British drugmaker GlaxoSmithKline is said to have launched a search for a new CEO to replace Andrew Witty, who is now widely expected to step down at the latest by the end of 2017.

Reports circulating in British financial circles say Philip Hampton, chairman of the GSK board of directors, has informally consulted large shareholders about their preference for a new CEO, with Egon Zehnder, the headhunter who already works on a retainer for GSK, advising on the search in which Witty will be involved.

Hampton, who was elected as chair in 2015, has resisted pressure from some shareholders to force an earlier departure for one of the longest-serving British pharmaceutical chief executives, the daily newspaper Financial Times (FT) said.

Last summer, several large shareholders pressing Witty to step down told the newspaper they would hold back criticism to await developments in a turnaround plan touted by the CEO as bringing about a “fundamental shift” from high-priced prescription drugs toward high-volume vaccines and consumer products.

Along with a sharp downturn in sales and earnings, GSK’s image has been tarnished in the recent past by a corruption scandal in China, though the outlook is generally regarded to have improved in recent months.

While the FT said some investors have urged GSK to look at external candidates such as David Epstein, head of pharmaceuticals at Novartis, others appear to favor internal candidates like Abbas Hussain, head of the company’s pharmaceuticals activities and Emma Walmsley, who runs the consumer healthcare unit.

Others on the short list are said to include Simon Dingemans, chief financial officer and a former Goldman Sachs banker, along with Roger Connor, GSK’s head of global manufacturing and supply chains.

Apart from leadership considerations, some of the drugmaker’s shareholders, notably influential hedge fund titan Neil Woodford, are seen as continuing to push for a break-up of the company’s dual ethical and consumer drugs businesses.

Witty in the past has argued against a break-up, saying the diversified structure is a protection against the risks of drug development.