image: C57BL/6 mice were injected with B16-F10 or MB49 cells and then treated with intramuscular PBS or AS01 at the specified days relative to tumor injection. (a) Experimental design for the B16-F10 melanoma model; (b) Mice received either two doses of PBS or one or two doses of 10 or 20 μg AS01 at days 0 and 4 after B16-F10 injection. Tumor volumes were monitored for 16 days after tumor inoculation (n = 7 mice for the PBS group, n = 9 for 10 μg AS01 single dose, n = 9 for 10 μg AS01 double dose, n = 10 for 20 μg AS01 single dose, n = 10 for 20 μg AS01 double dose); (c) Experimental design for the MB49 bladder cancer model. Only the double injection (day 0 + day 4) of the higher AS01 concentration was employed in the bladder cancer model; (d) Mice received either two doses of PBS or 20 μg AS01 at days 0 and 4 after MB49 injection; Tumor volumes were monitored for 13 days after tumor inoculation (n = 10 mice for the PBS group, n = 9 for the AS01 group) (e) Excised MB49 tumor weights at day 13 after tumor inoculation. Data are shown as mean ± SD, p values obtained by one-way ANOVA on day 16 tumor volumes (b) and two-way ANOVA (d) with Tukey’s multiple comparisons and unpaired t test (E), *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, and ****p ≤ 0.0001. PBS: phosphate buffered saline.
Credit: © Mihai G. Netea, et al. 2026. This is an Open Access article licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, sharing, adaptation, distribution and reproduction in any medium or format, for any purpose, even commercially, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
A new study published in Myeloid Cells (MC) reports that AS01, a vaccine adjuvant system best known for its use in AS01-adjuvanted vaccines, can induce trained immunity in human monocytes and reduce tumor growth in selected mouse cancer models.
Trained immunity refers to a form of long-term functional reprogramming in innate immune cells, enabling them to respond more strongly to later stimulation. In the study, researchers exposed human monocytes to AS01 and later challenged the cells with lipopolysaccharide. AS01-trained cells showed increased production of inflammatory cytokines, including IL-6 and TNF, after restimulation, suggesting enhanced innate immune responsiveness.
The researchers then tested AS01 in mouse models of melanoma, bladder cancer, and lung carcinoma. AS01 treatment reduced tumor growth in B16-F10 melanoma and MB49 bladder cancer models, while no comparable effect was observed in the Lewis lung carcinoma model. In responsive models, AS01 treatment was associated with changes in the tumor immune microenvironment, including increased frequencies of CD8+ T cells, neutrophils, and monocytes, together with a reduction in tumor-associated macrophages.
“These findings suggest that AS01 can induce a trained immunity phenotype and may have potential as a strategy to modulate antitumor immune responses,” the authors report. The study also highlights the need for further research to clarify the mechanisms involved, determine why responses differ across tumor models, and evaluate whether this approach could eventually inform cancer immunotherapy development.
The authors emphasize that the findings are preclinical and should not be interpreted as evidence of therapeutic efficacy in patients. Further studies will be required before any clinical application can be considered.
Method of Research
Experimental study
Subject of Research
Animals
Article Title
AS01 adjuvant is a trained immunity inducer with potent antitumor activity
Article Publication Date
21-Aug-2026
COI Statement
M.G.N. is a scientific founder of Trained Therapeutics and Discovery (TTxD), Lemba, Salvina, and Biotrip. The other authors declare no conflicts of interest.