San Diego biotech Aspyrian Therapeutics has raised $40 million to pursue a new way to fight cancer.

The funding comes from Japanese billionaire Hiroshi Mikitani, according to an Aspyrian statement. Mikitani is the owner of Japan’s largest online retailer, Rakuten. He led the round with his private companies.

The local biotech said it was cleared by the FDA to start clinical studies of its potential head-and-neck cancer treatment, which uses near-infrared light to activate a tumor-killing toxin. The treatment is called photoimmunotherapy, and it was invented at the National Cancer Institute by researcher Hisataka Kobayashi. This form of precision therapy uses lasers to activate monoclonal antibodies that, in turn, stimulate immune cells to attack cancer cells in a localized area. It’s meant to keep damage to healthy cells at a minimum.

“Photoimmunotherapy has the potential to transform the standard of care of a number of cancer areas,” said Miguel Garcia-Guzman, president and CEO of Aspyrian Therapeutics, in a statement. “We are honored to have the support from Hiroshi Mikitani and share a common vision to provide cancer patients with novel targeted approaches to battle and conquer their disease.”

Aspyrian is recruiting patients for a Phase 1 study of its lead asset, RM-1929, and is exploring the use of photoimmunotherapy in other cancers as well.