13D Filing: Delphi Ventures VIII LP and Karyopharm Therapeutics Inc. (KPTI)

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CUSIP NO.   48576U106 13D Page 12 of 12

exhibit A

Agreement of Joint Filing

The Reporting Persons agree that a single Schedule
13D (or any amendment thereto) relating to the Common Stock of Karyopharm Therapeutics Inc. shall be filed on behalf of each of
the Reporting Persons. Note that copies of the applicable Agreement of Joint Filing are already on file with the appropriate agencies.

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