Discover Financial Services posted better-than-expected quarterly earnings on Thursday as loan losses grew less than anticipated and the sixth-largest U.S. credit card issuer trimmed costs.

Net income for the fiscal third quarter, ended August 31, was $577.4 million, or $1.07 per share, compared with $180.1 million, or 37 cents per share, a year earlier.

The latest results included a after-tax gain of $287 million related to an antitrust settlement with Visa and MasterCard .

Excluding the one-time gain, the Riverwoods, Illinois-based company posted a profit of 52 cents per share. On that basis, analysts had expected a loss of 12 cents per share, according to Reuters Estimates.

Discover's charge-off rate -- loans it does not expect to be repaid -- climbed to 8.39 percent in the third quarter from 7.79 percent in the second quarter but was well below rates at its bigger rivals.

Discover shares rose 2.93 percent to $15.77 in premarket trading.

(Reporting by Juan Lagorio; editing by John Wallace)