The world’s largest drug manufacturer Pfizer Inc. has held informal discussions regarding a planned acquisition of AstraZeneca Plc. However, the informal talk had turn sour and has been discontinued, said two sources that were familiar with the matter.

The sources who spoke in condition of anonymity said that the two companies have halted negotiations. One of the sources said that the talks occurred several months ago and no plans to resume were seen. The plan to acquire AstraZeneca was first reported on London’s Sunday Times. The paper said that Pfizer has approached AstraZeneca in a deal valued $101 billion.

If the plan was resumed, the acquisition would become among the biggest in the pharmaceutical industry. A deal to acquire AstraZeneca would enable Pfizer to develop early-stage drugs for cancer treatment.

In an email, Pfizer spokesperson Andrew Topen said, “We don’t comment on market speculation or rumors.” Meanwhile, Pfizer representative Esra Erkal-Paler refused to comment regarding the report.