A non-NIH clinical trial is now testing ivermectin, the antiparasitic drug that became a lightning rod during the COVID-19 pandemic, as a potential weapon against one of the most aggressive forms of breast cancer. The trial pairs ivermectin with checkpoint inhibitor immunotherapies to treat metastatic triple-negative breast cancer, a disease with limited treatment options and poor survival rates. This is not a fringe effort or a social media campaign. It is a registered Phase 1 clinical study, and it forces a serious question about whether a drug dismissed by many during the pandemic could find legitimate new purpose in oncology.
A Phase 1 Trial With a Familiar Name
The study, formally titled “Ivermectin in Combination With Balstilimab or Pembrolizumab in Patients With Metastatic Triple Negative Breast Cancer,” is listed on the federal trial registry maintained by the U.S. National Library of Medicine, part of the NIH. Its identifier is NCT05318469, and the listing on ClinicalTrials.gov describes a Phase 1 design, meaning its primary goal is to evaluate safety and dosing rather than to prove large-scale effectiveness. Phase 1 trials are the earliest stage of human testing, typically enrolling small numbers of patients to determine whether a drug or combination can be tolerated before larger studies proceed.
What makes this trial unusual is its central ingredient. Ivermectin earned worldwide notoriety during the pandemic as an unproven COVID-19 treatment, championed by some patient advocacy groups and politicians while being sharply criticized by the FDA and mainstream medical organizations. The drug is well established as an antiparasitic, used for decades to treat conditions like river blindness and scabies in carefully controlled doses. Its proposed use in oncology represents a different scientific question entirely, one grounded in preclinical observations about how ivermectin may interact with cancer cell biology rather than in its antiviral reputation. By putting ivermectin into a formal oncology protocol, investigators are treating it like any other experimental component, a molecule with hypothesized mechanisms that must be tested under controlled conditions.
Why Triple-Negative Breast Cancer
Triple-negative breast cancer accounts for roughly 10 to 15 percent of all breast cancer diagnoses, according to widely cited oncology estimates, and it is defined by what it lacks: the three receptors (estrogen, progesterone, and HER2) that many targeted therapies depend on. That absence makes it harder to treat than other breast cancer subtypes, because hormonal therapies and HER2-directed drugs are largely ineffective. When the disease becomes metastatic, meaning it has spread beyond the breast to organs such as the lungs, liver, or brain, treatment options narrow further. Standard chemotherapy remains the backbone of care, but response rates drop over time and recurrence is common, leaving many patients cycling through regimens with diminishing benefit.
The trial’s design pairs ivermectin with either balstilimab or pembrolizumab, both checkpoint inhibitors that target immune pathways involved in T cell activation. These drugs work by releasing the brakes on the immune system, allowing T cells to recognize and attack tumor cells more effectively. The hypothesis behind adding ivermectin appears to be that it could modulate the tumor microenvironment or cancer cell signaling in ways that make immune attack more likely, potentially enhancing the effect of the checkpoint inhibitor. At this Phase 1 stage, that idea is speculative, and the protocol’s primary purpose is to confirm whether the combination is safe, not to prove it works. But the choice of disease target is telling: triple-negative breast cancer is exactly the kind of hard-to-treat malignancy where researchers are willing to explore unconventional combinations because the status quo leaves many patients with few good options.
NIH’s Track Record Testing COVID-Era Drugs
The NIH has significant experience running rigorous trials for drugs that gained attention during the pandemic, including those that were initially surrounded by controversy or uncertainty. The agency launched a major randomized clinical trial for remdesivir, the antiviral that became one of the first authorized treatments for hospitalized COVID-19 patients. That effort, known as ACTT-1, enrolled 1,062 participants in a randomized, controlled design and ultimately produced a final report published in the New England Journal of Medicine confirming that remdesivir shortened recovery time in hospitalized patients. The NIH summary of those findings emphasizes that the benefit was modest but real, and that it emerged only after carefully collected data were analyzed and peer-reviewed.
The remdesivir experience illustrates how NIH-run trials move from registry entry to peer-reviewed evidence. The National Institute of Allergy and Infectious Diseases publicly announced the launch of the remdesivir trial, enrolled patients across multiple sites, and followed the standard pathway from early readouts to a final, fully vetted publication. That infrastructure, built and refined under the intense pressure of the COVID-19 emergency, now provides a template for how the ivermectin cancer trial could progress if early results warrant further study. The difference, of course, is that remdesivir was being tested for its intended role as an antiviral, while ivermectin is being repurposed for a completely different disease category, with distinct biological questions and safety considerations.
Drug Repurposing and Its Limits
Repurposing existing drugs for new diseases is not a new idea, but it carries real scientific and public perception risks. Thalidomide, once infamous for causing birth defects when given to pregnant women, was later approved to treat multiple myeloma after researchers identified anti-angiogenic and immunomodulatory properties that were relevant to cancer. Metformin, a long-standing diabetes drug, is being studied in cancer prevention and treatment trials because of its effects on insulin signaling and cellular metabolism. The appeal of repurposing is straightforward: these drugs already have established safety profiles in at least one population, manufacturing processes, and regulatory histories, which can shorten the timeline and reduce the cost of bringing a therapy to patients. For a disease as difficult as metastatic triple-negative breast cancer, even a modest improvement in outcomes could matter, especially if it can be delivered with an oral agent that is relatively inexpensive.
But ivermectin carries baggage that metformin and thalidomide did not when they entered modern oncology research. The pandemic-era controversy around its use as a COVID-19 treatment created deep polarization, with some patients turning to veterinary formulations without medical supervision and public health agencies spending significant resources warning against unproven use. That history means any legitimate scientific finding about ivermectin in cancer will be filtered through a lens of suspicion on one side and vindication on the other, regardless of what the data actually show. Researchers running this trial will need to be especially clear about what a Phase 1 study can and cannot prove: it can reveal dose-limiting toxicities, drug–drug interactions, and preliminary signals of activity, but it cannot settle debates about overall survival or justify off-label prescribing outside a trial.
Reputation, Evidence, and What Comes Next
The dominant assumption in much current public discourse, that ivermectin’s pandemic notoriety automatically discredits any new research involving the drug, deserves pushback. Science does not work by reputation. A molecule’s pharmacological properties do not change because it was misused or overhyped in a different context, and prior controversy neither guarantees failure nor assures success in a new indication. What matters is whether the preclinical rationale is coherent, whether the study design can actually test the relevant hypotheses, and whether the results are reported transparently. In that sense, placing ivermectin into a formal oncology trial is a way of moving the conversation from social media arguments to data-driven assessment, with independent oversight and predefined endpoints.
That does not mean patients should view the trial as proof that ivermectin “works” against cancer, or that self-medication is wise or safe. The history of oncology is filled with agents that looked promising in early-stage studies but failed to deliver benefit in larger trials, as well as drugs that were ultimately too toxic in combination with other therapies. The appropriate takeaway is more modest: ivermectin has cleared enough preliminary scientific and regulatory hurdles to justify a small, carefully monitored Phase 1 study in a population with urgent unmet need. Whether it progresses beyond that will depend entirely on what the data show, not on the political and cultural battles that once swirled around its name. In the meantime, the trial stands as a reminder that even the most controversial drugs can, and should, be subjected to the same rigorous standards of evidence as any other candidate therapy.
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*This article was researched with the help of AI, with human editors creating the final content.
