French drug maker Sanofi-Aventis is reportedly expected to sweeten its bid for U.S. biotechnology company Genzyme later this week. The two companies are said to be negotiating a cash deal worth $74 a share or $19 billion, plus extra payments linked to experimental multiple sclerosis drug Lemtrada. A Wall Street Journal report said the talks have taken longer than anticipated as Sanofi continues to examine the books of Genzyme. Sanofi is said to be concerned about the past manufacturing problems at Genzyme. Genzyme had last year rejected Sanofi's $69 per share or $18.5 billion offer on grounds of undervaluation. Sanofi took the bid directly to shareholders in October and extended the offer until February 15. The purchase of Genzyme would give Sanofi access to the growing market of rare diseases and also compensate for revenue losses as patents expire on some of its biggest-selling products.