PARIS (Reuters) - Sanofi is betting on recent multibillion-dollar acquisitions and new drugs to drive "a new period of growth" from the second half of 2018 and offset persistent weakness in its key diabetes business.

The French pharmaceutical company on Friday reported sluggish first-quarter profit growth, blaming a stronger euro and lower sales from the diabetes unit, and hinted at another difficult quarter ahead.

Despite the slow start, Sanofi confirmed its 2018 outlook and announced a 1.5 billion euros (1.31 billion pounds) share buyback programme, a bid to reassure investors ahead of an annual shareholder meeting next week.

The message failed to impress, however, with the company's shares down 1.5 percent in morning trading.

"There is no significant research and development news," Barclays analysts wrote in a note. "There is also no underlying full-year guidance change, whilst forex is guided to be worse."

Chief executive Olivier Brandicourt is under pressure to deliver a turnaround and strong growth after restructuring Sanofi's business since taking over in 2015.

New acquisitions and products such as eczema drug Dupixent have been central to his strategy to diversify into new areas and counter competition from diabetes generics, in particular in the U.S. market.

"We anticipated certain challenges and we have made significant progress this quarter on strategic priorities," Brandicourt told reporters.

He said Sanofi was now better positioned to generate stronger growth.

Business net income was up 0.4 percent at constant exchange rates to 1.6 billion euros in the first quarter, as total sales fell 0.4 percent to 7.9 billion.

Analysts polled by Reuters in partnership with Inquiry Financial had forecast on average a net profit of 1.42 billion euros and net sales of 8 billion.

EURO STRENGTH BITES

Sanofi said a stronger euro had a negative effect of 8.3 percent on sales in the first quarter. Over the full year, the hit from currency swings is seen at around 7 percent on earnings per share compared with a previous estimate of 3-4 percent.

Diabetes and cardiovascular sales were down 15.7 percent - a new insulin missed estimates - but revenue at the speciality care Genzyme unit rose 16.2 percent.

Sanofi agreed in January to buy U.S haemophilia specialist Bioverativ for $11.6 billion and Belgium's Ablynx, which is developing an experimental drug for a rare blood disorder, for 3.9 billion euros.

It is also in exclusive talks with private equity firm Advent International to sell its Zentiva European generics drugs arm for 1.9 billion euros.

Following the integration of Bioverativ and Ablynx, Sanofi reported sales of 64 million euros in a new rare blood disorder franchise.

Sanofi is still grappling with a health scare surrounding its world-first dengue vaccine in the Philippines that shows no sign of abating. Separately, some investors have said the firm is still lacking a robust portfolio of new drugs.

Sanofi hopes its hiring of former Roche top scientist John Reed to head its research operations from July 1 will help soothe those concerns. He will replace departing industry veteran Elias Zerhouni when he retires.

Asked whether the group's dengue vaccine still had a future after the World Health Organization recommended Dengvaxia should only be used after testing, Brandicourt reiterated his confidence in the drug.

"Dengvaxia has a very important role in the future to play. What we have experienced may be something that will happen to other vaccines in development against dengue."

Japan's Takeda Pharmaceutical, the United States National Institute of Health and Brazil's Butantan Institute are developing rival products.

(Editing by Richard Lough and Mark Potter)

By Matthias Blamont