The chief executive of Israeli drugmaker Teva Pharmaceutical Industries, Israel Makov, has unexpectedly announced his retirement, prompting a dip in the company’s shares.

Makov will step down next year and be replaced by Shlomo Yanai, aged 55, who is currently employed with an agrochemicals company. Shares in Teva, the world’s largest manufacturer of generic drugs, fell 2% on the surprise announcement as investor expressed concern that Makov had not been replaced with a drug industry veteran.

67-year-old Makov has been instrumental in building up Teva in recent years, masterminding the $7.6 billion takeover of Ivax of the USA which was a key element in elevating the firm to its number one slot. He took over as CEO of the firm in 2002, and since than the firm’s net income has doubled to $1.1 billion last year.