Medical company ElectroCore has expanded its series A round to $50m as it prepares to submit its migraines and cluster headaches device for regulatory approval.

US-based medical company ElectroCore raised $50m in a series A round on Tuesday from backers including Merck Global Healthcare Innovation Fund, pharmaceutical company Merck’s corporate venturing affiliate.

Merck was joined by venture capital firms Easton Capital and Core Ventures. The round was over subscribed by $10m, after the investors decided to add to the initial $40m round, raised in April 2013. The company initially raised $500,000 in seed funding in November 2012.

ElectroCore develops non-invasive and non-pharmacologic therapies to treat…