What randomized controlled trials have evaluated repurposed antiparasitic drugs (ivermectin, mebendazole) in cancer and what were their dosing regimens?
Executive summary
A comprehensive review of the available reporting shows no completed randomized, placebo‑controlled trials that prove ivermectin or mebendazole are effective cancer therapies; the literature instead contains case reports, early‑phase or simulated dose‑finding studies, and a small number of investigator‑initiated clinical trials and protocols still in progress [1] [2] [3]. Reported human dosing in these sources ranges widely—from antiparasitic doses (single‑digit milligrams daily) to community‑circulated “high‑dose” protocols (up to ~1–2 mg/kg/day for ivermectin and hundreds of mg/day for mebendazole)—but these regimens are largely anecdotal or come from non‑randomized/early‑phase work rather than randomized controlled trials [4] [5] [6].
1. What the randomized‑trial landscape actually looks like
No source in the provided reporting documents a completed randomized controlled trial (RCT) demonstrating anticancer efficacy of ivermectin or mebendazole in cancer patients; Science Feedback explicitly concluded that publications cited to support clinical protocols do not provide RCT evidence for cancer indications and that the referenced ivermectin trials were safety studies in healthy people or commentary, not cancer RCTs [1]. The bulk of human data available in these reports are case series, single‑arm early‑phase cohorts or simulated dose‑finding exercises rather than randomized comparisons against standard care or placebo [2] [3] [6].
2. Early‑phase and investigator trials referenced (non‑randomized)
There are several early‑phase or investigator‑led efforts: a reported Phase I/II trial (NCT05318469) combining ivermectin with the anti‑PD‑1 agent balstilimab in metastatic triple‑negative breast cancer was described as reporting safety and encouraging clinical benefit rates at ASCO 2025, but that is an early, non‑randomized signal rather than an RCT result [2]. The National Cancer Institute lists a trial pairing ivermectin with pembrolizumab (NCI identifier shown in the registry), which represents institutional interest but is not presented in the sources as a completed randomized trial [7]. A simulated hybrid Phase I/II dose‑escalation for ivermectin plus mebendazole was reported as a modeling exercise with a small Phase II cohort—again, not a randomized RCT [3].
3. What dosing regimens appear in trials, simulations and reports
Dosing recommendations in the literature and online protocols vary dramatically and often lack randomized validation: OneDayMD and related community protocols cite ivermectin regimens from 24 mg daily up to “1 mg/kg/day” for aggressive cancers and anecdotal reports of doses as high as 2 mg/kg/day, while mebendazole is reported in community and case reports at 100 mg twice daily or 200–400 mg/day and fenbendazole commonly at ~300 mg several days per week [4] [5] [6]. The phase‑1 glioma study combining mebendazole with temozolomide reportedly escalated mebendazole to very high levels in that trial context—sources state escalation from 25 to 200 mg/kg/day divided three times daily—though this was a small, non‑randomized dose‑finding study and not an RCT [6]. Guzzo et al.’s safety study of high‑dose ivermectin in healthy adults is often cited for tolerability data but was not a cancer trial and thus does not establish oncologic dosing or efficacy [1].
4. How to interpret these dosing numbers and the evidence quality
The diversity of reported regimens reflects a mix of anecdote, compassionate‑use practice, early‑phase dose escalation and simulation rather than standardized, randomized evidence; community protocols frequently extrapolate from preclinical synergy models and small human cohorts without randomized controls, creating selection and reporting biases that the reviews warn about [2] [8] [9]. Science Feedback and other reviewers emphasize that preclinical promise and healthy‑volunteer safety studies do not substitute for RCTs in determining whether a dose is effective and safe for cancer patients [1].
5. Bottom line and gaps that matter to patients and researchers
There are no definitive randomized controlled trials in the provided reporting that establish an ivermectin or mebendazole regimen for cancer; ongoing early‑phase work and registry trials suggest active investigation, and widely circulated high‑dose protocols exist online, but they remain unsupported by randomized efficacy data and carry uncertain safety profiles at elevated doses [2] [3] [4]. The sources collectively call for properly designed randomized trials to define safe, effective dosing and to avoid reliance on uncontrolled anecdotes [2] [1] [9].