Teva Pharmaceutical Industries (TEVA.TA) has agreed to buy Allergan Plc’s (AGN.N) generic drugs business for $40.5 billion in a deal that will turn Teva into one of the top 10 pharmaceutical companies. The acquisition should help Israel-based Teva, already the world’s largest generic drugmaker, boost growth at a time its top drug, multiple sclerosis treatment Coxaprone, is facing competition.