“If arfolitixorin surpassing the efficacy of leucovorin, it could represent a breakthrough”

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Yoshihiro Arai is President and CEO of the specialty pharma company Solasia Pharma, Isofol’s partner in Japan for developing the drug candidate arfolitixorin. Under a 2020 license agreement, Solasia holds exclusive rights to arfolitixorin in Japan and joined Isofol’s phase III AGENT study. In recent years, Yoshihiro Arai has led this collaboration, reflecting Solasia’s long‑term commitment to the clinical development of arfolitixorin and to the inclusion of Japanese patients in upcoming trials.

During 2025, Solasia became a shareholder in Isofol. How does Solasia’s ownership in Isofol strengthen the long-term collaboration?
— Solasia and Isofol have been partners in conducting international joint clinical trials for the development of arfolitixorin, building a strong partnership in drug development. By becoming a shareholder in Isofol, we anticipate closer collaboration on the development of arfolitixorin and expect this to serve as a milestone for further business expansion by both companies.

What lessons has Solasia learned from the AGENT study that can support the continued development of arfolitixorin?
— We learned many things from the AGENT trial. While the scientific potential of arfolitixorin was fully recognized, we observed differences in how clinical trials are approached between countries. Specifically, although the exact reason is not entirely clear, it was found that the reduction in the core drug 5-FU was greater in Japan compared to other countries, which impacted the overall results. This highlighted the need to more clearly define the trial and treatment in future clinical trials.

Regarding trial management, in the AGENT trial, Isofol conducted trial operations in Japan through a local CRO with Isofol as a sponsor. Solasia was not the local sponsor and could not directly participate in discussions with Isofol about trial content or trial management. When transitioning from development to marketing, involvement from the development stage is invaluable. In the next clinical trial, Solasia will be able to participate directly in trial planning alongside Isofol as the local sponsor.

Could you describe how the Japanese study will be conducted?
— In the phase Ib/II study already underway in Germany, Japan is strategically integrated into the global development program. Tactically, the leading proposal is for Japan to participate as a separate cohort starting from the phase II part of the ongoing phase Ib/II study. The results obtained here will be analyzed both for the overall trial and specifically for the Japanese cohort, providing valuable information for planning the pivotal study required for regulatory approval. In any case, the pivotal study is expected to be conducted as a global clinical trial including Japanese patients, enabling simultaneous regulatory submissions in Japan, the US, and Europe.

How do you view arfolitixorin’s potential to improve prognosis for patients with colorectal cancer?
— In the AGENT trial, unfortunately, superiority over the standard drug leucovorin could not be demonstrated. However, based on detailed analysis of the results, new preclinical data, and the mechanism of action, we believe arfolitixorin has a high potential to demonstrate superior treatment outcomes compared to leucovorin in the first-line treatment of colorectal cancer. It can also be expected to improve patient prognosis.

What commercial prospects do you see for arfolitixorin in the Japanese market, the second-largest addressable market after the US?
— Currently, multi-agent combination therapy, including 5-FU, remains the primary treatment for colorectal, gastric, and pancreatic cancers. It has maintained this position for a long time, and we believe it will continue to do so. However, this also means that no new combination therapy drugs have emerged for a long period. In this environment, if arfolitixorin demonstrates results surpassing the efficacy of leucovorin, the current standard drug, it could represent a breakthrough. Leucovorin in multi-agent combination therapy containing 5-FU could be replaced by arfolitixorin, and we see substantial market potential.