(Reuters) - Former shareholders of Good Technology Corp, a mobile software maker, are suing JPMorgan Chase & Co <JPM.N> for breach of fiduciary duty, according to a lawsuit filed on Thursday.

JPMorgan was "self-interested" and "conflicted" in its dealings with Good Technology, which led the start-up to sell itself to BlackBerry Ltd <BB.TO> <BBRY.O> in 2015 at a "fire-sale" price of $425 million, the shareholders said in the amended lawsuit filed in Delaware Chancery Court.

Good Technology was being advised by JPMorgan at the same time as the investment bank was advising BlackBerry, according to the lawsuit. JPMorgan prioritized its relationship with BlackBerry over its dealings with Good Technology, the complaint said.

The lawsuit valued Good Technology at over $1 billion.

Blackberry and JPMorgan were not immediately available to comment on the issue.

The New York Times first reported the amended lawsuit earlier on Thursday. The complaint is part of a suit Good Technology shareholders originally filed in October 2015.

The suit already named Good Technology directors and executives as defendants and accused them of conflicts of interest.

The case is Good Technology Corporation Stockholder Litigation, Court of Chancery, State of Delaware C.A. No. 11580-VCL

(Reporting by Andrew Hay)