The Food and Drug Administration rebuffed plans by NeuralinkElon Musk’s brain technology startup, to conduct human trials on its brain implants, according to a special report published by Reuters Thursday evening.

The news outlet reported that Neuralink, which was founded in 2016, repeatedly missed deadlines for regulatory approval for human trials of its brain implants between 2019 and 2022. 

Despite Musk saying publicly that human trials could start by the end of 2020, during 2021, in 2022, or in 2023, the FDA rejected the company’s application for human trials in early 2022, citing patient safety risks.

Musk said in December that he hoped Neuralink would implant computer chips in the human brain in six months, but the FDA has not given the plan a greenlight.

Reuters noted that rejections from the FDA don’t mean a company won’t be able to eventually obtain approval for conducting human trials but also cited experts who said the pushback signals “substantial concerns.”

“Neuralink doesn’t appear to have the mindset and experience that’s needed to get this to market anytime soon,” Kip Ludwig, former program director for neural engineering at the National Institutes of Health, told Reuters. 

The outlet added that Musk and other Neuralink officials did not respond to requests for comment for the story, while the FDA declined to comment on the company citing agency policy. So far, neither Musk nor Neuralink have spoken publicly about the report since its publication.

In light of its findings, the article has generated plenty of conversation online about Neuralink’s prospects as well as Musk’s track record as a leader since purchasing Twitter late last year.

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This is also the second major Reuters exposé about Neuralink. At the end of 2022, the outlet reported that the company’s testing of a brain implant contributed to the deaths of nearly 1,500 animals over four years and subsequently led to staff outcry.

In an interview with MM+M in December, Paul Root Wolpe, PhD, the Raymond Schinazi professor of bioethics and director at the Center for Ethics at Emory University, said that these reports indicate there’s “such enormous pressure” on Neuralink to move quickly, adding that the animals are “the ones being sacrificed and are suffering.”

When asked about the prospects of the company conducting human trials, Wolpe said scientific validation becomes even more important as it relates to brain devices, especially in light of the reported animal deaths. 

“One article I read said that Musk wants to start human experimentation in six months. Well, that’s going to have to go through human subject protection committees. If I was on that committee, I would be very, very wary of the animal experimentation flaws,” he said.   

In addition to being rejected by the FDA for human trials of its brain implants, the company is also the subject of two separate federal investigations by the Department of Transportation and one by the Department of Agriculture, which began at the behest of a federal prosecutor. 

Despite the public controversies and concerns over the scientific ethics of such technology, the brain implant space has gained significant interest from financiers beyond just Musk in recent years.

In mid-February, Synchron, the brain-computer interface startup backed by Jeff Bezos and Bill Gatesindicated that it is aiming to develop brain implant technology that can help people with paralysis use cursors and home devices through their minds.