BridgeBio licensed the exclusive Japanese rights to develop and sell an experimental dwarfism drug to Tokyo-based pharma firm Kyowa Kirin, firms said earlier this week.

Terms of the deal call for BridgeBio to receive $100 million in cash upfront, as well as milestone payments and royalties up to the high-twenties percent on sales of the drug, infigratinib.

The collaboration with Kirin “will ensure the development of infigratinib for children living with achondroplasia, and eventually for other skeletal dysplasias in Japan,” said BridgeBio CEO Neil Kumar.

The deal comes at a pivotal time for BridgeBio. 

The upfront payment, along with a recently secured financing of up to $1.25 billion in capital, beef up BridgeBio’s balance sheet as the company gears up for the anticipated launch of ATTR-CM drug acoramidas, whose approval is expected in the second half of the year. 

Achondroplasia, a rare form of dwarfism or short stature, affects about 55,000 people in the U.S. and E.U., and 6,000 in Japan. It’s caused by an activating mutation in FGFR3 and an oral small molecule, infigratinib, is designed to inhibit FGFR3.

BridgeBio’s Phase 3 PROPEL trial, which is assessing infigratinib in children with achondroplasia ages 3 to 18, dosed its first patient in December. A Phase 2 trial demonstrated a 3.38 centimeter per year increase in annualized height velocity, which the company said was the “strongest clinical result published to date.”

Kyowa Kirin will kick off discussions with Japan’s regulator, the Pharmaceuticals and Medical Devices Agency (PMDA), this year for the go-ahead to begin a registrational trial in the country in 2025.

“It is important for us to strengthen our portfolio by introducing pipelines in the fields of bone and mineral disorders, including achondroplasia,” stated Yasuo Fujii, who is chief strategy officer, managing executive officer and VP/head of Kyowa Kirin’s strategy division. 

Based on the trial results, infigratinib has “high potential” for treating achondroplasia, added Fuji. “We will steadily advance the development in Japan and aim to deliver life-changing value to people with skeletal dysplasias including achondroplasia.”

Infigratinib is being developed to treat other FGFR3-driven skeletal dysplasias, as well. Clinical development in a related disease, hypochondroplasia, is set to start in the first half of the year following the release of positive preclinical data.

This isn’t Kyowa Kirin’s first licensing deal involving a rare-disease drug. For the last decade or so, the Japanese pharma has licensed North American marketing rights for its home-grown drug Crysvita (burosumab) to Ultragenyx Pharma. 

Recently, though, the firms said Kyowa will assume commercial leadership in the U.S. and Canada for Crysvita, which is approved in those markets for both X-linked hypophosphatemia (XLH), a rare inherited disorder that affects the bones and teeth, as well as for FGF23-related hypophosphatemia in tumor induced osteomalacia (TIO).