Purpose: The gut microbiota is subject to multiple insults in allogeneic hematopoietic cell transplantation (allo-HCT) recipients. We hypothesized that preparative conditioning regimens contribute to microbiota perturbation in allo-HCT. Experimental Design: This was a retrospective study that evaluated the relationship between conditioning regimens exposure in 1,188 allo-HCT recipients and the gut microbiome. Stool samples collected from 20 days before transplantation up to 30 days after were profiled using 16S rRNA sequencing. Microbiota injury was quantified by changes in α-diversity. Results: We identified distinct patterns of microbiota injury that varied by conditioning regimen. Diversity loss was graded into three levels of conditioning-associated microbiota injury (CMBI) in a multivariable model that included antibiotic exposures. High-intensity regimens, such as total body irradiation (TBI)–thiotepa-cyclophosphamide, were associated with the greatest injury (CMBI III). In contrast, the nonmyeloablative regimen fludarabine–cyclophosphamide with low-dose TBI (Flu/Cy/TBI200) had a low-grade injury (CMBI I). The risk of acute GVHD correlated with CMBI degree. Pretransplant microbial compositions were best preserved with Flu/Cy/TBI200, whereas other regimens were associated with loss of commensal bacteria and expansion of Enterococcus. Conclusions: Our findings support an interaction between conditioning at the regimen level and the extent of microbiota injury.

Bortezomib was the first proteasome inhibitor (PI) discovered and demonstrated great efficacy in myeloma, both in vitro and in patients. However, still many patients ultimately relapse and there is the need for novel therapies. A second generation of PI have been discovered, potentially more effective ands some also orally administered. Carfilzomib is an irreversible proteasome inhibitor that showed great efficacy in clinical studies. Ixazomib is an oral compound that has been introduced recently in the therapeutic spectrum. Novel agents such as Marizomib seem promising in the fact that can also pass through the blood brain barrier and maybe effective also in CNS muyeloma. This review focus on all proteasome inhibitors available in clinics and the new ones coming soon.

Intestinal microbiota composition is implicated in several diseases; understanding the factors that influence it are key to elucidating host-commensal interactions and to designing microbiome-targeted therapies. We quantified how diet influences microbiome dynamics in hospitalized patients. We recorded 9,419 meals consumed by 173 patients undergoing hematopoietic cell transplantation and profiled the microbiome in 1,009 longitudinally collected stool samples from 158 of them. Caloric intake was correlated with fecal microbiota diversity. Bayesian inference revealed associations between intake of sweets or sugars during antibiotic exposure with microbiome disruption, as assessed by low diversity or expansion of the pathobiont Enterococcus. We validated this observation experimentally, finding that sucrose exacerbated antibiotic-induced Enterococcus expansion in mice. Taken together, our results suggest that avoiding sugar-rich foods during antibiotic treatment may reduce microbiome injury.

Diet shapes the composition of the gut microbiota¹; however, the specific effects of distinct food groups on microbiome dynamics are unclear, particularly in circumstances of extreme perturbation. Here we evaluated the relationship between diet and intestinal microbiome dynamics by precisely tracking 9,419 meals consumed by 173 patients who were hospitalized for haematopoietic cell transplantation and analysing subsequent microbiome changes. Bayesian inference applied to data from 158 patients with paired longitudinal microbiome samples revealed that the intake of sweets and sugars during antibiotic exposure predicted exacerbated microbial dysbiosis, manifesting as lowered α-diversity and greater expansion of the pathobiont Enterococcus. Experiments in mice also showed that sucrose supplementation increased and prolonged antibiotic-induced Enterococcus expansion. These data suggest that avoiding a diet rich in simple sugars during antibiotic treatment may mitigate microbiota disruption. Further studies in independent cohorts will offer opportunities to generalize these findings and evaluate microbiota-sparing interventions.