When Glaxosmithkline plc’s new CEO, Emma Walmsley, was hiring a “dream team” of executives to lead the company in 2017, former Genentech whizz Hal Barron was the star signing as chief scientific officer. Lured away from Alphabet Inc.’s biotech subsidiary, Calico LLC, by a bumper pay deal, Barron was arguably Walmsley’s most important appointment. Walmsley badly needed a strong leader with credible expertise in science to lead the company’s R&D efforts, as her expertise and experience came from the company’s consumer operation. But as GSK plans to split later this year, Barron is heading for the exit to become CEO of California’s ambitious and enormously well-funded startup Altos Labs Inc.