RA Capital Management Establishes 9.9% Stake in Karyopharm Therapeutics Inc.

On April 2, 2026, RA Capital Management, L.P., along with Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund, L.P., filed a Schedule 13G disclosing a new 9.9% ownership stake in Karyopharm Therapeutics Inc. (KPTI). The reporting persons beneficially own 2,078,913 shares of common stock. This position was established following a private placement that closed on March 26, 2026. The Fund directly holds 1,917,354 shares of common stock, plus pre-funded and common warrants. However, the exercise of these warrants is subject to a 'Beneficial Ownership Blocker,' which prevents the reporting persons from owning more than 9.99% of the outstanding common stock. Consequently, the reported 2,078,913 shares represent the maximum number of shares currently issuable under these constraints. RA Capital serves as the investment adviser to the Fund, with Dr. Kolchinsky and Mr. Shah acting as controlling persons. The filing includes a standard certification that the acquisition was not intended to influence or change the control of the issuer.