March 27 (Reuters) - Moderna said on Wednesday it has entered into an agreement with private equity firm Blackstone's life science investment platform for a funding of $750 million to develop its mRNA flu vaccines.

Blackstone Life Sciences will get commercial milestone payments and low-single digit royalties as part of the agreement, the COVID-19 vaccine maker said.

The funding is expected to support the biotech firm that has been working on multiple vaccines to make up for the decline in sales of its COVID shots sold under brand name Spikevax.

Moderna has plans to spend about $4.5 billion in 2024 towards research and development.

(Reporting by Leroy Leo and Sneha S.K. in Bengaluru; Editing by Shinjini Ganguli)