“There is a broad interest in optimizing 5-FU-based chemotherapy”

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Sebastian Stintzing heads the department at Charité – Universitätsmedizin Berlin responsible for an extensive gastrointestinal cancer treatment program, with a particular focus on optimizing the treatment of colorectal cancer. Charité is the primary study center for Isofol’s phase Ib/II study of arfolitixorin, for which Sebastian Stintzing serves as the principal coordinating investigator. In an interview he answered three questions about the current state of research in the field.

What role do you see arfolitixorin playing in the treatment landscape, particularly in metastatic colorectal cancer?
— The base of treatment in colorectal cancer is 5-FU-based chemotherapy. What has been interesting, looking at developments over recent years – with increasingly more precision oncology options, as witnessed at the scientific conference ESMO 2025 – is that these precision oncology and immuno-oncology agents are being combined with traditional backbone chemotherapy. By doing this, we are seeing remarkable results – and clearly, backbone chemotherapy is here to stay.

If we are able to optimize this kind of backbone chemotherapy by adding arfolitixorin instead of leucovorin to 5-FU-based chemotherapy, that would be a significant step forward for our patients and toward a more efficacious treatment of these cancers.

Do you also see this opportunity in other types apart from colorectal cancer?
— Absolutely. Gastrointestinal cancers account for around 25% of all cancer cases, and I would say that approximately 95% of those are treated with 5-FU, in both neoadjuvant and metastatic disease. So there is significant potential here. And outside of the gastrointestinal area, 5-FU-based chemotherapy is also used – for example, in lung cancer and breast cancer. There is therefore a broad interest in optimizing 5-FU-based chemotherapy.

You are heading the ongoing phase Ib trial. What can you tell us about it without revealing too much of the data?
— We are treating patients with metastatic colorectal cancer within this trial, and we are currently still in the dose-optimization phase. When we made an interim reading the patients who had been treated so far at the end of February 2026, we saw no dose-limiting side effects. Preliminary results also showed that all patients included in the study had responded to the treatment and showed tumor shrinkage that corresponded to up to a halving of the total tumor size. Half of the patients had also responded so well to the treatment that they were removed from the study for consideration of tumor surgery, the tumor was surgically removed – which is unexpectedly positive in this patient group since this patient population is particularly difficult to treat.