Enzon Pharmaceuticals Inc. said Monday it is selling most of its business to Italian drugmaker sigma-tau Group and will focus on its experimental cancer drugs and technologies.

Enzon will get $300 million upfront, along with milestone payments of as much as $27 million. Sigma-tau could also pay Enzon royalties on Enzon's four approved drugs through 2014. Sigma-tau is also acquiring a manufacturing facility in Indianapolis in the deal.

Enzon stock reached an annual high of $9.60 on the news. That was its highest price since December 2007.

The specialty drugs sigma-tau is buying are cancer drug Oncaspar, fungal infection treatment Abelcet, meningitis drug DepoCyt, and Adagen, which is used for severe combined immunodeficiency disease, or "Bubble Boy Disease."

In 2008, Enzon announced plans to spin off its biotechnology business into an independent company so it could focus on developing treatments for cancer. It canceled those plans in December due to the weak state of the financial markets. With the specialty drug unit sold, the company said it will focus on potential cancer treatments including the drug candidate Peg SN38.

The transaction, which is subject to financing and approval by Enzon shareholders, is expected to close in the first quarter next year.

In morning trading, Enzon shares rose 43 cents, or 4.7 percent, to $9.41.