U.K.-based Horizon Discovery Group PLC said Jonathan Milner was stepping down from its board.
Milner, who had been on the gene-editing services provider's board for a decade, is leaving to "free more time to concentrate on my other interests."
As of May 15, Milner owned about 7.25% of Horizon Discovery and 10.21% of British biotech company Abcam Plc.
Abcam recently dropped its bid to acquire Horizon Discovery for £270 million, an unsolicited proposal that Horizon said undervalued the company.
Milner was not involved in the discussions for the proposal.