Written from the studies on PubMed, searched on 13 Nov 2026. Every number below comes from a study listed under Sources. The text was written by AI from these studies; each sentence names the studies it comes from.
The claim
Posts say that blocking lactate, a waste product of tumour cells, can be used to fight cancer.
Where research stands
We found 18 published papers on lactate targeting and cancer. They were published between 2013 and 2023. 1 of them is a study in people. In all, 40 people took part. None of them compared people who got it with a group that did not. 11 were studies in animals, and 2 were only in cells in the lab. 1 paper is a review that sums up other studies.
- 1In people
- 11In animals
- 2Only in the lab
What the studies found
Trials in people
There is one trial in people. It tested a pill that blocks lactate in 40 people with advanced cancer. [1] It was a first small test in people, mainly to check safety. [1] It did not aim to show the pill works against cancer. [1] Most side effects were mild, like eye test changes, tiredness and constipation. [1] Seven people on higher doses had serious side effects. [1]
Other studies in people
One man with melanoma became very ill with too much lactate in his blood after his first dose. [2] His body was already out of balance before the drug. [2] He died two months later. [2] The trial then stopped taking people with high lactate. [2]
Reviews
A review of animal and lab work found the drug slowed tumour growth. [3] It worked best when combined with other treatments. [3] Tumour cells that make another lactate carrier can resist the drug. [3]
In animals
In mice with lymphoma, the drug cut tumour growth. [4][5] In mice with breast tumours, the results were mixed. [6] The cancer spread more to the lung, and white blood cell counts fell. [6] In bladder cancer, it worked only in cells with low levels of the other carrier. [7] Results in animals do not always hold in people.
In the lab
In lymphoma cells with little of the other carrier, the drug strongly slowed growth. [4] In breast cancer cells, it worked better with a lab-made metal compound. [9] That combination has not been tried in people. [9]
Verdict
The only test in people was a small safety study, not a test of benefit. [1] Animal and lab results are mixed, and one patient died after a severe reaction. [6][2] Nothing yet shows it helps people with cancer, so the claim is unproven. [1][3]
Unproven means: it was only tested in animals or cells, or there is too little or mixed data from people. How we rate claims
What this means for you: A study in people is not proof that it helps you. Do not stop or change your medicines because of it. Ask your doctor before you start taking it.
Sources
- A Phase I Dose-escalation Study of AZD3965, an Oral Monocarboxylate Transporter 1 Inhibitor, in Patients with Advanced Cancer.2023 · Clin Cancer Res · Study in people
- A case of malignant hyperlactaemic acidosis appearing upon treatment with the mono-carboxylase transporter 1 inhibitor AZD3965.2020 · Br J Cancer · Other paper
- In Vivo Anticancer Activity of AZD3965: A Systematic Review.2021 · Molecules · Review
- Inhibition of monocarboxyate transporter 1 by AZD3965 as a novel therapeutic approach for diffuse large B-cell lymphoma and Burkitt lymphoma.2017 · Haematologica · In the lab
- Monocarboxylate transporter 1 blockade with AZD3965 inhibits lipid biosynthesis and increases tumour immune cell infiltration.2020 · Br J Cancer · In animals
- In Vitro and In Vivo Efficacy of AZD3965 and Alpha-Cyano-4-Hydroxycinnamic Acid in the Murine 4T1 Breast Tumor Model.2020 · AAPS J · In animals
- Effects of Lactate Transport Inhibition by AZD3965 in Muscle-Invasive Urothelial Bladder Cancer.2023 · Pharmaceutics · In animals
- In Vitro and In Vivo Characterization of MCT1 Inhibitor AZD3965 Confirms Preclinical Safety Compatible with Breast Cancer Treatment.2021 · Cancers (Basel) · In animals
- Targeting cancer lactate metabolism with synergistic combinations of synthetic catalysts and monocarboxylate transporter inhibitors.2023 · J Biol Inorg Chem · Other paper
