Brookfield Asset Management Ltd. is preparing to walk away from a plan to acquire Grifols SA over disagreements on valuation for the Spanish drug maker, according to people familiar with the matter.

Grifols' American depositary receipts slumped following a report that Brookfield Asset Management plans to abandon its acquisition of the Spanish pharmaceuticals company. The stock was down 18% at $7.14 in premarket trading. Shares had already fallen nearly 25% year-to-date when the market closed Tuesday.

Brookfield Asset Management has walked away from an acquisition of Spanish healthcare group Grifols after months of negotiations, sending shares in the short seller target down almost 13 per cent.