Private equity firm Warburg Pincus is in advanced talks to acquire Chennai-based medical equipment manufacturer Appasamy Associates, said people aware of the development. US-based Warburg has signed an exclusivity agreement with Appasamy and the due diligence has started, they said. The promoters of Appasamy are expecting a valuation of ₹4,000-4,500 crore, the people cited earlier said, adding that Warburg Pincus plans to acquire 65-70% stake in the company and have the current management run the company.