Karyopharm Therapeutics, a clinical-stage biotech developing treatments for cancer and other major diseases, filed on Friday with the SEC to raise up to $80 million in an initial public offering. The Natick, MA-based company, which was founded in 2008, plans to list on the NASDAQ under the symbol KPTI. Karyopharm Therapeutics initially filed confidentially on September 5, 2013. BofA Merrill Lynch and Leerink Swann are the joint bookrunners on the deal. No pricing terms were disclosed.