medwireNews: Preliminary research presented at the 2021 ASCO Annual Meeting suggests that use of a bacterial product might improve response to checkpoint inhibitor therapy in patients with metastatic renal cell carcinoma (RCC).
Lead author Luis Meza (City of Hope Comprehensive Cancer Center, Duarte, California, USA) delivered in a poster discussion session the phase 1b trial findings for CBM-588, a live bacterial product made from Clostridium butyricum that is postulated to alter the gut microbiome and/or immunomodulate the gut.
Patients with at least two sites of metastatic RCC were randomly assigned to receive four cycles of nivolumab plus ipilimumab therapy every 3 weeks followed by monthly nivolumab maintenance, given with or without CBM-588 as an 80 mg oral supplement twice daily.
The primary endpoint of a change in several species of Bifidobacterium after 12 weeks of treatment was evaluated in 19 patients given CBM-588 and 10 controls.
Paired stool specimens showed that patients given the bacterial product had a change in their microbiome composition, with nonsignificant increases in Bifidobacterium, Bifidobacteriales and Bifidobacteriaceae.
By contrast, patients given nivolumab plus ipilimumab without the bacterial product had a decrease in all three and, unlike their counterparts given CBM-588, they did not test positive for C. butyricum.
Use of CBM-588 was also associated with a higher objective response rate (58 vs 20%), as well as significantly longer progression-free survival (median 55.0 vs 10.7 weeks) and a trend toward better overall survival (median unreached in both arms).
Rates of grade 3 and more severe adverse events were “comparable” in the two arms, although the presenter cautioned that one patient given CBM-588 developed grade 4 neutropenia.
“Limitations of this study include the small size” and that it was conducted at a single site, Meza said, adding that the “results are nonetheless intriguing and warrant further exploration.”
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