Fecal Microbiota Transplantation Shows Promise in Enhancing Cancer Immunotherapy Across Multiple Tumor Types
核心洞察
Two phase 1-2 clinical trials demonstrate that fecal microbiota transplantation (FMT) combined with immune checkpoint inhibitors achieves impressive response rates of 80% in non-small cell lung cancer and 75% in melanoma patients.
FMT from healthy donors successfully engrafts beneficial bacteria while eliminating harmful species from patients' baseline microbiomes, with bacterial loss being more predictive of treatment response than donor strain acquisition.
Safety profiles vary significantly by treatment regimen, with dual checkpoint inhibition showing earlier onset of severe adverse events, particularly when patients receive FMT from Prevotella-rich donors.
Two groundbreaking clinical trials have demonstrated that fecal microbiota transplantation (FMT) can significantly enhance the effectiveness of cancer immunotherapy, achieving remarkable response rates across multiple tumor types while revealing important insights about the gut microbiome's role in treatment outcomes.
Clinical Efficacy Across Cancer Types
The FMT-LUMINate phase 2 trial enrolled 40 patients across two cohorts, with 20 patients each having non-small cell lung cancer (NSCLC) and melanoma. In the NSCLC cohort, patients received FMT followed by pembrolizumab monotherapy, achieving an objective response rate (ORR) of 80% (95% confidence interval: 58.4–91.9), substantially exceeding the prespecified primary endpoint of 64%. The disease control rate reached 95%, with three of four non-responders experiencing stable disease lasting at least six months.
The melanoma cohort, treated with FMT followed by dual checkpoint inhibition with nivolumab and ipilimumab, demonstrated an ORR of 75% (95% confidence interval: 53.1–88.8), including 11 partial responses and four complete responses. At one-year follow-up, progression-free survival was 65% for NSCLC and 58% for melanoma patients, with overall survival reaching 100% and 79%, respectively.
A separate phase 1 trial (PERFORM) in metastatic renal cell carcinoma (mRCC) enrolled 20 patients who received encapsulated FMT (LND101) prior to immunotherapy-based regimens. Among 18 evaluable patients, nine (50%) achieved objective responses, including two complete responses, with 12 patients (67%) achieving clinical benefit defined as response or stable disease lasting at least six months.
Microbiome Remodeling Mechanisms
The trials revealed that treatment success depends more on eliminating harmful bacteria from patients' baseline microbiomes than on acquiring specific donor strains. Responding patients showed significantly higher magnitude of species-level genome bin (SGB) loss from baseline compared to non-responders (P = 0.016). The eliminated species included canonically harmful taxa associated with immunotherapy resistance, such as Enterocloster citroniae, Enterocloster bolteae, Clostridium innocuum, and Ruminococcus gnavus.
High-throughput culturomics validation in four responding patients confirmed that significantly more species were lost after FMT compared to those engrafted from donors (P = 0.029). Murine experiments further validated these findings, showing that reintroducing cocktails of eliminated bacteria into FMT-recipient mice inhibited anti-PD-1 (搜索) activity both as monotherapy (P = 0.028) and in combination with anti-CTLA-4 (搜索) (P = 0.022).
Responding patients demonstrated enrichment of beneficial bacteria including Faecalibacterium prausnitzii, Gemmiger formicilis, and Akkermansia muciniphila in NSCLC, while melanoma responders showed relative enrichment of Bacteroides eggerthii, Bacteroides faecis, and Alistipes senegalensis. Both cohorts exhibited enrichment of Oscillospiraceae family members, consistent with their previously reported association with favorable immunotherapy responses.
Safety Considerations and Donor Effects
Safety profiles varied significantly between treatment regimens. In the NSCLC cohort receiving anti-PD-1 (搜索) monotherapy, 85% of patients experienced any-grade adverse events, but no patients developed grade 3 or higher events. Only three patients required corticosteroids for grade 2 adverse events.
The melanoma cohort receiving dual checkpoint inhibition showed more concerning safety signals, with 95% experiencing any-grade adverse events and 60% developing grade 3 events. Notably, 15% of patients experienced myocarditis, with median onset of severe adverse events occurring at 40 days, earlier than previously reported in the literature.
Donor microbiome composition significantly influenced toxicity patterns. Unsupervised clustering identified two distinct donor clusters, with Cluster B characterized by high relative abundance of Prevotella species, including Segatella copri. All patients receiving FMT from Prevotella-rich donors in the melanoma cohort developed grade 3 or higher adverse events, and two of three myocarditis cases occurred in recipients of FMT from the same Prevotella-rich donor.
In the mRCC trial, patients with S. copri levels exceeding 10 counts per million at 10 weeks after FMT were more likely to develop grade 3 immune-related adverse events, but only among those receiving ipilimumab-containing regimens. This association was not observed in patients receiving anti-PD-1 (搜索) monotherapy, suggesting treatment-specific microbiome-toxicity interactions.
Metabolomic and Immune Correlates
Metabolomic profiling revealed distinct patterns between responders and non-responders. Non-responding patients showed significant increases in quinolinic acid and kynurenine, metabolites of the tryptophan pathway causatively linked to immunotherapy resistance. Patients with low bacterial loss exhibited higher plasma tryptophan concentrations after FMT (P = 0.004), while fecal tryptophan pathway metabolism decreased over time in responders.
High quinolinic acid levels correlated with reduced frequencies of circulating PD-1 (搜索)+CD8+ T cells and PD-1+CD45RA−CCR7− effector memory CD8+ T cells, while associating with increased CD127lowCD25highCD4+ effector memory regulatory T cells. These findings suggest that failure to eliminate baseline deleterious taxa sustains an immunosuppressive metabolic environment.
In the mRCC study, patients without grade 3 adverse events maintained significantly higher circulating levels of immune-supporting metabolites including cortisol, stearoylcarnitine, L-histidine, and citric acid cycle intermediates at 10 weeks after FMT. High levels of vitamin A, isocitric acid, and stearoylcarnitine correlated with treatment response and improved progression-free survival.
Clinical Implementation Considerations
The trials employed rigorous donor screening protocols, with healthy volunteers undergoing comprehensive medical history assessment, laboratory testing for transmissible pathogens, and exclusion criteria including metabolic diseases, recent antibiotic use, and gastrointestinal disorders. FMT was delivered via oral capsules containing 80-100 grams of donor feces, administered after polyethylene glycol bowel preparation and within one week before immunotherapy initiation.
Both studies established independent data safety monitoring committees that deemed the combinations safe according to predefined criteria, though the melanoma trial committee noted earlier onset of severe adverse events compared to historical controls. The identification of donor-specific toxicity patterns, particularly with Prevotella-rich donors in dual checkpoint inhibition settings, represents a critical finding for future trial design and patient safety.
These results establish FMT as a promising strategy for enhancing cancer immunotherapy effectiveness while highlighting the importance of donor selection and treatment regimen-specific considerations for optimizing both efficacy and safety outcomes.