Uber Technologies Inc. co-founder Travis Kalanick will resign from the ride-hailing company's board of directors, effective Dec. 31.

Kalanick is leaving to "focus on his new business and philanthropic endeavors," the company said Dec. 24.

The former CEO recently sold more than 90% of his holding in the company. The share sales equate to more than $2.5 billion of Uber stock, the Wall Street Journal reported.