Neuren shares fell when Europe knocked back its treatment for a rare childhood disease, then jumped when the regulator changed its mind. Here’s how it played out. Shaw and Partners’ Adam Dawes used it on Switzer TV to show how a single decision can be the whole story for a biotech. Neuren’s drug treats Rett syndrome, a rare neurological disorder that mostly affects young girls, at a rate of about one in 10,000. For a company like Neuren, one regulator’s yes or no can move the whole share price.