Ok, If Sanofi is a public company they will have to declare to the stock holders why they spent almost a half a billion dollars on the rights to this treatment! That being said, there could be two possible reason why they paid so much for it. First, if this is a threat to their current product they would buy it to prevent a competition destroying their diabetic market. Second, if the patent for Lantus is close to expiring they maybe looking for a future product to replace Lantus once it goes into the generic market. If Lantus goes generic the price for it will drop significantly. The best way to find out more is to keep looking the their SEC filings because they would need to account for that large of an expenditure!