He will transition from his current roles to become a non-executive director at GSK on Aug. 1. Replacing him as chief scientist and R&D head will be Tony Wood, who came to GSK from Pfizer in 2017 and currently serves as senior vice president of medicinal science and technology.

GSK said its board of directors conducted an “extensive” search process and interviewed both internal and external candidates before selecting Wood to succeed Barron.

“Tony has been a key partner to Hal in delivering our R&D approach, and with his experience and expertise across science, data and new technologies, he is perfectly placed to build on Hal’s outstanding progress and to deliver value from our pipeline,” Walmsley said in a statement.

Barron was one of several high-profile executive hires Walmsley made soon after becoming GSK’s CEO in 2017 with a mandate to shake up the drugmaker, which had missed the first wave of cancer immunotherapy breakthroughs and lagged in other key areas.

Yet, while GSK has won approval for notable new medicines like the multiple myeloma treatment Blenrep under their leadership, investor pressure hasn’t abated. In 2020, the last year for which full-year sales are available, GSK reported about 24 billion pounds in drug and vaccine revenue, roughly the same as what it earned a decade earlier.

The company’s top drug then was the asthma medicine Advair, which booked more than 5 billion pounds in yearly sales at its peak. The subsequent loss of patent protection in the U.S. dragged GSK’s revenue down heavily, and attempts to replace those sales through new treatments haven’t all panned out.

Meanwhile, GSK largely missed on an opportunity to showcase its expertise in vaccines during a once-in-a-century pandemic, as it opted against developing its own COVID-19 shot and partnerships with Sanofi and CureVac hit setbacks and delays.

Calls for change have grown in recent months, primarily from activist investors Elliott Advisers and Bluebell Capital Partners. Elliott, in particular, has pointed to declining R&D spend and share price underperformance compared with GSK’s pharma peers as reasons to add biotech veterans to the board.

While Elliott has not openly sought to oust Walmsley, the firm called for GSK’s board to begin a leadership selection process for GSK and its consumer health joint venture with Pfizer, which the companies plan to separate from this year. (GSK has recently rebuffed several attempts by Unilever to buy the consumer business, including a December 20 offer worth 50 billion pounds.)

An Elliott spokesperson said Wednesday the company has no comment on Barron’s departure.

Several other GSK executives have left in recent months, including Axel Hoos, who led the company’s cancer drug unit, and Emmanuel Hanon, chief of vaccines research.

When Barron steps down from his GSK roles in August, he’ll take the reins at Altos Labs, a biotech startup that officially launched Wednesdaywith a high-powered list of executives and a staggering $3 billion in initial funding.

Joining Barron at the new company are Rick Klausner, Altos’ cofounder who will serve as chief scientific officer; former Grail and Juno Therapeutics CEO Hans Bishop, another cofounder who will become Altos’ president; and Genentech veteran Ann Lee-Karlon, Altos’ chief operating officer.

Altos says it aims to reverse disease through studying cellular rejuvenation and is backed by a board of directors that includes the Nobel laureates Jennifer Doudna, Frances Arnold and David Baltimore.

Note: This story has been updated to include mention of Unilever’s bid to buy GSK’s consumer health joint venture with Pfizer, as well as other executive departures from GSK.