73 Fasting mediated gut microbiome modulation improves response to immune checkpoint therapy in Renal Cell Cancer
Authors: BAri Shahla , Eysha Mostafa , Tannir Nizar , George Daniel , Conejo-Garcia Jose 
Published: August 2024

Abstract

Background
Gut microbiome and microbial metabolome has been shown to be a predictor and modulator of response to immune checkpoint blocker therapy (ICB) in clear cell renal cancer (ccRCC). Based on preliminary data from a prospective clinical study of 100 ccRCC patients, we showed differences in gut microbiome, microbial metabolome and progression free survival. Specifically higher abundance of indole acetic acid, indole acetaldehyde and indole pyruvic acid (IPyA), which represent microbial metabolism of tryptophan were significantly associated with immunotherapy resistance and shorter progression free survival.
We hypothesized that time restricted eating would favorably modulate the gut microbiome, microbial metabolome to improve ICB response.We therefore evaluated the efficacy and mechanism of time restricted eating to improve response to immune checkpoint therapy in preclinical kidney cancer models.

Methods
Specific pathogen free (SPF) BL6 mice were injected subcutaneously with 0.5X106 LVRCC67(Renal adenocarcinoma) cell lines to develop kidney cancer preclinical models followed by randomization into two equal groups when average tumor size reached 100 mm3. Both groups were treated with anti-mouse PD1 twice weekly and daily tyrosine kinase inhibitor (TKI) while group 1 was additionally started on 14 hours of daytime fast(corresponding to period of inactivity), with feeding restricted to ten hours at night, 3 days prior to start of systemic treatment. Tumor volumes were measured twice weekly to evaluate progression free survival (defined as 30% increase in tumor volume), and mice were euthanized at end point, defined as completion of eight doses of antiPD1 treatment.
To demonstrate that modulation of gut microbiome is the driving mechanism mediating favorable effect of TRE on ICB response, we conducted fecal microbiota transplant from fasting and non-fasting mice respectively into two groups of germ-free mice. Allowing two weeks for FMT to engraft, mice were injected with RenCa cell lines and subsequently treated with anti-mouse PD1 and TKI, without fasting, once tumors reached an average size of 100 mm 3.Tumors were measured twice weekly to assess PFS, until end point, defined similar to above.

Results
TRE was associated with significantly longer PFS via modulation of gut microbiome, which is necessary and sufficient to improve ICB response. Tumor growth was significantly slower and PFS significantly longer in SPF TRE mice as compared to non-TRE mice (median PFS 14 days vs 6 days, TRE vs non-TRE, p-0.02). Further GF mice engrafted with fasting microbiome developed significantly smaller tumors, which regressed after treatment, as opposed to those with non-fasting microbiota [(Mean tumor volume-45 mm3 vs 120 mm3, p-0.001 at day15 of injection), median PFS- not reached(NR) vs 7 days, P-0.007)].

Conclusions
TRE improves response to ICB in renal cell cancer and can be developed into a cost effective, adjunctive therapy to improve PFS and overall survival of ccRCC patients treated with ICB. Deeper understanding of TRE mediated changes in gut microbiome and microbial metabolome can be leveraged to improve ICB response in patients who are unable to fast.