Sanofi boosts stake in Regeneron

French drugmaker Sanofi is buying more shares in US biotech company Regeneron Pharmaceuticals, its partner in the development of potential treatments for cholesterol and rheumatoid arthritis. Sanofi controls 16.7 per cent of Regeneron, or 15.82m shares. Sanofi said in an email that it has the right to raise the stake to as much as 30 per cent under its decade-long partnership with Regeneron.