Twitter lost two executives today: Chief Technology Officer Adam Messinger tweeted that he’s leaving after five years at the social media company, saying he plans to “take some time off.” And VP Product Josh McFarland, who has been at the company for about two years, will head to investment firm Greylock Partners in the spring. Twitter brought him aboard when it paid $500 million for his company, TellApart, which collects data to help advertisers target messages to different consumers.

The departures are the latest of several this year as Twitter tries to figure out ways to reinvigorate its growth — and stock price, which has declined 22.6% in 2016.

In January, Jason Toff — a former YouTube exec who ran Vine’s New York operation — left to work on Google’s virtual reality ventures. Last month, COO Adam Bain, formerly with Fox Interactive Media, left.

In addition, in October Twitter said it was slashing its workforce by 9% in a restructuring and would discontinue shortform video service Vine.

“Twitter is a challenged company with stalled user growth,” Wedbush Securities’ Michael Pachter said when Bain left. It “needs a substantial change in its user interface, needs to convince non-users of the value of its service, and needs to convince a substantially greater number of advertisers that they can derive value from reaching Twitter’s audience.”