Guselkumab demonstrates long-term efficacy and maintenance of treatment response postwithdrawal in systemic treatment-naïve patients and nonresponders to fumaric acid esters: results from parts II and III of a randomized active-comparator-controlled phase IIIb trial (POLARIS).

BACKGROUND: The anti-interleukin-23 antibody guselkumab (GUS) demonstrated favourable week 24 efficacy and safety over fumaric acid esters (FAE) in systemic treatment-naïve patients with moderate-to-severe plaque psoriasis (study part I). OBJECTIVES: To compare, in study part II, the sustainability of treatment responses (weeks 24-32) in GUS- and FAE-treated patients and treatment responses (weeks 32-56) in patients treated with GUS and FAE and in FAE nonresponders switching to GUS; and, in part III, to investigate the maintenance of response through week 100 in patients withdrawn from GUS at week 56. METHODS: At week 0, systemic treatment-naïve patients were randomized 1 : 1 to GUS or FAE as per label. At week 32, patients with a Psoriasis Area and Severity Index (PASI) 75 (≥ 75% improvement in PASI score) response (r) continued assigned treatment (GUSr-GUS; FAEr-FAE), whereas nonresponders (nr) received GUS (FAEnr-GUS; GUSnr-GUS). GUS-treated patients with a week 56 PASI 90 response (≥ 90% improvement in PASI score) were withdrawn (w) and followed until loss of response or week 100. RESULTS: At week 32, 98% (n = 54/55) of GUS- and 41% (n = 14/34) of FAE-treated patients were PASI 75 responders. At week 56, 91%, 50% and 80% of GUSr-GUS, FAEr-FAE and FAEnr-GUS patients, respectively, achieved a PASI 90 response; 72%, 29% and 45%, respectively, achieved a Dermatology Life Quality Index score of 0/1. At week 100, 44 weeks postwithdrawal, 47% (n = 17/36) and 25% (n = 3/12) of GUS-GUSw and FAE-GUSw patients, respectively, maintained a PASI score ≤ 5. Overall, the adverse event and discontinuation rates were lower for GUS than FAE. CONCLUSIONS: In these exploratory analyses, GUS, as a first-line systemic treatment or second-line systemic treatment in FAE nonresponders, was associated with long-term clinical efficacy up to week 100, including a withdrawal period.

Starvation-induced degradation of yeast hexose transporter Hxt7p is dependent on endocytosis, autophagy and the terminal sequences of the permease.

The yeast high-affinity glucose transporters Hxt6p and Hxt7p are rapidly degraded during nitrogen starvation in the presence of high concentrations of fermentable carbon sources. Our results suggest that degradation is mainly due to the stimulation of general protein turnover and not caused by a mechanism specifically triggered by glucose. Analysis of Hxt6p/7p stability and cellular distribution in end4, aut2 and apg1 mutants indicates that Hxt7p is internalized by endocytosis, and autophagy is involved in the final delivery of Hxt7p to the vacuole for proteolytic degradation. Internalization and degradation of Hxt7p were blocked after truncation of its N-terminal hydrophilic domain. Nevertheless, this fully functional and stabilized hexose transporter could not maintain fermentation capacity of the yeast cells under starvation conditions, indicating a regulatory constraint on glucose uptake.

Characterisation of mammalian GLUT glucose transporters in a heterologous yeast expression system.

We have developed a new heterologous expression system for mammalian glucose transporters. The system is based on a Saccharomyces cerevisiae strain completely deleted for all its endogenous hexose transporters and unable to take up and to grow on hexoses. To target the heterologous glucose transporters into the yeast plasma membrane in a fully active form, additional mutations had to be introduced into the hexose transport-deficient strain. Although GLUT1 was localized at the cell surface already in the parent strain, it supported uptake of glucose only in an deltaHXT FGY1-1 mutant strain. Moreover, various mutations within the first half of the second predicted transmembrane helix converted GLUT1 into a form able to support uptake of glucose into yeast cells. GLUT4 was trapped in intracellular structures but became functionally expressed in the plasma membrane in deltaHXT FGY1-1 FGY4X mutant strains. Glucose transport kinetics were determined with intact yeast cells by zero-trans influx measurements with a Km of 3.2 mM for human GLUT1 and of 12.6 mM for human GLUT4. Cytochalasin B inhibited these activities. Growth tests revealed that both transporter proteins are able to mediate uptake of glucose, mannose and galactose, but not of fructose. The new heterologous expression system should be a valuable tool to develop cell based high-throughput screening assays for identifying pharmaceutical compounds influencing the transporters.