First PacTrust Bancorp, the Chula Vista holding company for Pacific Trust Bank, said it entered into a definitive agreement to purchase all the outstanding stock of Gateway Bancorp, the holding company of Cerritos-based Gateway Business Bank, with $187 million in assets, the bank said June 6.

The aggregate cash price for the deal is about $17 million. With the acquisition, First PacTrust would have more than $1 billion in total assets, with 14 branches, the bank said.

In addition to retail offices in Lakewood and Laguna Hills, Gateway has a mortgage banking unit with 22 loan production offices in California, Arizona and Oregon.

First PacTrust CEO Greg Mitchell said the transaction, which is expected to close in the second half of the year, will broaden the bank’s reach into Orange County and expand its Los Angeles market. Last month, the bank announced plans to open two offices in the LA area, in Santa Monica and Century City.

Mitchell said the transaction will be immediately accretive to the bank’s tangible book value and earnings.

In early trading June 6, shares of First PacTrust, traded under FPTB on Nasdaq, were up 45 cents or nearly 3 percent to $15.85. Its 52-week range is $6.80 to $16.68.

— Mike Allen