The drug candidate that can enhance the effect of chemotherapy
Isofol develops the drug candidate arfolitixorin, designed to enhance the efficacy of todays and future cancer treatments. The goal is to help more patients gain better conditions to respond to their treatment and hence achieve an improved prognosis.
Arfolitixorin has the potential to become a key component of today’s standard treatment for several forms of solid tumors. The drug candidate is now being investigated in a clinical phase Ib/II-study in patients with metastatic colorectal cancer. Currently, 5-FU-based chemotherapy is given as standard first-line treatment usually together with folate therapies to enhance its effect in several aggressive cancers. These folate drugs are broken down in the body and converted into the active metabolite [6R]-MTHF, which increases the tumor-killing effect of 5-FU while reducing the production of one of the building blocks that tumor cells need to multiply. While existing folate therapies require multi-step metabolic conversion, arfolitixorin consists of the active metabolite in its pure form. Arfolitixorin, therefore, has the potential to both enable improved efficacy and allow more patients to benefit from the treatment.
Solid evidence Platform
In recent years, Isofol has conducted several early phase clinical studies to investigate the efficacy and safety profile of arfolitixorin. The large data package generated so far, which constitutes a strong evidence platform shows that the drug is safe, well-tolerated and effective. Previous clinical studies have shown statistically significant results demonstrating that patients with colorectal cancer treated with arfolitixorin achieved three to four times higher concentrations of the active metabolite in tumor tissue compared with current folate therapies. When arfolitixorin was given together with 5-FU in the treatment of colorectal cancer, the tumor-killing effect was enhanced, resulting in increased cancer cell death.
Ongoing clinical phase Ib/II study
To demonstrate the clinical potential of arfolitixorin, Isofol is conducting a phase Ib/II clinical study to determine the optimal dosing regimen for safety, tolerability and efficacy. The study design was approved by the German Medicines Agency in March 2025. Recruitment of treatment-naive patients with metastatic colorectal cancer started in April 2025 at the leading academic hospital Charité – Universitätsmedizin Berlin.
The goal is to expand the study in phase II to include both additional study centers in Europe and patients in Japan in 2026 in collaboration with Isofol’s partner, Solasia Pharma K.K. In parallel, discussions are ongoing with the U.S. Food and Drug Administration (FDA).
Interview with Charité – Universitätsmedizin Berlin
Watch the interview with Prof. Sebastian Stintzing who is the principal coordinating investigator in Isofol’s on-going phase Ib/II study.
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