Giving evidence to the Commons Public Accounts Committee, Mr Parsa denied he was sacked.

BBC: Ali Parsa

Ali Parsa, Circle chief executive, has announced he is stepping down to become a non-executive director.

BBC: Cambridgeshire

Chief executive Ali Parsa will be replaced by Steve Melton, who will serve on an interim basis.

BBC: Hinchingbrooke: Ali Parsa steps down as chief executive

"This is the ultimate personalized medicine, " says Dr. Andrew Parsa, the neurosurgeon who is running the trial.

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Mr Parsa will remain on the board of Circle as founder and a non-executive director, the company said.

BBC: Hinchingbrooke: Ali Parsa steps down as chief executive

But Circle chief executive Ali Parsa said he was confident his firm would make a success of it.

BBC: NHS 'must be tougher negotiator' on private deals

At the time, Mr Parsa said it was too soon to judge whether the contract had been a success.

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Ali Parsa last week said he was stepping down as head of Circle.

BBC: Ali Parsa

Parsa, at UCSF, says his hospital tested 14 patients for the multicenter study.

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The company said the main reason for Mr Parsa to step down was to give him more time to fulfil "his passion for social entrepreneurship".

BBC: Hinchingbrooke: Ali Parsa steps down as chief executive

But Ali Parsa, Circle's chief executive, worries that the requirements imposed by Monitor, the health regulator, on those seeking to compete with NHS services have now become so demanding that only a state-backed company or very large private group could satisfy them.

ECONOMIST: NHS reform