David Zaslav will remain at the head of Discovery Communications through the end of 2019, under a new contract unveiled Friday by the Silver Spring, Md., owner of the Discovery, TLC, and Investigation Discovery cable networks.

The move suggests the board of directors of the media company is pleased with Zaslav's performance. His previous deal was set to expire in 2015, according to a Discovery spokeswoman. " He built a strong management team that has expanded the company's reach and relevance, increased its market share domestically and around the world, and created a bigger, stronger portfolio of brands," said r John Malone, Chairman of Liberty Media Corporation and Liberty Global, Inc., and a member of Discovery's board, in a statement. " We look forward to working with David to do more of the same over the next six years."

Zaslav joined Discovery from NBCUniversal in 2007. He had supervised content distribution and struck a range of carriage deals for that company's content, and played a role in the launch of both CNBC and MSNBC. Since his arrival at Discovery, the company has made several strategic international investments, launched new cable outlets including OWN, Velocity, The Hub and Destination America and raised the number of overseas networks carrying its programming to 200 from 100, the company said in a statement Friday.

As part of his employment pact, Zaslav will continue to be a significant long-term shareholder in Discovery Communications. The company said the executive has "committed to hold the majority of his equity from stock grants to term, furthering the alignment of shareholder and management interests."

"I am extraordinarily confident of Discovery's growth prospects for the years ahead," Zaslav said in a prepared statement.

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