Dublin-based pharmaceutical company Allergan has U-turned on its interest in buying Shire.
Earlier on Thursday, a bidding war erupted as Shire rejected a £43bn offer from Japanese competitor Takeda, before Allergan confirmed its own interest in buying the business.
The offer was the third from Takeda that had been turned down by the firm.
But a statement released on Thursday evening confirmed that the company had backtracked on its interest for shire.
Reuters quoted sources who were familiar with the matter, who explained that investors were allegedly concerned about Allergan overstretching its resources.
When Allergan originally said it was considering making an offer, it explained that its interest in Shire was part of the company "evaluating a full range of potential strategic actions" to create value for shareholders.
It also confirmed that it was required by UK takeover law to make an offer or withdraw its interest by 17 May.
Allergan is known for making botox along with a range of other medicines.