* Dainippon to buy 10% stake in Roivant and interests in 5 units
* Schizophrenia treatment Latuda to lose US exclusivity in 2023
* Japan pharma firms grapple with declining population at home (Adds Dainippon CEO comment, context and stock price)
By Rocky Swift
TOKYO, Sept 6 (Reuters) - Japan's Sumitomo Dainippon Pharma Co will pay $3 billion for a 10% stake in Swiss drugmaker Roivant Sciences Ltd and interests in five of its biopharmaceutical businesses, the two companies said on Friday.
The deal, which will open up new drug lines for Sumitomo Dainippon, will also give it the option to acquire interests in an additional six businesses, as well as access to Roivant's technology platforms, they said in a statement.
It comes as Sumitomo Dainippon's schizophrenia treatment Latuda is due to lose its U.S. market exclusivity in 2023. The Japanese company will take ownership of Roivant units that develop treatments for prostate cancer, urinary diseases, pediatric illnesses and respiratory diseases, they said.
"We look forward to deepening our relationship with Roivant, which has a rich development pipeline, technology platforms, and distinctive talents," Sumitomo Dainippon CEO Hiroshi Nomura said in the statement.
Like its rivals, Japan's seventh-largest pharma company by revenue, is grappling with a declining population at home and a need to go abroad to find growth.
While the bulk of Japanese drug firms have been largely cautious about overseas acquisitions, there are signs of change. Takeda Pharmaceutical this year completed a $59 billion purchase of Shire Plc, catapulting it into the list of the world's top 10 drugmakers by sales - a rarity for a Japanese pharma company.
A fifth Roivant business unit will also be transferred before the deal's conclusion, the two companies said.
The 11 businesses include more than 25 clinical programs with multiple product launches expected between 2020 and 2022, they said.
Shares of Sumitomo Dainippon finished up 1.7% at 1,800 yen on Friday. (Reporting by Rocky Swift; Editing by David Dolan and Muralikumar Anantharaman)