New Delhi, Aug. 3 -- British pharmaceutical major AstraZeneca is exploring a possible merger with US-based Bristol Myers Squibb, which could create a combined company valued at nearly $400 billion, according to a Financial Times report published on Sunday.

While there is no certainty that the discussions will result in a formal agreement, the FT report said the two drugmakers have been holding merger talks for several months, citing people familiar with the matter.

If completed, the proposed transaction would rank among the largest corporate mergers ever undertaken.

The development comes less than a year after AstraZeneca announced plans to pursue a direct listing in the United States, seeking to benefit from higher market valuations w...