"I can confirm that there was a trade ... which is a very positive outcome for us and gives a direction on where the pricing is going," chief executive Damien Criddle told Reuters by phone.
He declined to reveal details of the trade due to confidentiality, but said it was the first trade during a specified trading time known as the "window" which occurs from 4.30 pm to 5 pm Singapore time on the platform.
Oil pricing agency S&P Global Platts has a similar trading window from 4 pm to 4.30 pm where bids and offers are published and traded, and which helps form its daily assessment for the Japan-Korea-Marker (JKM), currently the main benchmark for the physical spot market in Asia.
The two platforms are part of changes to the normally opaque $230 billion market - which is dominated by fixed, long-term contracts - as sellers and buyers look for increased transparency.
Australia's Woodside Petroleum, which said earlier this month that it had taken an equity stake in Perth-based GLX, was the seller of the cargo on GLX platform, several industry sources said. The buyer could not immediately be confirmed.
A Woodside spokeswoman did not immediately respond to a Reuters request for comment.
GLX was launched in April, 2017 and its first trade was completed in May last year involving Malaysia's Petronas, which also has an equity stake in the platform.
The group said earlier this month that it would start up LNG price indices with energy pricing agency OPIS, a subsidiary of IHS Markit.