SoftBank Group Corp. is backing away from part of its planned bailout of WeWork, people familiar with the matter said, privately citing several regulatory investigations of the office-sharing company.

A notice sent to WeWork shareholders Tuesday said that SoftBank believes regulatory probes into the startup’s business, including from the Securities and Exchange Commission and Justice Department, give it an out under the deal struck last fall to purchase $3 billion of WeWork shares from existing investors.

...