Efficacy and safety of vixotrigine in idiopathic or diabetes-associated painful small fibre neuropathy (CONVEY): a phase 2 placebo-controlled enriched-enrolment randomised withdrawal study.

Background: No pharmacological treatments are specifically indicated for painful small fibre neuropathy (SFN). CONVEY, a phase 2 enriched-enrolment study, evaluated the efficacy and safety of vixotrigine, a voltage- and use-dependent sodium channel blocker, in participants with idiopathic or diabetes-associated painful SFN. Methods: CONVEY was a phase 2, multicentre, placebo-controlled, double-blind (DB), enriched-enrolment, randomised withdrawal study. The study was conducted at 68 sites in 13 countries (Europe and Canada) between May 17, 2018, and April 12, 2021. Following a 4-week open-label period in which 265 adults with painful SFN (a mixture of large and small fibre neuropathy was not exclusionary) received oral vixotrigine 350 mg twice daily (BID), 123 participants (with a ≥30% reduction from baseline in average daily pain [ADP] score during the open-label period) were randomised 1:1:1 to receive 200 mg BID, 350 mg BID or placebo for a 12-week double-blind (DB) period. Primary endpoint was change from baseline in ADP at DB Week 12. Secondary endpoints included the proportion of participants with a ≥30% reduction from baseline in ADP and the proportion of Patient Global Impression of Pain (PGIC) responders at DB Week 12. Treatment-emergent adverse events (AEs) were monitored. Statistical significance was set at 0.10 (2-sided). The trial was registered on ClinicalTrials.gov (NCT03339336) and on ClinicalTrialsregister.eu (2017-000991-27). Findings: A statistically significant difference from placebo in least squares mean reduction in ADP score from baseline to DB Week 12 was observed with vixotrigine 200 mg BID (-0.85; SE, 0.43; 95% CI, -1.71 to 0.00; p = 0.050) but not 350 mg BID (-0.17; SE, 0.43; 95% CI, -1.01 to 0.68; p = 0.70). Numerically, but not statistically significantly, more participants who received vixotrigine vs placebo experienced a ≥30% ADP reduction from baseline (68.3-72.5% vs 52.5%), and only the 350 mg BID group had significantly more PGIC responders vs placebo (48.8% vs 30.0%; odds ratio = 2.60; 95% CI, 0.97-6.99; p = 0.058) at DB Week 12. AEs were mostly mild to moderate in the vixotrigine groups. The most common AEs (≥5% of vixotrigine-treated participants) in the DB 200 mg BID and 350 mg BID vixotrigine groups were falls, nasopharyngitis, muscle spasm, and urinary tract infection. Interpretation: In our study, vixotrigine 200 mg BID, but not 350 mg BID, met the primary endpoint; more vixotrigine-treated participants experienced a ≥30% reduction from baseline in ADP at DB Week 12. Vixotrigine (at both dosages) was well tolerated in participants with SFN. Funding: Biogen, Inc.

Effect of Moxifloxacin plus Pretomanid against Mycobacterium tuberculosis in Log Phase, Acid Phase, and Nonreplicating-Persister Phase in an In Vitro Assay.

Combination therapy is a successful approach to treat tuberculosis in patients with susceptible strains of Mycobacterium tuberculosis However, the emergence of resistant strains requires identification of new, effective therapies. Pretomanid (PA824) and moxifloxacin (MXF) are promising options currently under evaluation in clinical trials for the treatment of susceptible and resistant mycobacteria. We applied our recently described screening strategy to characterize the interaction between PA824 and MXF toward the killing of M. tuberculosis in logarithmic growth phase (log phase), acid phase, and nonreplicating-persister (NRP) phase. Respective in vitro data generated for the H37Rv and 18b strains were evaluated in a microdilution plate system containing both drugs in combination. The Universal Response Surface Approach model from Greco et al. (W. R. Greco, G. Bravo, and J. C. Parsons, Pharmacol Rev 47:331-385, 1995) was used to characterize the nature of the interaction between both drugs; synergistic or additive combinations would prompt additional evaluation in the hollow-fiber infection model (HFIM) and in animal studies. The interaction between MXF and PA824 was additive against M. tuberculosis organisms in acid phase (interaction parameter [α] = 5.56e-8 [95% confidence interval {CI} = -0.278 to 0.278] and α = 0.408 [95% CI = 0.105 to 0.711], respectively), NRP phase (α = 0.625 [95% CI = -0.556 to 1.81] and α = 2.92 [95% CI = 0.215 to 5.63], respectively), and log phase (α = 1.57e-6 [95% CI = -0.930 to 0.930] and α = 1.83e-6 [95% CI = -0.929 and 0.929], respectively), prompting further testing of this promising combination for the treatment of tuberculosis in the HFIM and in animal studies.

Effect of Linezolid plus Bedaquiline against Mycobacterium tuberculosis in Log Phase, Acid Phase, and Nonreplicating-Persister Phase in an In Vitro Assay.

Tuberculosis is the ninth-leading cause of death worldwide. Treatment success is approximately 80% for susceptible strains and decreases to 30% for extensively resistant strains. Shortening the therapy duration for Mycobacterium tuberculosis is a major goal, which can be attained with the use of combination therapy. However, the identification of the most promising combination is a challenge given the quantity of older and newer agents available. Our objective was to identify promising 2-drug combinations using an in vitro strategy to ultimately be tested in an in vitro hollow fiber infection model (HFIM) and in animal models. We studied the effect of the combination of linezolid (LZD) and bedaquiline (BDQ) on M. tuberculosis strain H37Rv in log- and acid-phase growth and M. tuberculosis strain 18b in log- and nonreplicating-persister-phase growth in a plate system containing a 9-by-8 matrix of concentrations of both drugs alone and in combinations. A characterization of the interaction as antagonistic, additive, or synergistic was performed using the Greco universal response surface approach (URSA) model. Our results indicate that the interaction between LZD and BDQ is additive for bacterial killing in both strains for both of the metabolic states tested. This prescreen strategy was suitable to identify LZD and BDQ as a promising combination to be further tested in the HFIM. The presence of nonoverlapping mechanisms of drug action suggests each drug in the combination will likely be effective in suppressing the emergence of resistance by M. tuberculosis to the companion drug, which holds promise in improving treatment outcomes for tuberculosis.

Identification of optimal parameter combinations for the emergence of bistability.

Bistability underlies cellular memory and maintains alternative differentiation states. Bistability can emerge only if its parameter range is either physically realizable or can be enlarged to become realizable. We derived a general rule and showed that the bistable range of a reaction parameter is maximized by a pair of other parameters in any gene regulatory network provided they satisfy a general condition. The resulting analytical expressions revealed whether or not such reaction pairs are present in prototypical positive feedback loops. They are absent from the feedback loop enclosed by protein dimers but present in both the toggle-switch and the feedback circuit inhibited by sequestration. Sequestration can generate bistability even at narrow feedback expression range at which cooperative binding fails to do so, provided inhibition is set to an optimal value. These results help to design bistable circuits and cellular reprogramming and reveal whether bistability is possible in gene networks in the range of realistic parameter values.