Sigma Healthcare’s biggest shareholder will seek support for board changes over the company’s decision to wage a bidding war for Priceline owner Australian Pharmaceutical Industries, just two years after dismissing an offer from the target that he says would have been better for shareholders.

Sigma lobbed an indicative non-binding cash and scrip deal valuing rival drug wholesaler at $773.5 million on Monday, topping Wesfarmers’ all-cash bid and winning access to API’s books and a favourable reaction from its board.