offer for AstraZeneca as the company wants to bulk up its oncology portfolio through an acquisition. While AstraZeneca has some intriguing early-stage oncology candidates, it is not generally known as a leader in this area. In fact, AstraZeneca has only recently made a handful of deals with the likes of Horizon Discovery and Amplimmune to bolster its weak oncology pipeline. As a result, AstraZeneca's most compelling cancer therapies are in the early stages of their development. As such, I am not convinced a deal would be based on this aspect of AstraZeneca's developmental or commercial pipelines. In other words, I can't see Pfizer paying $100 billion mostly to gain access to some early-stage cancer therapies, when it could probably buy a dozen smaller companies for way less money.

Overall, I think this deal makes sense mostly because of the cost savings it would create, especially in terms of the tax issues Pfizer is facing with repatriating some of its income.