IO Biotech shares fall 66.65% premarket after filing for Chapter 7 bankruptcy and ceasing operations.

IO Biotech dropped 66.65% in premarket trading following the company's filing for Chapter 7 bankruptcy on March 31, 2026, and its subsequent decision to cease operations after exploring strategic alternatives. The development, disclosed in a company filing, triggered a dramatic sell-off as the firm effectively exits the market, leaving no viable operational or financial path forward. The premarket decline reflects investor reaction to the confirmation of the company's dissolution.