US-based investment firm Apollo Global Management has agreed to acquire an additional 18% stake in health insurer Athene in a transaction worth around $1.55bn.

As per the terms of the deal structured as a stock swap, Apollo will acquire nearly 35.5 million common shares of Athene for $350m cash and also give a 7% stake in its holding company.

Upon completion of the transaction, Apollo shareholding in Athene will increase to 35% from existing 17%.

Athene chairman and CEO Jim Belardi said: “After carefully reviewing Athene’s options to unlock value for shareholders, Athene and Apollo determined it is prudent to eliminate Athene’s multi-class share structure and make other enhancements to the companies’ mutually beneficial relationship.

“This transaction will remove a material impediment to additional index inclusion and strengthen our corporate governance profile by aligning voting rights with the economic interests of all shareholders.

“We believe the combination of these factors will greatly enhance Athene’s appeal to a much broader group of active and passive investors.”

Apollo chairman and CEO Leon Black said: “Athene and Apollo have developed a special and symbiotic relationship since Athene’s inception a decade ago.

“By nearly doubling our economic interest in Athene to approximately 35%, we are reinforcing the durability of our relationship, and enhancing the strong alignment between the two companies.”

Apollo will gain five seats to Athene’s 15 members’ board based on expected ownership following the completion of the transaction.

In February this year, Apollo Global Management wrapped up the previously announced acquisition of Bermudian insurer Aspen for $2.6bn.