On Tuesday, Baxter International Inc said that it has agreed to buy two drugs to treat a rare form of blood cancer from Italian drugmaker Sigma-Tau Finanziaria SpA for $900 million, before expenses.

Both the drugs are biologics for the treatment of acute lymphoblastic leukemia (ALL) and will form part of Baxter's biopharmaceutical business Baxalta, which is expected to be spun off this year.

On Tuesday, Baxter said that out of the two drugs, Oncaspar has been given the approval for sale in the United States, Germany and Poland and has around $100 million in annual sales. The other drug is presently undergoing trials.

The US Food and Drug Administration have classified ALL as a rare disease. The American Cancer Society has estimated that around 6,250 new cases of ALL will be diagnosed in 2015.

Treatments for rare diseases have always attracted interest from drugmakers and high premiums for their developers as the therapies can command exceptionally high prices with little pushback from the limited number of patients.

Biologics, which are made from living cells, carry hefty price tags as they have safer profiles and stronger efficacy as compared to typical treatments for cancers and immunological diseases.

It is expected that Baxter's deal will close in the third quarter and add to its adjusted profit on a cash basis in the first full year after that.

There are many other drugmakers that are presently developing treatments for ALL, including Novartis AG, Bristol-Myers Squibb Co, GlaxoSmithKline Plc, Genmab A/S and Roche AG.

Baxter shares saw a little change at $69.16 in early trading on Tuesday on the New York Stock Exchange.