Immunotherapy advances have transformed multiple myeloma treatment in recent years. Among these innovations, BCMA-targeted CAR-T cell therapy represents one of the most promising strategies for patients with relapsed or refractory disease. However, even with deep responses, many patients still experience relapses. For this reason, researchers are looking for biological factors capable of explaining differences in clinical outcomes.
In this context, the study “Microbiota Shape Metabolic and Immune Determinants of CAR-T Therapy and Correlate with Outcomes in Multiple Myeloma,” published in the journal Blood Cancer Discovery in 2025, brought important evidence regarding the influence of the intestinal microbiota, microbiota-derived metabolites, and the immune response on the efficacy of CAR-T therapy. The results suggest that metabolic and immune determinants of the microbiota shape CAR-T therapy and are associated with the persistence of modified cells, depth of response, and patient survival.
Furthermore, the research reinforces a growing trend in modern oncology: understanding the patient in an integrated manner, considering not only the tumor but also the biological ecosystem that influences immunity.
What is the intestinal microbiota and why does it matter?
The intestinal microbiota corresponds to the collection of microorganisms that inhabit the human gastrointestinal tract. This ecosystem includes bacteria, viruses, fungi, and other microorganisms that coexist in balance with the body.
For many years, it was believed that these microbial communities had a function limited to digestion. However, recent studies have demonstrated that the microbiota actively participates in immune regulation, energy metabolism, and the production of bioactive molecules.
Moreover, several intestinal bacteria produce metabolites capable of directly influencing the activity of immune cells. Thus, changes in microbial composition can modify the body’s response against infections, inflammatory diseases, and cancer.
For this reason, understanding the interaction between the microbiota and immunotherapy has become a strategic area of research.
Metabolic and immune determinants of the microbiota shape CAR-T therapy
The study evaluated patients with multiple myeloma treated with the BCMA-directed CAR-T therapy ARI0002h. Researchers collected stool and blood samples before cell infusion and analyzed various microbiological, metabolic, and immunological parameters.
The results demonstrated that certain bacterial families and metabolites had a significant association with important characteristics of CAR-T cells.
Additionally, some of these biological signatures were related to the persistence of the therapeutic cells after infusion and the achievement of a complete response to treatment.
These findings reinforce the hypothesis that metabolic and immune determinants of the microbiota shape CAR-T therapy through the modulation of the immune system and cellular metabolism.
Microbiota stability before infusion
One of the first findings of the research was the stability of the microbiota between the time of apheresis and the lymphodepletion period.
Researchers observed that the bacterial composition and metabolic profile remained relatively constant during this interval. Therefore, the characteristics identified before infusion reflected a consistent biological state of the patient.
This data is relevant because it increases the reliability of the associations found between the microbiota and the therapeutic response.
How do metabolites influence CAR-T cells?
T cells depend on intense energy metabolism to maintain their capacity for proliferation and tumor elimination.
Consequently, metabolites produced by the microbiota can directly interfere with their functionality.
Among the analyzed compounds, succinate stood out as one of the most relevant.
The role of succinate
Researchers identified a positive correlation between fecal succinate levels and the presence of CD4+ central memory T cells.
These cells are considered highly desirable in CAR-T products because they exhibit a greater capacity for expansion and persistence in the body.
Furthermore, succinate showed a positive association with the persistence of CAR-T cells one hundred days post-infusion.
To investigate this effect, the authors conducted laboratory experiments adding succinate to the cell expansion process in ex vivo experiments.
The results demonstrated:
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An increase in central memory T cells;
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A reduction in more differentiated effector cells;
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An improvement in mitochondrial respiratory capacity;
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A potential increase in cell persistence.
Therefore, succinate emerges as a promising candidate in preclinical models for future strategies to optimize the manufacturing of CAR-T therapies.
Evidence in animal models
In addition to in vitro experiments, the researchers evaluated mice with multiple myeloma.
The animals received a diet supplemented with fructooligosaccharides, an intervention associated with changes in the intestinal microbiota and an increase in certain metabolites, including succinate.
As a result, greater persistence of CAR-T cells and a tendency toward better tumor control were observed.
Although more studies are needed, the data suggest that nutritional interventions could in the future contribute to boosting immunotherapy.
Microbial diversity and clinical response
Another important aspect identified was the relationship between microbial diversity and therapeutic efficacy.
Patients who achieved a complete response presented greater intestinal microbiota diversity before infusion.
This result aligns with previous observations across different immunotherapy modalities.
Furthermore, individuals with multiple myeloma showed significantly lower diversity when compared to healthy volunteers.
This reduction in diversity may reflect:
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Cumulative effects of previous treatments;
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Metabolic changes associated with cancer;
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Chronic inflammation;
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Frequent use of antibiotics.
Consequently, the loss of diversity may contribute to less efficient immune responses.
Bacteria associated with the best outcomes
The research identified bacterial groups related to favorable responses.
Among them, the following stand out:
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Acidaminococcaceae: This bacterial family showed a strong association with a complete response at 100 and 180 days after infusion. Furthermore, the predictive model developed by the researchers identified this family as one of the main markers of therapeutic efficacy.
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Barnesiellaceae: The abundance of this family was also related to deeper responses. Previous studies had already suggested its role in immune modulation and the recovery of the microbiota following aggressive treatments.
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Akkermansiaceae: Although better known for its association with immunotherapies based on checkpoint inhibitors, this family also appeared in the models related to the positive evolution of the CAR-T response. Therefore, its role warrants additional investigation in future clinical trials.
Bacteria associated with worse responses
Likewise, some bacterial families showed a correlation with lower therapeutic efficacy.
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Monoglobaceae: Patients who did not achieve a complete response presented a greater abundance of this bacterial family. Additionally, its presence repeatedly appeared in predictive models associated with less favorable outcomes.
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Erysipelatoclostridiaceae: This family was also associated with inferior responses and a greater intensity of cytokine release syndrome within the analyzed cohort. Therefore, it may represent a relevant biomarker for risk stratification.
Metabolites associated with therapeutic response
Metabolomic analysis revealed important differences between patients with a complete response and those with less deep responses.
Among the most relevant metabolites, the following stand out:
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Methionine;
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Phenylalanine;
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Tyrosine;
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Inosine;
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Succinate.
Interestingly, higher concentrations of methionine, phenylalanine, and tyrosine were observed in patients who did not achieve a complete response.
On the other hand, higher levels of succinate showed a favorable association with cell persistence and better clinical outcomes.
These results suggest that microbial metabolism can modulate the patient’s immune environment.
Predictive models for therapy personalization
One of the most innovative aspects of the study was the construction of predictive models integrating:
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Microbiota data;
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Fecal metabolites;
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Serum metabolites;
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Clinical information;
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Immunological characteristics.
The models achieved a high capacity to identify patients with a higher probability of a complete response.
Furthermore, the researchers validated part of these analyses in a second independent cohort.
This result paves the way for increasingly personalized medicine.
In the future, it will be possible to use microbial biomarkers to identify patients who may benefit from complementary strategies before CAR-T infusion.
Implications for the future of CAR-T therapy
The discoveries of this study possess significant practical relevance.
First, they demonstrate that factors external to the tumor can influence the efficacy of immunotherapy.
Additionally, they suggest that microbiota-directed interventions may improve clinical outcomes.
Among the strategies currently being investigated are:
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Dietary modulation: Specific diets can favor the growth of beneficial bacteria. Furthermore, nutrients capable of increasing the production of favorable metabolites can contribute to better immune performance.
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Precision probiotics: Unlike conventional probiotics, this approach seeks to administer bacterial strains selected based on scientific evidence.
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Prebiotics: Prebiotics provide substrates for the growth of beneficial microorganisms. Consequently, they can increase the production of metabolites associated with the immune response.
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Fecal microbiota transplantation: Although still experimental in oncology, this strategy already demonstrates the potential to restore microbial ecosystems associated with better immune responses.
Influence on the future of oncology
The study published in Blood Cancer Discovery offers robust evidence that the intestinal microbiota influences fundamental aspects of CAR-T therapy in patients with multiple myeloma.
The data show that certain bacterial groups and metabolites are associated with the composition of CAR-T cells, cell persistence, clinical response, and long-term outcomes.
Furthermore, succinate emerges as a particularly relevant metabolite, capable of favoring characteristics associated with therapeutic efficacy.
Thus, the integration of microbiology, immunology, and metabolomics represents a new frontier in precision oncology.
In the coming years, strategies aimed at modulating the microbiota may complement CAR-T therapy, expanding its efficacy and contributing to even better outcomes for patients with multiple myeloma.
References:
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URIBE-HERRANZ, Mireia et al. Microbiota Shape Metabolic and Immune Determinants of CAR-T Therapy and Correlate with Outcomes in Myeloma. Blood Cancer Discovery, v. 6, p. 484–504, 2025.
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JUNE, C. H.; SADELAIN, M. Chimeric antigen receptor therapy. New England Journal of Medicine, v. 379, p. 64–73, 2018.
SEO Keywords: intestinal microbiota, CAR-T therapy, multiple myeloma, cellular immunotherapy, succinate, microbial metabolites, immune response, memory T cells, BCMA, CAR-T persistence, metabolomics, microbiome, microbial diversity, advanced cell therapy, precision oncology.
