The Food and Drug Administration issued written approval on Thursday expanding enrollment in Neuralink's PRIME study to fifteen additional participants, as the trial's first patient demonstrated a consistent typing rate of 40 words per minute using neural signals alone across a two-month evaluation period that an independent review team confirmed was accurately reported.
The FDA's written approval cited a clean safety record across the trial's current participants and demonstrated device functionality as the basis for clearing the expanded enrollment. No incidents of device migration, infection, or serious adverse events had been reported across any of the implanted participants. The agency set conditions for the expansion including mandatory monthly safety reports and a six-month review before any further expansion could be considered.
The 40-words-per-minute result represents a typing speed that many individuals achieve with a physical keyboard, accomplished here through neural signals alone by a participant with a spinal cord injury that prevents the use of their hands. Neuralink's chief executive described the result as "a proof point, not a ceiling" in remarks accompanying the announcement. An independent review team that examined all 47 test sessions from the two-month evaluation period confirmed that the median performance had been accurately reported. "They chose to report the median, not the peak," one of the independent reviewers said. "The best single session was 47 words per minute. The company chose the more conservative number. That is the right scientific choice."
Patient advocacy organisations representing people with ALS, spinal cord injury, and stroke — the primary conditions targeted in the expanded trial enrollment — welcomed the news. "For people who have lost the ability to communicate through physical movement, 40 words per minute through a neural signal alone is transformative," said the executive director of one ALS patient organisation. "This is why we support this research. We need it to work."
Two additional participants are reported to be progressing through the device calibration phase with performance above initial projections. A fourth implant is scheduled for later this month. The expansion to fifteen more participants will provide a substantially larger dataset and will test whether the early performance and safety record is representative across a wider range of participants and conditions.
The 15-participant expansion does not constitute commercial authorisation. The PRIME study remains an early-stage clinical trial subject to ongoing FDA oversight. Results from the expanded cohort are expected to inform a future application for broader authorization.
Neuralink said participants in the expanded cohort would include individuals with ALS, spinal cord injury, and stroke, reflecting the range of conditions in which brain-computer interface technology is being evaluated as a potential communication and mobility tool.