Role of the intestinal microbiome and microbial-derived metabolites in immune checkpoint blockade immunotherapy of cancer

Table 1 The microbial-derived metabolites and ICI responses in clinical studies

Metabolites	Patient (n)	Disease	ICIs	Effects	References
SCFAs • Fecal acetate (high) • Fecal propionate (high) • Fecal butyrate (high) • Fecal valeric acid (high) • Plasma isovaleric acid (high)	52	Solid cancer tumor	Anti-PD-1	Longer PFS	[48]
SCFAs • Fecal propionate (high) • Fecal butyrate (high) Fecal lysine (high) Fecal nicotinic acid (high)	11	NSCLC	Anti-PD-1	Longer responses	[49]
SCFAs • Plasma butyrate (high)	40	Metastatic melanoma Metastatic prostate carcinoma	Anti-CTLA-4	Shorter PFS	[50]
SCFAs • Plasma propionate (high)	45	Metastatic melanoma	Anti-CTLA-4	Shorter PFS	[50]
Serum kynurenine/tryptophan ratio (high)	106	Advanced melanoma Advanced RCC	Anti-PD-1	Shorter OS	[52]
3-Hydrozyanthranilic acid (low)	19	NSCLC		Longer PFS	[53]
Fecal 2-pentanone (high) Fecal tridecane (high)	11	NSCLC	Anti-PD-1	Early progression	[49]
Serum IDO	23	NSCLC	Anti-PD-1	ICI resistance	[55]

ICI, immune checkpoint inhibitor; IDO, indoleamine-2,3-diozygenase; NSCLC, non-small cell lung cancer; OS, overall survival; PFS, progression-free survival; RCC, renal cell carcinoma

ISSN: 1756-994X