# Ivermectin converts cold tumors hot and synergizes with immune checkpoint blockade for treatment of breast cancer (with 2026 expression of concern)

Source: https://onco.cc/key-papers/paper-draganov-ivermectin-cold-tumours-npj-breast-cancer-2021/  
OnCo record `paper-draganov-ivermectin-cold-tumours-npj-breast-cancer-2021` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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.

## Summary

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).

## Fields

- Kind: Key paper
- Last checked: 2026-09-24
- Journal: npj Breast Cancer
- Year: 2021
- DOI: 10.1038/s41523-021-00229-5
- Authors: Draganov D, Han Z, Rana A, Bennett N, Irvine DJ, Lee PP.
- Findings: 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.
- What it means: 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.
- Caveats: 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.

## Sources

- Draganov mouse study 2021: https://doi.org/10.1038/s41523-021-00229-5
- Expression of concern 2026: https://doi.org/10.1038/s41523-026-00988-z
- PubMed: https://pubmed.ncbi.nlm.nih.gov/33654071/
- Expression of concern on PubMed: https://pubmed.ncbi.nlm.nih.gov/42248882/

## Connected records

- cancers: [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- technologies: [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/)
- drugs: [Ivermectin](https://onco.cc/drugs/ivermectin/)
- terms: [In vitro and in vivo](https://onco.cc/terms/in-vitro-in-vivo/), [Preclinical](https://onco.cc/terms/preclinical/)
- trials: [ICONIC: ivermectin combined with immune checkpoint inhibition in cancer (University of Florida phase 2)](https://onco.cc/trials/nct07487805/), [Ivermectin with balstilimab or pembrolizumab in metastatic triple-negative breast cancer (Cedars-Sinai phase 1/2)](https://onco.cc/trials/nct05318469/)

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