Which clinical trials have tested ivermectin as an anticancer therapy and what were their primary outcomes?
This fact-check may be outdated. Consider refreshing it to get the most current information.
Executive summary
Clinical testing of ivermectin as a cancer therapy is very limited and largely early-phase: the clearest ongoing human study is a phase I/II trial combining ivermectin with the PD‑1 agent balstilimab (NCT05318469), reported as safe and “encouraging” for clinical benefit rate in an ASCO 2025 abstract [1] [2]. Most other evidence remains preclinical—cell lines and animal studies showing antiproliferative and synergistic effects (e.g., pancreatic and breast cancer models) but no large randomized trials demonstrating tumor shrinkage or survival benefit [3] [4] [5].
1. What clinical trials exist — very small, mostly early‑phase testing
Human clinical work on ivermectin in oncology is scarce. The principal trial identified is a phase I/II investigator‑initiated study testing oral ivermectin combined with balstilimab (and in some descriptions pembrolizumab as an alternative arm) in metastatic triple‑negative breast cancer (TNBC), registered as NCT05318469 and summarized by Gateway for Cancer Research and an ASCO 2025 abstract [2] [1]. Other literature and systematic reviews note the clinical‑trial literature is minimal or “no reports” historically until these first investigator trials emerged, emphasizing that most published work is preclinical [4] [5].
2. Primary outcomes reported so far — safety signal and “encouraging” activity, not definitive efficacy
The ASCO 2025 abstract for the phase I/II TNBC study reports that the ivermectin + balstilimab combination was “safe and well tolerated” and showed an “encouraging clinical benefit rate (CBR)” in a heavily pretreated population, prompting continued study [1]. Gateway for Cancer Research frames the trial primarily as a Phase I safety evaluation with efficacy as a secondary endpoint [2]. No large randomized or phase III data showing improved progression‑free or overall survival have been published in these sources [1] [4].
3. What the preclinical data say — plausible mechanisms, many positive lab models
Laboratory and animal research repeatedly show ivermectin can inhibit proliferation, induce apoptosis, modulate signaling pathways (Wnt/β‑catenin, Akt/mTOR), sensitize cells to other agents, and synergize with other treatments (examples: ivermectin + recombinant methioninase eradicated MiaPaCa‑2 pancreatic cells in vitro; ivermectin enhanced paclitaxel efficacy in NSCLC cell lines) [3] [6] [7]. Reviews emphasize abundant preclinical signals but caution these do not substitute for clinical evidence [8] [5].
4. Conflicting views and caveats — hype, repurposing appeal, safety uncertainties at oncologic doses
Advocates for repurposing stress ivermectin’s low cost and multiple proposed anticancer mechanisms; critics and reviews warn that most studies are in vitro or in mice and that pharmacokinetics, required dosing, and safety at anticancer exposures are unresolved [8] [4] [5]. Drugs.com and other patient‑facing summaries state ivermectin is not approved to treat cancer and there is “no high‑quality clinical evidence” that it shrinks tumors or improves survival [9]. Reports also note controversy from ivermectin’s high‑profile non‑oncology debates (COVID‑19) could bias public perception and clinical uptake [10].
5. What outcomes are missing from current reporting — larger randomized endpoints, toxicity at oncologic dosing
Available sources do not report any completed randomized controlled trials measuring standard oncology endpoints (progression‑free survival, overall survival) for ivermectin in cancer patients, nor do they report phase III results [4] [5]. There is limited published data on long‑term toxicity of ivermectin at proposed anticancer regimens in humans; reviews warn that safety at higher or prolonged dosing is not established [4] [9].
6. How clinicians and researchers are positioning the evidence — cautious interest, call for rigor
Professional reviewers urge cautious, evidence‑based investigation: preclinical promise justifies carefully designed clinical trials but not off‑label use outside trials. Gateway and OncoDaily describe the phase I/II TNBC trial as rational and ongoing; reviewers and patient‑education sites insist that robust phase III testing would be needed before adoption [2] [10] [9]. Some oncology voices express skepticism and note trials may be halted or need rigorous oversight [11].
7. Bottom line for patients and practitioners
Ivermectin has strong preclinical rationale and at least one investigator‑led phase I/II trial in metastatic TNBC reporting safety and preliminary clinical benefit signals [1] [2]. There is no high‑quality randomized clinical evidence demonstrating that ivermectin shrinks tumors or improves survival in humans; larger, controlled trials and formal toxicity data at oncologic doses remain absent in current reporting [4] [9]. Patients should not substitute ivermectin for proven cancer therapies outside a clinical trial [9].
Limitations: this summary relies solely on the provided sources; other unpublished or registry entries beyond these documents may exist and are not included here.