Gut check.

Two studies in this week’s Science are blowing our minds…and bowels. They both ask how the gut microbiome influences the efficacy of PD-1 inhibitors. The first study looked at over 200 patients receiving PD-1 inhibitors and compared outcomes for those who did or did not take antibiotics (for whatever reason) during their treatments. And it seems, if you took antibiotics, you had worse cancer responses. In the other study, patients with melanoma and good responses to PD-1 inhibitors had more diverse microbiomes than non-responders. Here’s where things get interesting, but weird. In both studies, germ-free mice were fed stool (it’s more appealing if you say “schtool”) from human responders and non-responders. Mice that got responder stool had good PD-1 responses. The other mice, well, just had to eat poop. The authors homed in on Akkermansia muciniphila as the possible mediator of these effects, hypothesizing that the organism enhances T-cell response to PD-1 therapy. Why is this important? First, you may wanna avoid antibiotics in people on immunotherapy. Second, you can actually buy probiotics with A. muciniphila. More broadly, gut bacteria is going to start being taken more seriously as we all digest the data supporting their role in the fight against cancer.