Publicis Groupe SA  (PUBGY) shares fell the most in nearly a year after the world's third-largest advertizing firm posted softer-than-expected third quarter sales and avoided reiterating previous targets for profit margins next year.

The group said sales in the three months ending in September rose 1.2% to €2.26 billion ($2.66 billion), a stronger reading than in the prior quarter but still shy of analysts' forecasts of €2.3 billion. However, despite a solid 3% rise in North American revenue, new CEO Arthur Sadoun didn't endorse 2018 profit margin targets left by his predecessor, Maurice Levy.

"We are only in the middle of our transformation journey, as it is a profound change, in a highly volatile market," Sadoun said. "That is why, even though we have some preliminary encouraging signs, we remain very cautious and determined to win."

"We are convinced that we have an unparalleled position in the market through both our ability to help clients with marketing transformation and digital business transformation," he added. "We are committed to achieving our transformation which will put us in a position to drive a significant improvement in organic growth and financial performance."

Publicis shares were marked 6.45% lower by mid-day in Paris, the steepest fall since October of last year, and changing hands at €58.18 to extend their year-to-late loss to just over 11%.

Levy's 2018 margin target of between 17.3% and 19.3% looks increasingly difficult to achieve for Sadoun, who replaced the industry veteran earlier this year, given that the group only recorded a 13.2% tally in the first half of this year.

Organic sales in Europe, which fell 1.5%, and ongoing weakness in China, which pushed Asia Pacific sales down 3.1%, will complicate the group's efforts to meet those aggressive benchmarks.

North American gains, too, will be difficult to maintain after the group took a €1.44 billion writedown earlier this year linked to ongoing "serious issues" at its digital agency, Razorfish, which it merged with SapientNitro in late 2016. It also lost big-name client such as Coca-Cola (KO) - Get Report , Wal-Mart Stores (WMT) - Get Report and Procter & Gamble (PG) - Get Report , all of which left the group's U.S. agencies over a six-month period spanning 2015 and 2016 amid changing campaign strategies and increasing pressure from data-driven advertizing tactics from Google and Facebook (FB) - Get Report

Publicis' weakness pulled down shares in WPP plc, its U.K. rival and the world's biggest advertizing group, with shares falling 2.34% to 1,375 pence each in London.

WPP shares were hammered in late August when it said it may see no revenue growth this year, after forecasting an advance of 2%, after one of it biggest clients, brands giant Unilever plc, slashed the number of agents it used amid a business realignment that followed an aborted takeover attempt from Kraft Heinz Co. KHC.

"That sent a shock-wave through the industry," WPP CEO Sir Martin Sorrell told Bloomberg at the time. "It obviously had an effect in terms of people spending, particularly in the packaged goods sector."