Rakuten Medical has added to its tally of megarounds, pocketing another $100 million to push its lead light-based cancer therapy toward a targeted FDA approval filing in 2028.
San Diego-based Rakuten, which takes its name from a Japanese tech conglomerate that has bankrolled its progress, is built on a photoimmunotherapy platform. The biotech conjugates cell-targeting moieties such as antibodies to light-activatable dyes. Like antibody-drug conjugates, Rakuten’s assets selectively deliver a payload to target cells. The key difference is that the payload is inactive when administered.
Physicians activate the payloads using a medical device that shines light on the target cells. If Rakuten is right, payload activation will compromise the membranes of the target cells, directly shrinking the tumor and potentially triggering an anticancer immune response.
Rakuten is putting the idea to the test in a global phase 3 trial evaluating ASP-1929 in combination with Merck & Co.’s Keytruda as a first-line treatment for recurrent head and neck cancer. Patients in the control cohorts are receiving Keytruda as a monotherapy or in combination with chemotherapy.
Having initiated the trial in 2024, Rakuten aims to have the data to support an FDA approval filing in 2028. TaiAx Life Science Fund, a joint venture between Taiwanese and Japanese companies, is backing Rakuten’s plan. The fund led the $100 million series F round, with participation from multiple Japanese financial institutions, Taiwanese venture firms and existing investors, including the Rakuten Group and its CEO.
The Rakuten Group and its CEO, Mickey Mikitani, have supported the biotech through a series of rounds. In 2018, the company, then called Rakuten Aspyrian, raised $150 million in a series C round. The following year, the Rakuten Group drove a $100 million series C-1 round. The biotech raised a $166 million series D round in 2021 and followed up with a $119 million series E financing in 2024.
Founded in 2010, the biotech is now closing in on data that will determine whether it can turn the heavy investor support into an FDA-approved product. The upcoming phase 3 readout will be a key moment for ASP-1929 and Rakuten’s broader platform, given the novelty of the photoimmunotherapy approach and the overlaps between the designs of the biotech’s candidates.
ASP-1929 consists of the anti-epidermal growth factor receptor (EGFR) antibody cetuximab conjugated to the light-activatable dye IRDye 700DX. The widespread overexpression of EGFR in head and neck cancer has shaped Rakuten’s strategy for ASP-1929. Beyond the lead program, Rakuten has candidates that feature the dye used in ASP-1929 conjugated to antibodies against CD25 and PD-L1.
The CD25 candidate is in a phase 1 trial in Japan. Rakuten is preparing to take the PD-L1 program into a phase 1 trial. Rakuten’s ability to validate ASP-1929 in the phase 3 trial could shape interest in the platform, both from investors that have funded the biotech to date and from biopharma companies.