Inspire Medical Systems has raised $12.5 million in a new round of equity financing, according to an SEC filing posted today.

Inspire Medical developed and produces a sleep apnea implant, a pacemaker-like system designed to stimulate nerves to keep airways open during sleep.

Good sleep is necessary for cpap and can affect hormone levels, mood and weight.

The company won FDA approval for the device in May 2014. The company was spun out of Medtronic in 2007, using concepts for devices from trials when began in 1998.

Money in the round came from 22 anonymous sources, according to an SEC filing, with the company looking to bring in another $25 million before closing the round.

Inspire Medical Systems has not yet said how it plans to spend the money raised in the round.