Ivermectin converts cold tumors hot and synergizes with immune checkpoint blockade for treatment of breast cancer (with 2026 expression of concern)
The mouse study behind the current trials: ivermectin on its own did nothing to breast tumours in mice, but with an anti-PD-1 antibody the pair shrank them. The journal has since flagged duplicated images in one figure and the raw data are gone.
Overview
In mouse models of breast cancer, ivermectin induced immunogenic cell death and T-cell infiltration, and as a modulator of the ATP/P2X4/P2X7 axis reduced regulatory T cells and suppressive myeloid cells; neither ivermectin nor the anti-PD-1 antibody alone showed efficacy in vivo, but the combination limited tumour growth, produced complete responses and reduced relapse in neoadjuvant, adjuvant and metastatic settings (Draganov mouse study 2021). In June 2026 the journal issued an editorial expression of concern: multiple highly similar images were found between panels 4d and 4f, an author correction had already removed some duplicates, further checks found more, and the authors stated that the original data are no longer available, so readers are advised to interpret these data with caution (Expression of concern 2026).
- Mice only: ivermectin alone had no effect on tumour growth; ivermectin plus anti-PD-1 limited growth and produced complete responses.
- Expression of concern, 5 June 2026: duplicated images in Figure 4d and 4f, original data unavailable.
This is the scientific basis for pairing ivermectin with checkpoint antibodies in the Cedars-Sinai and ICONIC trials. Its key figure is now in doubt, which makes those trials more important, not less, as the only way to find out whether the effect is real.
- Animal study; no patient data.
- Editorial expression of concern issued 5 June 2026 over duplicated images; original data no longer available.
- An author correction (npj Breast Cancer 2026;12:31) preceded the expression of concern.
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