* Fmr Sirtex CEO pleads guilty to insider trading - regulator

* Charge relates to 2016 trade before surprise downgrade

* Company had already terminated fmr CEO in 2017 (Adds details on case, background)

SYDNEY, July 3 (Reuters) - The former head of Australian liver-cancer treatment firm Sirtex Medical Ltd has pleaded guilty to insider trading, Australia's corporate regulator said on Wednesday.

Gilman Edwin Wong, who headed the firm from 2005 to 2017, was charged last year after selling 74,698 Sirtex shares in 2016 while in possession of inside information, the Australian Securities and Investments Commission (ASIC) said in a statement.

The sale was made a few months before a surprise earnings downgrade.

Wong entered the plea at a court in Sydney on Tuesday, ASIC said. Insider trading attracts a maximum penalty of 10 years imprisonment and he will be sentenced at a date yet to be set.

Reuters could not immediately find contact details for Wong or his lawyers and Sirtex, which terminated Wong's employment in 2017 after investigating the trades, did not immediately respond to an emailed request for comment.

Sirtex was de-listed in September after accepting a $1.4 billion buyout from a Chinese consortium seeking to import the firm's liver treatment technology.

(Reporting by Tom Westbrook; Editing by Stephen Coates)