LONDON- Private equity-backed cyber security firm Avast is targeting a market capitalisation of between 2.5 billion and 3.2 billion pounds ($3.5-4.5 billion) in its initial public offering (IPO), potentially the biggest London listing since July.

The bookrunner announced a price range of between 250 pence and 320 pence a share on Thursday, aiming to sell around 25 percent of the company and raise about $200 million in proceeds from the issue of new shares.

The market admission will take place on May 10, the bookrunner said.

The London Stock Exchange is working to attract more technology IPOs, usually more drawn to New York. Sophos SOPH.L is the only other cyber security firm listed in Britain.

In 2017, Avast's adjusted revenue was $780 million and adjusted cash earnings before interest, tax, depreciation and amortisation (EBITDA) was $451 million.

With net debt of around $1.35 billion, the enterprise value of the company could be up to $5.9 billion after the offering.

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, with Summit Partners holding 7 percent.

Morgan Stanley and UBS are global coordinators for the offering.

The listing is expected to be the biggest by market capitalisation in London since July when the floatation of Russian gold company Polyus PLZL.MM gave it a 6.3 billion pound market value.

($1 = 0.7193 pounds)

(Reporting by Dasha Afanasieva; Editing by Mark Potter) ((dasha.afanasieva@tr.com; +44 (0) 20 7542 0214;))