He became the first publicly announced employee of the exchange in February 2019.
Kellner is the former CEO of Instinet, LLC. He was appointed CEO of Instinet March 6, 2014, replacing Fumiki Kondo, who was named head of Nomura Asset Management’s overseas client division in Tokyo. 
He was previously head of Instinet's Americas businesses.
Before that, Kellner held a variety of positions at Nomura, including managing director for US equity and global portfolio sales and trading. Kellner has also held senior trading and technology positions at Charles Schwab & Co, Investment Technology Group and Morgan Stanley.
Kellner holds a bachelor of science degree in mechanical engineering from the University of Michigan.
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