Linewidth of single photon transitions in Mn12_{12}-acetate

We use time-domain terahertz spectroscopy to measure the position and linewidth of single photon transitions in Mn$_{12}$-acetate. This linewidth is compared to the linewidth measured in tunneling experiments. We conclude that local magnetic fields (due to dipole or hyperfine interactions) cannot be responsible for the observed linewidth, and suggest that the linewidth is due to variations in the anisotropy constants for different clusters. We also calculate a lower limit on the dipole field distribution that would be expected due to random orientations of clusters and find that collective effects must narrow this distribution in tunneling measurements.Comment: 5 pages, accepted to Physical Review

Baseline Levels of Circulating Inflammatory Biomarkers Stratify Patients with Vitiligo Who Significantly Repigment after Treatment with Ruxolitinib Cream

Background: Efficacy of ruxolitinib cream, a topical Jak1/Jak2 inhibitor, was demonstrated in a phase 2 trial in patients with vitiligo. Objective: This study aimed to characterize circulating inflammatory biomarker profiles in patients who demonstrated ≥50% improvement in facial Vitiligo Area Scoring Index scores by week 24 (group 1) and those who did not (group 2). Design: This was a posthoc analysis of a multicenter, randomized, double-blind, vehicle-controlled, phase 2 study in which screening was conducted between June 7, 2017 and March 21, 2018. Population: Patients aged between 18 and 75 years with vitiligo, including depigmentation affecting ≥0.5% of body surface area on the face and ≥3% of body surface area on nonfacial areas, were eligible. Intervention: Patients applied 1.5% ruxolitinib cream to lesions once or twice daily for 52 weeks. Main outcomes and measures: Patients were grouped by achievement of ≥50% improvement in facial Vitiligo Area Scoring Index at week 24. Proteomic analysis was performed on baseline serum samples. Results: Mean ± standard error facial Vitiligo Area Scoring Index in group 1 (n = 30) versus group 2 (n = 27) improved by 79.9 ± 4.0% versus 1.1 ± 7.3% and 91.9 ± 1.5% versus 25.1 ± 13.4% at weeks 24 and 52, respectively. Broad proteomic analysis revealed 76 proteins (of 1,104 tested) that were differentially expressed between groups 1 and 2 at baseline (P < 0.05). Ten distinct proteins were upregulated in group 1; 64 were elevated in group 2. Conclusion: This analysis identified potential differences between patients who achieved ≥50% improvement in facial Vitiligo Area Scoring Index at 24 weeks and those who did not that require deeper scientific interrogation and may be important in stratifying therapeutic benefit for patients with vitiligo. Trial Registration: The original study was registered at ClinicalTrials.gov, NCT03099304

27568 Maintenance of repigmentation after discontinuation of ruxolitinib cream in patients with vitiligo

Treatment with ruxolitinib cream (Janus kinase [JAK] 1/JAK2 inhibitor) in adult patients with vitiligo resulted in substantial repigmentation over 52 weeks in a phase 2 dose-ranging study (NCT03099304). We assessed maintenance of repigmentation among responders from the phase 2 study following ruxolitinib discontinuation after 104 weeks of treatment. Patients initially randomized to ruxolitinib cream (1.5% twice daily [BID], 1.5% once daily [QD], 0.5% QD, or 0.15% QD) with evidence of facial repigmentation at Week 24 who completed ≥1 follow-up visit 1, 3, or 6 months after an additional 52 weeks of 1.5% ruxolitinib cream BID monotherapy (Weeks 52-104) were analyzed. Loss of repigmentation was defined as an increase in Vitiligo Area Severity Index score during the last follow-up visit vs Week 104 on ruxolitinib cream. Sixteen patients were included in the analysis (1.5% BID, n = 3; 1.5% QD, n = 5; 0.5% QD, n = 3; 0.15% QD, n = 5 [including 2 patients rerandomized to 1.5% BID/0.5% QD after Week 24]). Four patients (25.0%; 1.5% QD, n = 1; 0.5% QD, n = 1; 0.15% QD, n = 2) had repigmentation loss over 1-6 months of follow-up; no patients from the 1.5% ruxolitinib BID treatment group (with 2 years’ exposure) experienced repigmentation loss. There were no significant differences in baseline serum levels of chemokine (C-X-C motif) ligand (CXCL) 9, CXCL10, or interleukin-15 in patients who experienced loss vs maintenance of repigmentation after ruxolitinib cream discontinuation. This exploratory analysis suggests that repigmentation with ruxolitinib cream monotherapy may be maintained postdiscontinuation; larger follow-up studies are required to confirm these findings