May 3 (Reuters) - Roivant Sciences has agreed to go public through a merger with a blank-check firm backed by former KKR & Co Inc dealmaker Jim Momtazee, in a deal that values the Swiss biotech company at $7.3 billion.

The deal with Montes Archimedes Acquisition Corp, a special purpose acquisition company (SPAC), is expected to deliver up to $611 million of gross proceeds to fund discovery and development programs, the companies said on Monday.

That includes up to $411 million currently held in the SPAC's trust account and $200 million from new and existing investors including Fidelity Management and SoftBank Group Corp unit SB Management.

Shares of Montes Archimedes Acquisition were up 3.5% at $10.2 before the bell.

Montes Archimedes went public in a $400 million initial public offering (IPO) in October last year and is sponsored by Patient Square Capital Patient, which was launched by Momtazee to pursue private equity deals in the healthcare sector.

SPACs are shell companies that raise funds through an IPO to take a private company public through a merger at a later date.

Founded in 2014, Roivant has multiple subsidiaries focused on developing treatments for multiple cancers, nervous system and immune system disorders, including Immovovant Inc and Sio Gene Therapies Inc.

In February, the company said it would buy drug developer Silicon Therapeutics for $450 million to strengthen its artificial intelligence capabilities for drug discovery.

Following its acquisition, Roivant will continue to be led by Chief Executive Officer Matthew Gline, while founder Vivek Ramaswamy will remain executive chairman.

The biotech firm said it expects the deal to close in the third quarter of this year, after which it plans to list on the Nasdaq under the ticker symbol "ROIV". (Reporting by Niket Nishant and Dania Nadeem in Bengaluru; Editing by Ramakrishnan M.)