Easter weekend has seen the rumour mill go into overdrive with reports that drug giant Pfizer has made advances on Anglo-Swedish drugmaker AstraZeneca.

UK paper The Sunday Times said Pfizer recently made an informal move on its London-based rival, offering around $101 billion to take the firm under its wing.

However, according to its unnamed sources, from both the banking and pharma sectors, the move was spurned by AZ and talks have now stalled.

AZ is said to be keen to redistribute a $70-billion pile of foreign cash rather than bring it back into the US and face a giant tax bill, the paper notes, and AZ could be an attractive proposition because of its respectable rack of drug candidates - particularly those in the cancer immunology field - in the pipeline. 

On the other side of the coin, AZ' sales are slipping and could "deteriorate massively by 2020 as several products go off patent", ISI Group analyst Mark Schoenebaum reportedly said in a client note.

Should Pfizer continue to pursue AZ it could ultimately lead to the largest mega-merger even seen in the industry, overshooting Pfizer's acquisition of Warner-Lambert in 2000, which, Bloomberg has calculated, is top of the list to date.

Both companies have thus far declined to comment.