Apogen Technologies Inc., a McLean government contractor, agreed to be acquired by QuinetiQ Ltd., a technology company based in Hampshire, England, for about $300 million in cash.

Under the agreement, which is to be announced today, Apogen will operate as a wholly owned subsidiary of QuinetiQ and will keep its name. Apogen chief executive Todd A. Stottlemyer and Chairman Philip A. Odeen will remain in those positions.

"The partnership allows us to continue to differentiate ourselves in the market, especially against companies that just provide services, because [QuinetiQ] has this treasure trove of technologies," Stottlemyer said.

Apogen was founded in January 2004 when ITS Services Inc., of Springfield, merged with Science & Engineering Associates Inc. of New Orleans. The privately held company has 900 employees and, according to Stottlemyer, posted $205 million in revenue last year.

QuinetiQ -- pronounced like "kinetic" -- was created in 2001 out of what was previously a British defense research agency. It commercializes technologies developed in defense labs and has 12,000 employees.

QuinetiQ has been expanding rapidly in the United States. On Monday, another QuinetiQ subsidiary, Waltham, Mass.-based Foster-Miller Inc., acquired Planning Systems Inc., a Reston technology firm, for $42 million. QuinetiQ also has a partnership with Washington private equity firm, the Carlyle Group. Glenn A. Youngkin, a managing director at Carlyle, sits on QuinetiQ's board of directors.

Stottlemyer said Apogen will continue to hire, and look for companies to acquire.

The companies plan to close the deal next month and expect no layoffs as a result of the acquisition.