BASEL, Switzerland — Novartis stands to gain exclusive global rights to heart failure drug relaxin through a deal to acquire U.S. biopharmaceutical firm Corthera Inc.

The Swiss pharmaceutical giant said Wednesday that, under the agreement, it plans to acquire all of the outstanding shares of San Mateo, Calif.-based Corthera for $120 million. In addition, Corthera shareholders will be eligible to receive additional payments of up to $500 million depending on clinical milestones, regulatory approval of relaxin and the achievement of commercialization targets.

Pending regulatory approvals, the transaction is expected to close in the first quarter of 2010, according to Novartis.

Relaxin is currently in Phase III clinical trials as a potential treatment option for patients with acute decompensated heart failure. Estimated to affect millions of people in the United States and Europe, the condition is often associated with chronic heart disease where patients typically suffer from severe shortness of breath and the heart’s ability to pump blood from the lungs is impaired, Novartis said. As a result, the lungs become overfilled with fluid, reducing oxygen uptake.

Novartis said that through the acquisition, it would get worldwide rights for relaxin in all countries except Australia and Canada, as well as assume full responsibility for the development and commercialization of the drug, with regulatory submissions in the United States and Europe planned for 2013.

According to the company, the Food and Drug Administration has granted fast-track designation to relaxin as part of its program to expedite the review of new drugs intended to treat serious or life-threatening conditions that can potentially address unmet medical needs.