Research on arfolitixorin consolidated into a solid evidence platform

The drug candidate arfolitixorin is the first and only direct-acting form of folate that requires no conversion in the body. Preclinical studies have demonstrated that arfolitixorin can achieve higher concentrations in tumor tissue than existing folate-based drugs, and accumulated clinical data suggest that arfolitixorin has potential as a future cancer treatment with good efficacy and safety profiles.

In recent years, Isofol has conducted several early phase clinical studies to investigate the efficacy and safety profile of arfolitixorin. The results indicate that the drug is safe, well tolerated and effective.

Phase III study shows efficacy

In 2022, the AGENT study, which was designed as a pivotal phase III trial, was terminated. The study was an open-label, multicenter, randomized controlled trial of 490 patients in North America, Europe, Asia and Australia comparing arfolitixorin to the current standard folate drug leucovorin, both of them in combination with 5-FU and other drugs included in the standard first-line treatment for patients with metastatic colorectal cancer. The primary endpoint of the study, to show that arfolitixorin is superior to leucovorin as measured by the Overall Response Rate (ORR), was not met as arfolitixorin showed numerically comparable, but not better, efficacy than leucovorin.

Since then, extensive analyses and preclinical studies have been conducted to determine the circumstances that may explain the failure to meet the primary endpoint. A post hoc, per-protocol analysis of AGENT showed that compliance with the study protocol was low in some respects, and that arfolitixorin showed significantly better results when the analysis was restricted to patients treated according to protocol with respect to drug administration. In all regions excluding Japan, arfolitixorin was statistically significantly better than leucovorin and in North America, the difference in favor of arfolitixorin was even more pronounced. The analyses also indicate that the dose and administration regimen used in the AGENT study was suboptimal and that a higher dose given earlier may provide better efficacy.  

Preclinical studies show an enhanced effect with higher dose

Additional analyses conducted in 2024-2025 have used various approaches and methods to demonstrate that the dose and administration regimen used in the AGENT study was suboptimal, and that alternative dosing regimens have the potential to provide better efficacy. Two preclinical studies have demonstrated a clear dose-response relationship for arfolitixorin – meaning efficacy increases with dose – unique to arfolitixorin and is not observed with leucovorin, the current standard of care. Consequently, higher doses of arfolitixorin are used in the ongoing study. The preclinical studies have also made comparisons of arfolitixorin and leucovorin and found that arfolitixorin demonstrates better efficacy. This appears to hold across multiple drug combinations.

Timing of administration is key

In addition to this, analyses have demonstrated the importance of administering arfolitixorin and other folates at the optimal time to ensure concentrations of the active substance is at it’s highest when needed. It is pharmacologically essential that the concentration of the active substance is high in the tumor tissue before the biochemical reaction with 5-FU begins. For this reason, folate is administered prior to 5-FU in clinical practice worldwide – a protocol that was not followed in the AGENT study, where arfolitixorin was given 30 minutes after 5-FU. In contrast, leucovorin was administered before 5-FU in the study’s control arm. This has been corrected in the new study programme.

The evidence platform in short

Unlike other early-stage clinical development programs, arfolitixorin is supported by an extensive data package based on preclinical and clinical studies conducted. The key findings from these studies are as follows:

• Dose-response relationships demonstrated in previous preclinical studies indicate that higher doses may yield improved efficacy. Furthermore, optimizing the timing of administration should further enhance efficacy due to synergistic effects between arfolitixorin and 5-FU.
• Higher doses may potentially be administered without compromising the safety profile, as indicated by PK simulations and safety data from prior studies.
• In a comprehensive global phase III study, arfolitixorin demonstrated efficacy comparable to that of the control group.

Based on these studies and analyses, a new study program is now being implemented to evaluate new dose regimens with ensured protocol compliance. The design of the new program is based on the large data package generated so far, which constitutes a strong evidence platform that strengthens Isofol’s confidence in being able to show positive results.