Teva Pharmaceutical, the Israeli drugmaker, is nearing a deal to acquire Allergan's generics drug unit for between $40 billion and $45 billion, according to people familiar with the matter.

A deal, which one person said could be announced within days, would be the latest blockbuster agreement in the pharma sector.

Until recently, Teva had been entirely focused on its attempt to acquire rival generic drugmaker Mylan. Earlier this month, Teva was preparing to increase its offer to buy Mylan to $43 billion in what would have been the latest move in a fiercely contested hostile takeover campaign, people familiar with the matter previously said.

If a deal is clinched with Allergan it is unlikely to pursue Mylan any further, said one person familiar with the firm's thinking.

Teva has built a 4.6 per cent share of Mylan over the past months. But this week an independent foundation, under the terms of Mylan’s recently acquired Dutch domicile, activated a sort of poison pill that gave it 50 per cent of the voting rights in the company. The foundation, known as a stichting, said it had determined a Teva-Mylan deal was not in the best interests of shareholders. – Copyright The Financial Times Limited 2015