LONDON (Reuters) - Cyber security firm Avast AVST.L shares were down 2.6 percent in early trade on Thursday in the London Stock Exchange's biggest debut in almost a year.

The logo of Avast Software company is seen at its headquarters in Prague, Czech Republic, April 12, 2018. REUTERS/David W Cerny

Priced at 250 pence per share, the private equity-backed firm was trading at 243.5 pence as of 0801 GMT.

Bankers typically price initial public offerings (IPOs) aiming for a slight rise in the first days of trading.

The company had set the offer at the bottom end of its guidance, having already reduced the expected price range, in a market in which scores of IPOs have been canceled.

The offer size of $816.6 million included gross proceeds of approximately $200 million and represented around 25 percent of the shares of the company. It was the biggest IPO on the LSE since July 2017.

Based on the offer price, the company had a market capitalization of 2.4 billion pounds.

Avast is 46 percent-owned by its founders, Czech entrepreneurs Pavel Baudis and Eduard Kucera.

CVC Capital Partners [CVC.UL] has a 29 percent stake and Summit Partners hold 7 percent.

In 2017, Avast reported adjusted cash earnings before interest, tax, depreciation and amortization (EBITDA) of $451 million on adjusted revenue of $780 million.

Morgan Stanley MS.N and UBS UBSG.S led the transaction.