Exhibit 31.2
CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER PURSUANT TO RULE 13a-14(a)/15d-14(a) PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1934, AS AMENDED
I, Justin A. Renz, certify that:
1. I have reviewed this Quarterly Report on Form 10-Q/A (Amendment No. 1) of Karyopharm Therapeutics Inc.;
2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.
| /s/ Justin A. Renz |
| Justin A. Renz |
| Executive Vice President and Chief Financial Officer |
| (Principal financial and accounting officer) |
Date: November 14, 2014