# A phase 2a clinical study on the safety and efficacy of individualized dosed mebendazole in patients with advanced gastrointestinal cancer

Source: https://onco.cc/key-papers/paper-mansoori-mebendazole-gi-cancer-phase-2a-sci-rep-2021/  
OnCo record `paper-mansoori-mebendazole-gi-cancer-phase-2a-sci-rep-2021` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A Swedish trial gave mebendazole to ten people with advanced bowel and stomach cancers that had stopped responding to treatment; it was safe, but every patient's cancer kept growing, four of them unusually fast.

## Summary

Patients with treatment-refractory gastrointestinal cancer received mebendazole at individually adjusted doses up to 4 g a day aiming at a serum level of 300 ng/mL; 11 were included and 10 started treatment (Mebendazole phase 2a 2021). Two stopped before and the remaining eight after the eight-week CT scan, all for progressive disease, four met suggested criteria for hyperprogression, only five reached the target level, and no severe adverse effects were observed; the authors conclude that new approaches such as prodrugs or combinations would be needed for further exploration (Mebendazole phase 2a 2021).

## Fields

- Kind: Key paper
- Last checked: 2026-09-24
- Journal: Scientific Reports
- Year: 2021
- DOI: 10.1038/s41598-021-88433-y
- Authors: Mansoori S, Fryknäs M, Alvfors C, Loskog A, Larsson R, Nygren P.
- Findings: 10 treated; all 10 stopped for progressive disease by the eight-week scan; four met hyperprogression criteria.; No severe adverse effects; only five reached the target serum concentration.
- What it means: The only completed efficacy study of an internet-famous dewormer in cancer patients found no benefit in anyone. It is the clearest human result in this whole story.
- Caveats: Small single-arm study in heavily pretreated patients; drug exposure was below target in half of them.

## Sources

- Mebendazole phase 2a 2021: https://doi.org/10.1038/s41598-021-88433-y
- PubMed: https://pubmed.ncbi.nlm.nih.gov/33903692/

## Connected records

- cancers: [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Gastric & gastro-oesophageal junction cancer](https://onco.cc/cancers/gastric/)
- technologies: [Systematic drug repurposing](https://onco.cc/technologies/drug-repurposing/)
- drugs: [Mebendazole](https://onco.cc/drugs/mebendazole/)
- terms: [Single-arm trial](https://onco.cc/terms/single-arm/)

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