Gates Hudson & Associates Inc. has announced plans to develop a 455,000-square-foot office complex adjacent to the Eisenhower Metro Station in Alexandria.

Gateway Metro Center, which will be located at the Telegraph Road and Route 495 interchange, will have five office buildings and one hotel, according to the developer. The office buildings will vary in height from three to nine stories and range in space from 45,000 to 135,000 square feet.

Gateway Metro was designed by Peck & Peck Associates and is owned by Gateway Metro Associates Limited Partnership.

Other recent developments in commercial realty in the Washington metropolitan area:

* The Washington Mortgage Group, a newly formed subsidiary of Washington Bancorp., has leased 5,250 square feet at the Westwood Corporate Center in Tysons Corner.

The mortgage banking firm and Control Video Corp. will be the primary tenants in the ninth building of an 11-building, $140 million office complex developed by the Henry A. Long Co.

* Capital Plaza Mall, the newly renovated $40 million enclosed shopping center near the interchange of Annapolis Road and the Baltimore-Washington Parkway in Prince George's County, will open in the spring, according to a partner of Towne Centre Limited Partnership, the mall's new owners.

* The District of Columbia's Department of Human Services has leased 60,000 square feet at 1300 First St. NE.