Citations

SummaryThe oral proteasome inhibitor ixazomib is approved in the United States, European Union and other countries, in combination with oral lenalidomide and dexamethasone (Rd), for the treatment of patients with multiple myeloma who have received at least one prior therapy. Approval was based on the global, randomised, double‐blind, placebo‐controlled Phase III TOURMALINE‐MM1 study of ixazomib‐Rd (IRd) versus placebo‐Rd in patients with relapsed/refractory multiple myeloma. IRd resulted in a significant improvement in progression‐free survival versus placebo‐Rd (median: 20·6 vs. 14·7 months; hazard ratio 0·74). Common toxicities observed more commonly with IRd versus placebo‐Rd were thrombocytopenia, nausea, vomiting, diarrhoea, constipation, rash, peripheral neuropathy, peripheral oedema and back pain; these were generally grade 1/2 in severity except for thrombocytopenia (19% vs. 9% grade 3/4), which appeared manageable and reversible, with no differences between arms in significant bleeding or dose discontinuations. No cumulative toxicities were observed, indicating the potential feasibility of long‐term IRd treatment. Safety data from TOURMALINE‐MM1 are reviewed and guidance for managing clinically relevant adverse events associated with IRd is provided. Most toxicities were manageable with supportive care and dose delays or reductions as needed. Clinicians should be aware of and understand these potential side effects to optimise and prolong patient benefit.

Serotonin [5-hydroxytryptamine (5-HT)], an important neurotransmitter and a paracrine messenger in the gastrointestinal tract, regulates intestinal secretion by its action primarily on 5-HT3and 5-HT4receptors. Recent studies highlight the role of gut microbiota in 5-HT biosynthesis. In this study, we determine whether human-derived gut microbiota affects host secretory response to 5-HT and 5-HT receptor expression. We used proximal colonic mucosa-submucosa preparation from age-matched Swiss Webster germ-free (GF) and humanized (HM; ex-GF colonized with human gut microbiota) mice. 5-HT evoked a significantly greater increase in short-circuit current (Δ Isc) in GF compared with HM mice. Additionally, 5-HT3receptor mRNA and protein expression was significantly higher in GF compared with HM mice. Ondansetron, a 5-HT3receptor antagonist, inhibited 5-HT-evoked Δ Iscin GF mice but not in HM mice. Furthermore, a 5-HT3receptor-selective agonist, 2-methyl-5-hydroxytryptamine hydrochloride, evoked a significantly higher Δ Iscin GF compared with HM mice. Immunohistochemistry in 5-HT3A-green fluorescent protein mice localized 5-HT3receptor expression to enterochromaffin cells in addition to nerve fibers. The significant difference in 5-HT-evoked Δ Iscbetween GF and HM mice persisted in the presence of tetrodotoxin (TTX) but was lost after ondansetron application in the presence of TTX. Application of acetate (10 mM) significantly lowered 5-HT3receptor mRNA in GF mouse colonoids. We conclude that host secretory response to 5-HT may be modulated by gut microbiota regulation of 5-HT3receptor expression via acetate production. Epithelial 5-HT3receptor may function as a mediator of gut microbiota-driven change in intestinal secretion.NEW & NOTEWORTHY We found that gut microbiota alters serotonin (5-HT)-evoked intestinal secretion in a 5-HT3receptor-dependent mechanism and gut microbiota metabolite acetate alters 5-HT3receptor expression in colonoids.View this article's corresponding video summary at https://www.youtube.com/watch?v=aOMYJMuLTcw&feature=youtu.be .

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal (GI) disorders. Despite its prevalence, the pathophysiology of IBS is not well understood although multiple peripheral and central factors are implicated. Recent studies suggest a role for alterations in gut microbiota in IBS. Significant advances in next-generation sequencing technology and bioinformatics and the declining cost have now allowed us to better investigate the role of gut microbiota in IBS. In the following review, we propose gut microbiota as a unifying factor in the pathophysiology of IBS. We first describe how gut microbiota can be influenced by factors predisposing individuals to IBS such as host genetics, stress, diet, antibiotics, and early life experiences. We then highlight the known effects of gut microbiota on mechanisms implicated in the pathophysiology of IBS including disrupted gut brain axis (GBA), visceral hypersensitivity (VH), altered GI motility, epithelial barrier dysfunction, and immune activation. While there are several gaps in the field that preclude us from connecting the dots to establish causation, we hope this overview will allow us to identify and fill in the voids.