Ivermectin Outperforms 4 of 5 Chemo Drugs in 2026 Colon Cancer Lab Study
A June 2026 study from UC San Diego found ivermectin combined with recombinant methioninase outperformed four of five first-line chemotherapy drugs against colon cancer cells in vitro, with a chemosensitivity index of 6.7.
By Sanare Lab · July 2, 2026 · 6 min read
Key Takeaway
A June 2026 study from UC San Diego and AntiCancer Inc. found that ivermectin combined with recombinant methioninase (rMETase) outperformed four of five standard first-line chemotherapy drugs — including 5-fluorouracil, cisplatin, gemcitabine, and paclitaxel — when each was paired with rMETase against human colon cancer cells. This is in vitro (cell culture) research only; no human trials of this specific combination exist yet.
A June 2026 study from the University of California San Diego and AntiCancer Inc. tested ivermectin plus recombinant methioninase, an enzyme, against human colon cancer cells in a lab dish. This pair had a chemosensitivity index, a measure of cancer-cell response, of 6.7, beating the same enzyme paired with 5-fluorouracil, cisplatin, gemcitabine, and paclitaxel. Doxorubicin plus recombinant methioninase scored higher at 7.8. This was cell-culture research only, with no human trials yet.
Ivermectin's potential as an anticancer agent has been studied in preclinical models for over a decade, but a direct head-to-head comparison with standard chemotherapy drugs has rarely been attempted. A new study published in Frontiers in Oncology (June 2026) by researchers at AntiCancer Inc. and the University of California, San Diego, now provides exactly that: a systematic comparison of ivermectin versus five first-line chemotherapy drugs, all tested in combination with a novel enzyme called recombinant methioninase (rMETase).
The results are striking in the context of laboratory research: ivermectin combined with rMETase achieved a chemosensitivity index (CI) of 6.7 — significantly higher than the rMETase combinations with 5-fluorouracil (CI 2.0), cisplatin (CI 2.4), gemcitabine (CI 2.5), and paclitaxel (CI 2.8). Only doxorubicin combined with rMETase (CI 7.8) slightly outperformed the ivermectin combination.
Understanding what these numbers mean — and what they do not mean — is essential for anyone following this research area.
Table of Contents
- Study Overview
- What Is Recombinant Methioninase?
- Key Results
- How Ivermectin Fights Cancer Cells
- Limitations and Context
- FAQ
- Shop Sanare Lab
- References
Study Overview
The study was conducted by Kim J, Han Q, Li S, and colleagues at AntiCancer Inc. (San Diego) and the Department of Surgery at UC San Diego, with additional affiliation at Chungnam National University College of Medicine (South Korea). It was published on June 3, 2026 in Frontiers in Oncology.
| Parameter | Details |
|---|---|
| Study type | In vitro (cell culture) |
| Cancer type | Colorectal cancer (HCT116 human colon cancer cell line) |
| Drugs compared | Ivermectin, 5-FU, cisplatin, gemcitabine, paclitaxel, doxorubicin — all ± rMETase |
| Endpoint | Cell viability at 72h (WST-8 assay); Chemosensitivity Index (CI) |
| Institution | AntiCancer Inc. + UC San Diego, USA |
| Published | June 3, 2026 — Front Oncol, DOI: 10.3389/fonc.2026.1807785 |
What Is Recombinant Methioninase?
Recombinant methioninase (rMETase) is an enzyme derived from bacteria that degrades methionine — an essential amino acid that cancer cells require in unusually large amounts. This phenomenon, known as "methionine addiction" or the Hoffman effect, was first described by Robert Hoffman (the senior author of this study) in the 1970s. Cancer cells cannot survive without an external methionine supply, while normal cells can synthesize methionine from homocysteine.
By depleting methionine, rMETase selectively starves cancer cells while sparing normal tissue. When combined with conventional chemotherapy or other anticancer agents, rMETase has shown synergistic effects in multiple preclinical studies. The current study is the first to systematically compare ivermectin's performance in this rMETase combination framework against five standard chemotherapy drugs.
Key Results: Ivermectin vs. Standard Chemotherapy
The chemosensitivity index (CI) measures how much a drug combination reduces cancer cell viability relative to the drug alone. A higher CI means the combination is more effective than the drug alone — i.e., rMETase adds more benefit to that drug.
| Drug | CI with rMETase (mean ± SD) | vs. Ivermectin+rMETase |
|---|---|---|
| Ivermectin | 6.7 ± 1.9 | — |
| Doxorubicin | 7.8 ± 1.7 | Slightly higher (not significant) |
| Paclitaxel | 2.8 ± 0.5 | Significantly lower (p<0.05) |
| Gemcitabine | 2.5 ± 0.7 | Significantly lower (p<0.05) |
| Cisplatin | 2.4 ± 1.5 | Significantly lower (p<0.05) |
| 5-Fluorouracil | 2.0 ± 0.7 | Significantly lower (p<0.05) |
The authors conclude: "Ivermectin combined with rMETase was more effective than four of five first-line chemotherapy drugs combined with rMETase against colon-cancer cells, demonstrating additional promise of ivermectin as an anticancer drug."
How Ivermectin Fights Cancer Cells
Ivermectin's anticancer mechanisms are distinct from its antiparasitic action and have been studied across multiple cancer types. The drug appears to work through several parallel pathways:
- P-glycoprotein inhibition: Ivermectin blocks the P-gp drug efflux pump that cancer cells use to expel chemotherapy drugs, potentially restoring sensitivity to conventional treatment.
- Chloride channel activation: Ivermectin activates glutamate-gated chloride channels, disrupting ion homeostasis in cancer cells.
- Oncogenic signaling inhibition: Multiple studies have shown ivermectin can suppress Wnt/beta-catenin, PI3K/Akt/mTOR, and YAP/TAZ signaling pathways that drive cancer cell proliferation and survival.
- Mitotic arrest: Ivermectin has been shown to interfere with cell division in cancer cells.
- Methionine pathway synergy: The current study suggests ivermectin may have particular synergy with methionine depletion, though the exact mechanism of this interaction requires further investigation.
Limitations and Context
Several important caveats apply to this study:
- Single cell line: All experiments used the HCT116 colon cancer cell line. Results may not generalize to other colorectal cancer subtypes or other cancer types.
- In vitro only: Cell culture experiments do not account for pharmacokinetics, drug metabolism, immune system interactions, or tumor microenvironment effects in living organisms.
- rMETase is not clinically available: Recombinant methioninase is an experimental enzyme not approved for clinical use. The combination tested here cannot be replicated in a clinical setting at this time.
- Conflict of interest note: Author QH was employed by AntiCancer Inc., which has a commercial interest in rMETase development. The other authors declared no conflicts. This does not invalidate the findings but warrants awareness.
- No human data: No clinical trials of ivermectin + rMETase in colorectal cancer patients exist.
For background, see our guide to how ivermectin works.
We cover this in more depth in our article on ivermectin cancer protocols and dosing.
Estimate a weight-based regimen with our protocol calculator.
Frequently Asked Questions
What is the chemosensitivity index (CI) and what does a higher number mean?
The chemosensitivity index (CI) in this study is defined as the ratio of cancer cell viability after treatment with a drug alone (at its IC50) to cell viability after treatment with the same drug combined with rMETase. A higher CI means the combination is more effective than the drug alone — rMETase adds more killing power to that drug. A CI of 6.7 for ivermectin means the combination killed approximately 6.7 times more cells than ivermectin alone at the same concentration.
Does this study prove ivermectin is better than chemotherapy for colon cancer?
No. This is a cell culture study comparing how well different drugs work in combination with rMETase — an experimental enzyme not available in clinical practice. It does not compare ivermectin to chemotherapy in patients, and it does not measure survival, tumor shrinkage, or any clinical endpoint. The study demonstrates that ivermectin has interesting synergy with rMETase in this laboratory model, which justifies further research.
What is methionine addiction in cancer cells?
Cancer cells have an unusual metabolic dependency on the amino acid methionine — they cannot survive without an external supply, unlike normal cells which can synthesize methionine from homocysteine. This phenomenon, called the Hoffman effect or methionine dependence, was first described in the 1970s. Recombinant methioninase exploits this vulnerability by depleting methionine in the tumor environment, selectively starving cancer cells.
Are there clinical trials of ivermectin for colorectal cancer?
As of 2026, there are no completed Phase III clinical trials of ivermectin specifically for colorectal cancer. Several early-phase trials have investigated ivermectin in various cancer types, including a notable trial (NCT05318469) examining ivermectin combined with immunotherapy. The preclinical evidence base for ivermectin in colorectal cancer is growing, but clinical validation remains limited.
Who conducted this research and is there a conflict of interest?
The study was conducted by researchers at AntiCancer Inc. (San Diego), UC San Diego, and Chungnam National University (South Korea). Author QH was employed by AntiCancer Inc., which has a commercial interest in developing rMETase. The other authors declared no conflicts of interest. The study was published in Frontiers in Oncology, a peer-reviewed journal, and the methodology is transparent and reproducible.
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References
- Kim J, Han Q, Li S, et al. Direct comparison of efficacy of combining ivermectin versus five first-line chemotherapy drugs with recombinant methioninase against colon-cancer cells. Front Oncol. 2026;16:1807785. doi:10.3389/fonc.2026.1807785. PMID: 42318457. PubMed
- Hoffman RM. Development of recombinant methioninase to target the general cancer-specific metabolic defect of methionine dependence: a 40-year odyssey. Expert Opin Biol Ther. 2015;15(1):21-31. doi:10.1517/14712598.2015.963050.
- Juarez M, Schcolnik-Cabrera A, Dueñas-Gonzalez A. The multitargeted drug ivermectin: from an antiparasitic agent to a repositioned cancer drug. Am J Cancer Res. 2018;8(2):317-331. PMID: 29511601.
Medical Disclaimer
This article is for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
Sanare Lab
Science-based health education team reviewing published research on repurposed drugs, integrative oncology, and evidence-based protocols.