Abnormalities in Clostridioides and related metabolites before ACTH treatment may be associated with its efficacy in patients with infantile epileptic spasm syndrome.

Objective: Adrenocorticotropic hormone (ACTH) is the first‐line treatment of infantile epileptic spasm syndrome (IESS). Its reported effectiveness varies, and our current understanding regarding the role of gut microbiota composition in IESS treatment response is limited. This study assessed the microbiome–metabolome association to understand the role and mechanism of gut microbiota composition in IESS treatment outcomes. Methods: Children with IESS undergoing ACTH treatment were enrolled. Pre‐treatment stool and serum samples were collected for 16S rRNA gene sequencing and liquid chromatography–tandem mass spectrometry, respectively. The children were divided into "responsive" and "non‐responsive" groups, and gut microbiota and serum metabolome differences were analyzed. Results: Of the 30 patients with IESS, 14 responded to ACTH and 16 did not. The "non‐responsive" group had larger maleficent Clostridioides and Peptoclostridium_phage_p630P populations (linear discriminant analysis >2; false discovery rate q < 0.05). Ten metabolites were upregulated (e.g., xanthurenic acid) and 15 were downregulated (e.g., vanillylmandelic acid) (p < 0.05). Association analysis of the gut microbiome and serum metabolome revealed that Clostridioides and Peptoclostridium_phage_p630P2 were positively correlated with linoleic and xanthurenic acids, while Clostridioides was negatively correlated with vanillylmandelic acid (p < 0.05). A classifier using differential gut bacteria and metabolites achieved an area under the receiver operating characteristic curve of 0.906 to distinguish responders from non‐responders. Conclusion: This study found significant differences in pre‐treatment gut microbiota and serum metabolome between children with IESS who responded to ACTH and those who did not. Additional exploration may provide valuable information for treatment selection and potential interventions. Our results suggest that varying ACTH responses in patients with IESS may be associated with increased gut Clostridioides bacteria and kynurenine pathway alteration, but additional experiments are needed to verify this association. [ABSTRACT FROM AUTHOR]