Karyopharm Therapeutics Extends Forbearance Period To October 15

As previously disclosed in the Current Report on Form 8-K filed by Karyopharm Therapeutics Inc. (the "Company") on September 11, 2026, the Company entered into a Forbearance Agreement and Limited Waiver to Indentures, dated September 10, 2026 (the "Forbearance Agreement").

On October 13, 2026, in accordance with Section 19 of the Forbearance Agreement, the applicable parties extended the date on which the Forbearance Period (as defined in the Forbearance Agreement) will end, absent earlier termination, from 11:59 p.m., Eastern time, on October 15, 2026 to 11:59 p.m., Eastern time, on October 22, 2026.