The board has already kickstarted a formal executive search to identify a new CEO, with an update to be provided in due course.
Simms spent the first period of his tenure battling headwinds after a 2020 Google update de-ranked the company’s portfolio of legacy online casino sites.
However, the acquisition of several US-facing sports betting brands, including Sports Betting Dime, proved the catalyst for a successful turnaround under his leadership.
Last month, shares in the London-listed affiliate group rose by 8% following an announcement that the business grew its net profit more than seven-fold in 2021.
Group revenue grew by 21.2% year-on-year to $66.5m during the 12 months ended 31 December 2021, as the business refocused its strategy on a smaller number of key brands.
Due to its increased focus on North America, the proportion of XLMedia’s total revenue generated by sports betting skyrocketed from 21% in 2020 to 47% in 2021 as the vertical overtook casino as the affiliate’s biggest cash-generating market sector.
XLMedia interim chair Julie Markey said: “I would like to thank Stuart for his contribution through a very challenging period in our history.”
Simms said: “During my time at XLMedia, and with the support of my team, we have been able to deliver substantive, tangible change by de-risking the core business while moving the company’s operational focus towards the growing North American sports market.“This has created a strong asset base capable of delivering shareholder value for many years to come,” he added.
XLMedia interim chair Julie Markey said: “I would like to thank Stuart for his contribution to XLMedia through a very challenging period in our history.
“He departs having expanded our sports footprint in North America, a key strategic focus. I, on behalf of the board, wish him all the very best for the future,” she added.
Markey served as interim chair following the resignation of industry veteran Christopher Bell in January, but the company has now appointed a new non-executive chair.
Marcus Rich joined XLMedia with immediate effect on 31 March. He will become a member of the audit, remuneration and risk committees alongside his duties as the new chair.
Rich has held a number of board positions since 2020, most recently as non-executive chairman of mobile-focused pure play digital media company Digitalbox.
He was also CEO of TI Media, now known as Future, for six years between 2014 and 2020.
Markey said of the appointment: “On behalf of the board, I am delighted to welcome Marcus to XLMedia, who brings a wealth of digital publishing and capital markets experience to this role.
“We look forward to Marcus supporting the strategic ambitions for our business and I believe we will greatly benefit from his knowledge and expertise.”
Rich, former MD of the Mail on Sunday, added: “I am very excited to be joining XLMedia at this important time in its development.
“I am really looking forward to working with the team following the period of strategic redirection to maximise the digital opportunities from the existing assets and take advantage of the growth opportunities in the core areas of sports betting in a marketplace that is constantly evolving.”