Klarman's Kleryx holding transitions into stake in fully integrated kidney care company with investor's approval. : Seth Klarman is head of the highly successful hedge fund The Baupost Group LLC. Photographer: Jeenah Moon/Bloomberg© 2018 Bloomberg Finance LP disclosed Thursday that his long-term stake in kidney care company Keryx Biopharmaceuticals closed as it converted into a stake in Akebia Therapeutics upon the merger of the two companies. Klarman’s Baupost portfolio contained 25,791,678 shares of Keryx at third-quarter end, equating to a 21.4% stake in the company.