Efficacy and Safety of a Novel Broad-Spectrum Anti-MRSA Agent Levonadifloxacin Compared with Linezolid for Acute Bacterial Skin and Skin Structure Infections: A Phase 3, Openlabel, Randomized Study

BACKGROUND

Levonadifloxacin is a novel broad-spectrum anti-MRSA agents belonging to the benzoquinolizine subclass of quinolone. It is developed for oral or intravenous administration for the treatment of infections caused by Gram-positive organisms including methicillin-resistant Staphylococcus aureus (MRSA).

OBJECTIVES

To establish the non-inferiority of levonadifloxacin compared with linezolid for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and to compare the safety of the two antimicrobials.

SUBJECTS AND METHODS

This was a Phase 3, multicentre, randomized, open-label, active- comparator study with 500 subjects. Oral levonadifloxacin 1000 mg was compared with oral linezolid 600 mg whereas IV levonadifloxacin 800mg was compared with IV linezolid 600 mg, each treatment was administered twice daily for 7-10 days. Non-inferiority was evaluated by comparing oral levonadifloxacin to oral linezolid and IV levonadifloxacin to IV linezolid for overall clinical response at TOC (Test of Cure) Visit.

RESULTS

The clinical cure rates observed at the TOC in the mITT (modified Intent to treat) populations for levonadifloxacin was numerically higher compared to linezolid in the IV sub-group [(91.0% verses 87.8%); treatment difference of 3.2% (95%CI, -4.5 to 10.9)] and in the oral sub-group (95.2% versus 93.6%); treatment difference of 1.6 % [95%CI, -4.2 to 7.3]). As the lowerbound of the 95% CI around the treatment difference was greater than -15% for both subgroups, the primary objective of the study was met. Therefore, both IV levonadifloxacin and oral levonadifloxacin were non-inferior to IV linezolid and oral linezolid, respectively. The majority of subjects in the micro-ITT population had a baseline infection caused by S. aureus with approximately 30% of subjects having MRSA. Levonadifloxacin (IV and oral) had a higher clinical cure rate at TOC for MRSA patients compared with linezolid (IV and oral), (95.0% vs. 89.3% respectively). Levonadifloxacin showed evidence of favourable clinical and microbiological efficacy in subjects with concurrent bacteraemia as well as in subjects with diabetes including diabetic foot infections caused by Gram-positive pathogens including MRSA. Pharmacokinetic analysis showed that bioavailability of oral levonadifloxacin was 90% and similar pharmacokinetic profile of levonadifloxacin by both routes provide an option for IV to oral switch for the treatment of subjects. Incidences of treatment-emergent adverse events (TEAEs) were similar between treatment groups and between IV (20.8% vs. 22.4%, for levonadifloxacin and linezolid, respectively) and oral therapy (16.0% vs. 13.5%, respectively), There were no SAEs or deaths related to study drug and the majority of the AEs observed were mild in nature. Overall, the administration of both IV and oral levonadifloxacin was well-tolerated in subjects with ABSSSI.

CONCLUSIONS

The results demonstrate that IV and oral levonadifloxacin therapy has excellent clinical activity against MRSA and offers advantage compared to other quinolones which generally lack MRSA coverage. Levonadifloxacin is safe and well tolerated in the treatment of ABSSSI caused by Gram -positive pathogens including MRSA as well as non-inferior to IV and oral linezolid, respectively. Similar pharmacokinetic profile of IV and oral levonadifloxacin provides an option for IV to oral switch for the treatment of subjects. Both oral and IV levonadifloxacin have recently been granted approval in India for the treatment of ABSSSI including diabetic foot infections and concurrent bacteraemia in adults (18 years of age or older). ClinicalTrials.gov Registration: NCT03405064. CTRI No.: CTRI/2017/06/008843.

Leaf biochemical adjustments in two Mediterranean resprouter species facing enhanced UV levels and reduced water availability before and after aerial biomass removal

Effects of supplemented UV radiation and diminished water supply on the leaf concentrations of phenols and antioxidants of two Mediterranean resprouter species, Arbutus unedo and Quercus suber, were assessed before and after entire aerial biomass removal. Potted seedlings of both species were grown outdoors for 8 months with enhanced UV-A + UV-B, enhanced UV-A or ambient UV, in combination with two watering conditions (field capacity or watering reduction). After this period, all aerial biomass was removed and new shoots (resprouts) developed for a further 8 months under the two treatments. In general, the investment in leaf phenols was substantially greater in A. unedo than in Q. suber, while Q. suber allocated more resources to non-phenolic antioxidants (ascorbate and glutathione). In response to enhanced UV-B radiation, Q. suber leaves rose their UV-screening capacity mainly via accumulation of kaempferols, accompanied by an increased concentration of rutins, being these effects exacerbated under low-watering conditions. Conversely, A. unedo leaves responded to UV-B radiation reinforcing the antioxidant machinery by increasing the overall amount of flavonols (especially quercetins) in seedlings, and of ascorbate and glutathione, along with catalase activity, in resprouts. Nevertheless, UV effects on the amount/activity of non-phenolic antioxidants of A. unedo resprouts were modulated by water supply. Indeed, the highest concentration of glutathione was found under the combination of enhanced UV-B radiation and reduced watering, suggesting an enlargement of the antioxidant response in A. unedo resprouts. Different biochemical responses to enhanced UV and drier conditions in seedlings and resprouts of these two species might modulate their competitive interactions in the near future.

Altitudinal and seasonal changes of phenolic compounds in Buxus sempervirens leaves and cuticles

The variation in the leaf content of phenolic compounds has been related to the UV-B changes of the environment in which plants grow. In this context, we aimed to investigate: a) whether the seasonal and altitudinal changes in the content of phenolic compounds of Buxus sempervirens L. leaves and cuticles could be related to the natural fluctuations in UV-B levels and b) the possible use of specific phenolic compounds as biomarkers of ambient UV-B levels. To achieve these goals we sampled, every three months during one year, leaves of B. sempervirens along an altitudinal gradient. At the lowest and the highest altitudes, we also conducted a UV-exclusion experiment to discern whether the observed changes could be attributed to the natural variation in UV-B. Results show that total phenolic content of leaves was lower in June than in the other sampling dates, which suggests a leaf ontogenic rather than a UV-B effect on the leaf content of these compounds. Regarding the elevational gradient, the overall amount of phenolic acids and neolignan of entire leaves increased with altitude while the total amount of flavonoids in leaf cuticles decreased. However, the lack of a significant effect of our UV-exclusion treatment on the content of these compounds suggests that the observed variations along the altitudinal gradient would respond to other factors rather than to UV-B. Concomitantly, we did not find any phenolic compound in leaves or cuticles of B. sempervirens that could be considered as a biomarker of ambient UV-B levels.

Carbon and nitrogen cycles in European ecosystems respond differently to global warming

The global climate is predicted to become significantly warmer over the next century. This will affect ecosystem processes and the functioning of semi natural and natural ecosystems in many parts of the world. However, as various ecosystem processes may be affected to a different extent, balances between different ecosystem processes as well as between different ecosystems may shift and lead to major unpredicted changes. In this study four European shrubland ecosystems along a north-south temperature gradient were experimentally warmed by a novel nighttime warming technique. Biogeochemical cycling of both carbon and nitrogen was affected at the colder sites with increased carbon uptake for plant growth as well as increased carbon loss through soil respiration. Carbon uptake by plant growth was more sensitive to warming than expected from the temperature response across the sites while carbon loss through soil respiration reacted to warming in agreement with the overall Q10 and response functions to temperature across the sites. Opposite to carbon, the nitrogen mineralization was relatively insensitive to the temperature increase and was mainly affected by changes in soil moisture. The results suggest that C and N cycles respond asymmetrically to warming, which may lead to progressive nitrogen limitation and thereby acclimation in plant production. This further suggests that in many temperate zones nitrogen deposition has to be accounted for, not only with respect to the impact on water quality through increased nitrogen leaching where N deposition is high, but also in predictions of carbon sequestration in terrestrial ecosystems under future climatic conditions. Finally the results indicate that on the short term the above-ground processes are more sensitive to temperature changes than the below ground processes.

A biomechanical study of the long bones in platyrrhines

The long bones of 72 individuals of extant platyrrhines, belonging to 17 species (11 genera) were studied by regressions of length, diameters and curvature. Cross-sectional shapes at midshaft and axial and bending strength indicators were also calculated. Results show that forelimb bones scale faster than hindlimb bones, for both length and diameters. Curvature scales faster in the femur than in other bones. Strength indicators showed a high variability in the relative importance of axial and bending loadings. Results are consistent with field observations of locomotor behaviour, mainly as regards quadrupedalism versus suspensory locomotion.

Photosynthesis and photoprotection in Quercus ilex resprouts after fire

Plants that resprout after fires often have higher rates of photosynthesis than before a fire. To elucidate the mechanism of this response, we studied gas exchange and chlorophyll fluorescence in Quercus ilex L. plants growing on control (unburned) sites and on sites that had been burned the preceding summer. In early July, photosynthetic rates and stomatal conductance were similar in plants on unburned and burned plots, and in young and old foliage within unburned plots. At this time, photochemical efficiency of photosystem II (PSII), nonphotochemical quenching of chlorophyll fluorescence (NPQ), and the de-epoxidation of violaxanthin to zeaxanthin were also similar among leaves of different ages and treatments. In late July, photosynthetic rates and stomatal conductances were much greater in resprouts on the burned areas than in unburned plants. From early to late July, unburned plants showed an increase in NPQ and the de-epoxidation of violaxanthin to zeaxanthin, indicating increased photoprotection as a result of enhanced nonradiative dissipation of excess light energy. Plants on the burned plots did not show these changes. Leaves of all ages and treatments showed no substantial reduction in potential quantum yield of PSII (F(v)/F(m)) at midday or predawn, indicating that there was little or no photoinhibition. Leaf nitrogen and soluble protein contents varied with leaf age during July, but did not vary between treatments. We conclude that the primary effect of burning is an increase in water availability to resprouting plants that eliminates the need for photoprotection, at least in the short term. The decrease in photosynthetic rates of unburned leaves in late July was the result of reduced stomatal conductance. We suggest that lowered stomatal conductance is the primary limiting factor in Q. ilex leaves, governing the regulation of carboxylation activity and energy dissipation processes.