STORY: Elon Musk's brain-implant startup Neuralink is now worth around $5 billion.
That's according to sources close to the matter.
The valuation is based on privately executed stock trades at the firm.
The sources said some buys by bullish investors raised the valuation in recent months.
That came ahead of Neuralink's announcement in late May that U.S. regulators approved a human trial on its brain chip.
An email seen by Reuters showed Neuralink shares were marketed privately to investors in recent days at a $7 billion valuation.
Reuters could not establish whether the seller found buyers at that price.
Neuralink executives and Musk did not respond to requests for comment.
Experts believe it could be years before the firm secures commercial use clearance.
The company also faces other challenges that include federal probes into its handling of animal research.
Musk claims Neuralink's chips could treat obesity, autism, depression and schizophrenia, and even sees them being used for web-surfing and telepathy.