Biotech behemoth Amgen (NASDAQ:AMGN) got a little bigger this week following a pair of acquisitions. On Monday, the drugmaker paid $420 million to acquire privately-held Ilypsa; and yesterday, Amgen acquired another private biotech, Alantos Pharmaceuticals, for $300 million.

The all-cash deals for both companies gives Amgen several mid-stage drug candidates to beef up its drug pipeline. Ilypsa's lead compound is set to start phase 3 trials as a treatment for a side effect of chronic kidney disease. Alantos' lead drug is a DPP-4 inhibitor used to treat diabetes. DPP-4 inhibitors are one of the hottest new therapies in treating diabetes since the approval of Merck's (NYSE:MRK) future blockbuster Januvia in October of last year.

Other major drugmakers like Bristol-Myers Squibb (NYSE:BMY) and Novartis (NYSE:NVS) are also engaged in the race to market the next DPP-4 inhibitor. The market for these compounds to treat diabetes will be big enough to support several approved drugs.

At the rate that it's buying biotechs out, Amgen should have more than half the sector under its control by the end of the year. All jokes aside, Amgen has been a serial biotech acquirer in the past years, with deals like its $2 billion Abgenix buyout in 2005 and the monster $17 billion Immunex deal in 2001.

Since Ilypsa and Alantos were privately held, there's not a lot of public information about the companies floating about. Alantos' diabetes drug could very easily become a blockbuster depending on its efficacy and safety profile compared to the other DPP-4 inhibitors. But until the compounds from these deals are more mature in their developments, it's difficult to say whether Amgen is effectively using its capital with these acquisitions. As with other acquisitively-minded drugmakers, though, investors should closely follow the success or failure of the compounds from these deals to be sure that Amgen isn't squandering money that just as easily could be going to them via dividends.

Looking for further Foolish drug stock coverage? Check out the Fool's market-beating Rule Breakers newsletter. You can check out all our recommendations as well as get access to our message boards and exclusive content with a 30-day free trial.

Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy.