Strong US momentum and a growing pool of top-spending customers drove sales and profit at Mytheresa in the fourth quarter despite “a very tough market,” said CEO Michael Kliger.

The luxury e-tailer’s North America business grew 40.8 percent in the three months ending June 30, following a ramp-up in marketing investment in the region with special events for clients.

Mytheresa said the value of goods sold (GMV) on its platform rose 14.5 percent to €855.8 million ($912.3 million) for the full year ending June 30, while revenue rose 11.4 percent to €768.6 million. Adjusted EBITDA was up 40.3 percent to €41.1 million.

Shares were up 16 percent in early trading.

Mytheresa’s focus on courting luxury’s wealthiest customers is helping mitigate the impact of broader slowdown in demand for luxury goods, said Kliger, as aspirational shoppers pull back on spending amid an uncertain economic backdrop, hitting peers like Farfetch hard. This is particularly true in the US, a market where luxury companies including LVMH, Kering and Burberry have reported weakening demand.

Mytheresa has ramped up investment in the US to drive brand awareness, staging a five week pop-up in partnership with Flamingo Estate in East Hampton, NY over the summer. It’s also dialled up the number of money-can’t-buy experiences for top clients in the market, hosting events in cities like LA, Nashville, Miami and Aspen.

”We have clearly benefited from our brand being more familiar to target customers,” Kliger told BoF.

Over the past three years, Mytheresa has more than doubled its top customer base, a co-hort that now drives 40 percent of total revenues, the company said. The platform’s average order value on the platform has also reached a new high this year of €654, as top spenders splurge on pricer items.

However, the Kliger remains wary of the outlook for the coming year.

”There is continued uncertainty. So, when looking at the remainder of the calendar year, we remain cautious,” he said. “I think this Christmas, business will be very tough.”