Digital health and fitness company OliveX has acquired Zombies, Run! developer Six to Start in a deal worth up to $9.5 million. 

The deal will see OliveX hand over an initial $6.65 million in cash and shares, followed by an additional $2.85 million based on certain performance targets. 

Based in the UK, Six to Start creates fitness-focused audio stories and gaming experiences including The Walk and Zombies, Run! -- the latter of which has an average 300,000 active users per month and roughly 50,000 paid subscribers.

OliveX, meanwhile, develops a range of fitness apps and products including Kara Smart Fitness, a subscription-based mobile app that offers a variety of workouts, classes, and training programs.

As part of the purchase, Six to Start founder and CEO Adrian Hon has been appointed chief innovation officer at OliveX, though he'll also continue to oversee Six to Start as executive director. 

OliveX chief exec Keith Rumjahn said the company was excited by Six to Start's growth potential and "loyal subscriber base."

"With average revenues per paid subscriber exceeding £25 a year, and with real growth potential, Six to Start will bring immediate value to OliveX," commented Rumjahn in a press release. "Most importantly though we see enormous benefit in their global, loyal, subscriber base and the team’s product design and monetization expertise."