Comparative efficacy and safety of ilunocitinib and oclacitinib for the control of pruritus and associated skin lesions in dogs with atopic dermatitis

Severity scales are used to grade skin lesions in clinical trials for treatment of dogs with atopic dermatitis (AD). At this time, only two scales have been validated, namely the Canine Atopic Dermatitis Extent and Severity Index (CADESI)-3 and the Canine Atopic Dermatitis Lesion Index (CADLI). However, the high number of assessed sites makes the CADESI-3 impractical. The aim of this study was to develop and validate a fourth version of the CADESI that is simpler and quicker to administer. Body sites, lesions and severity grades were revised by members of the International Committee on Allergic Diseases of Animals (ICADA). The newly designed CADESI-4 was tested for its validity (i.e. content, construct and criterion), reliability (i.e. inter- and intra-observer reliability and internal consistency), responsiveness (i.e. sensitivity to change) and time to administer. Disease severity benchmarks were chosen using receiver operating characteristic methodology. The CADESI-4 was simplified in comparison to its previous version to comprise 20 body sites typically affected in atopic dogs. Three lesions (erythema, lichenification and alopecia/excoriation) were scored from 0 to 3 at each site. The CADESI-4 had satisfactory validity, reliability and sensitivity to change. On average, the time to administer a CADESI-4 was one-third that of a CADESI-3. Proposed benchmarks for mild, moderate and severe AD skin lesions are 10, 35 and 60, respectively. The CADESI-4 is simpler to use and quicker to administer than its previous version. The ICADA recommends the CADESI-4 instead of the CADESI-3 to score skin lesions of AD in dogs enrolled in clinical trials.

Clinical trials enrolling dogs with atopic dermatitis (AD) use validated instruments that aggregate the extent and severity of selected skin lesions; none of these provides a global assessment of the severity of all lesions. To validate an Investigator Global Assessment (IGA) instrument to globally evaluate the severity of skin lesions in dogs with AD. Forty dogs with AD. A 2D graphic IGA (2D-IGA) instrument was created to subjectively score, with a single dot, the overall extent and severity of all canine AD lesions. This tool was tested for its validity (content, construct and criterion), reliability (inter- and intraobserver) and sensitivity to change. The content of the 2D-IGA was first validated by a supportive vote by the International Committee of Allergic Diseases of Animals (ICADA) membership. Its construct was verified by positive correlations between the 2D-IGA scores and those of the Canine Atopic Dermatitis Extent and Severity Index, 4th iteration (CADESI-04) and the Canine Atopic Dermatitis Lesion Index (CADLI) (Spearman's rank-order correlation, P<0.0001). The positive correlation (P<0.0001) between an Owner Global Assessment of Disease Severity (OGADS) and the 2D-IGA indirectly satisfied its criterion. Scores graded by the same investigator hours apart and those between investigators were positively correlated (P<0.0001), thereby validating this scale's intra- and interobserver reliabilities. Finally, the changes in 2D-IGA values during treatment were correlated positively with scores of an Owner Global Assessment of Treatment Efficacy (OGATE; P<0.0001), thus showing its sensitivity to change. This novel 2D-IGA is a simple static graphic instrument that could be useful for clinical trials testing the efficacy of interventions for canine AD.

Previous studies indicate that canine atopic dermatitis (AD) is associated with expression of the Th2 cytokine IL‐4, but that mRNA for the Th1 cytokines IFNγ, TNFα and IL‐2 is expressed in lesional atopic skin. This suggests that Th1 cytokines are involved in the pathogenesis of chronic lesional AD. The aim of this study was to determine whether the expression of Th1 cytokine mRNA correlates with the clinical severity of canine AD. Samples were taken from 23 atopic and 12 healthy dogs. Atopic dermatitis was diagnosed on accepted clinical criteria and exclusion of other pruritic dermatoses. The healthy dogs had no history or clinical signs of any skin disease or condition likely to affect immune function. The clinical severity was scored using a modified canine atopic dermatitis extent and severity index (CADESI). Six‐millimetre punch biopsies of nonlesional skin were collected from both healthy and atopic dogs. Lesional skin was taken from areas of erythematous macular papular dermatitis avoiding sites of secondary infection. Gene transcripts for the housekeeping gene gluteraldehyde‐3‐phosphate dehydrogenase (GAPDH), IFNγ, TNFα, IL‐2 and IL‐4 were amplified by RT‐PCR. Forward and reverse primers were designed from published canine sequences. Specificity was confirmed by southern blotting and hybridization to internal sequence probes. The PCR products were run on 1.2% polyacrylamide‐ethidium bromide gels and imaged under 590 nm ultraviolet light. Levels of mRNA in each sample were expressed as (cytokine net band intensity)/(GAPDH net band intensity) using Kodak 1D software. Duplicate biopsies for histopathology were fixed in 10% neutral buffered formalin, paraffin embedded, sectioned and stained with H&amp;E. Five ×400 images of the superficial interfollicular dermis were captured for quantitative analysis. The degree of cell infiltration was assessed by calculating the proportion of the image area that consisted of cell nuclei using Object‐Image software. Spearman's nonparametric correlation was used to test the data. There were significant correlations between cellular infiltration and mRNA levels for IFNγ (P &lt; 0.0001, n = 13), TNFα (P = 0.046, n = 8) and IL‐2 (P = 0.023, n = 12) in lesional skin. No such correlation was seen in either nonlesional (n = 23) or healthy skin (n = 12). There were no significant correlations between cellular infiltration and IL‐4 mRNA levels in lesional (n = 8), nonlesional (n = 23) and healthy skin (n = 10). There were significant correlations between the CADESI scores and mRNA levels for IFNγ (P = 0.02, n = 13), TNFα (P = 0.04, n = 8) and IL‐2 (P = 0.008, n = 12) in lesional skin, but not in nonlesional skin (n = 23). There was no correlation between CADESI scores and IL‐4 mRNA levels in either lesional (n = 8) or nonlesional skin (n = 23). This suggests that Th1 cytokines are pivotal in the pathogenesis of chronic lesional AD. In contrast, IL‐4 does not appear to be linked to the development of chronic lesions. These findings support the hypothesis of a switch from Th2 to Th1 polarisation in the pathogenesis of canine AD. Funding: The Wellcome Trust.

To estimate the extent and severity of atopic dermatitis (AD)-related skin lesions, clinical trials enrolling dogs with AD often use categorical scales such as the Canine Atopic Dermatitis Extent and Severity Index, 4th iteration (CADESI-04) and Canine Atopic Dermatitis Lesion Index (CADLI). Despite recent progress in the standardization of these AD-grading scales, the evaluation of the severity of skin lesions (including erythema) remains subjective. To validate an optical set-up with a smartphone and a dermatoscope for the objective estimation of skin erythema severity in atopic dogs. Forty-three dogs with AD. An erythema index (EI) was calculated from calibrated skin images and compared to the dermatologist's erythema severity estimate using the erythema grading scale used in the CADESI-04, as well as an ad hoc Visual Analog Scale (VAS) with a continuous palette of red shades. We found a strong correlation based on the Spearman rank correlation coefficient between all erythema valuations: CADESI-04 and VAS: 0.93 [95% CI: (0.85, 0.96)]; CADESI-04 and EI: 0.85 (0.72, 0.92); VAS and EI: 0.82 (0.67, 0.91). There was a good agreement between the objective EI and CADESI-04-based estimates because 71% of samples were classified in the same erythema severity category. When comparing the EI and the VAS, the standard deviation of misestimates was 12% (maximum 100%). The proposed optical set-up has the potential to make erythema severity estimation objective, thus leading to more reliable AD severity scales for the use in experimental canine AD models or in clinical trials enrolling atopic dogs.

096 Transcriptomic analysis of epidermal barrier molecules, cytokines and growth factors in atopic dermatitis lesions

In this pilot study, we wished to determine if C-reactive protein (CRP) levels could be a useful severity or treatment biomarker for canine atopic dermatitis (AD). Nine atopic dogs received allergen immunotherapy for 1 year. Blood was collected before and at four re-evaluation visits. At each time point, the skin lesions were graded with the Canine Atopic Dermatitis Extent and Severity Index (CADESI) 4, and the plasma CRP levels were measured by Enzyme-linked Immunosorbent Assay (ELISA). We found a significant yet minimal correlation between the CRP levels and the CADESI4 scores. The CRP levels were not significantly different between dogs with AD of increasing severity. Finally, there was no correlation between the percentage change in CADESI4 and CRP values during immunotherapy. In conclusion, the lack of significant difference in CRP levels between dogs of increasing AD severity and lack of correlation between percentage changes in skin lesion and CRP values suggest that this protein would not be a clinically-useful biomarker in atopic dogs.

095 Koebnerisin (S100A15) signals via mTOR in keratinocytes to control epidermal maturation in psoriasis

Canine atopic dermatitis (cAD) is a common, chronic skin condition characterised by epidermal barrier dysfunction, immune dysregulation and cutaneous dysbiosis. While 'emollient plus' formulations are widely used in human atopic dermatitis (hAD), their role in cAD remains underexplored. To evaluate the clinical efficacy and owner-perceived value of a novel emollient plus formulation as a co-adjuvant treatment for cAD. Twenty-one client-owned dogs with controlled, nonseasonal cAD completed the study. A proof-of-concept, bench-to-bedside study was conducted over 30 days. Dogs received a once-daily application of a novel emollient plus formulation developed in-house. Clinical outcomes were assessed using pruritus Visual Analog Scale (pVAS)10 and Canine Atopic Dermatitis Extent and Severity Index (CADESI)-04 scores, alongside skin barrier function parameters (trans epidermal water loss [TEWL] and pH) at the pinnae and inguinal areas. Owners evaluated therapeutic efficacy via the Owner Global Assessment of Treatment Efficacy (OGATE) questionnaire and sensorial acceptability through a survey. Significant reductions were observed in pVAS10 (4.25 ± 1.85 to 3.38 ± 1.79; p = 0.016) and CADESI-04 (24.62 ± 18.48 to 13.43 ± 7.44; p = 0.02) scores. TEWL (18.63 ± 17.33 to 9.56 ± 10.75; p = 0.049) and pH (6.07 ± 0.97 to 5.41 ± 0.71; p = 0.01) only had significant reductions at the pinnae. Owner satisfaction was exceptionally high, with 90.47% rating treatment efficacy as 'good to excellent'. The sensorial properties of the formulation also received consistently positive ratings. This cAD-targeted emollient product demonstrated promising efficacy in reducing pruritus and skin lesions while possibly improving skin barrier function. Its favourable safety profile and high owner satisfaction suggest strong potential for routine clinical use in the management of cAD. Further controlled studies are warranted to confirm efficacy and optimised treatment protocols.

Gene expression in canine atopic dermatitis and correlation with clinical severity scores

The third iteration of the Canine Atopic Dermatitis Extent and Severity Index (CADESI-03) is the only tool rigorously validated for canine atopic dermatitis (CAD) lesion scoring. The CADESI-03 requires 248 evaluations, limiting its widespread use. The goal of the study was to develop and validate a practical method of grading CAD lesions that requires scoring only the frequently affected body regions. Fifty-seven privately owned atopic dogs were used in the study. The Canine Atopic Dermatitis Lesion Index (CADLI) was evaluated in an open, multicentre reliability study. Validity was assessed with expert opinion (content validity) and comparison of CADLI with existing disease severity measures (construct and criterion validity). Reliability was evaluated by analysing repeated observations of each dog. Convenience was assessed in terms of the time required to complete the scale. The CADLI scores correlated with overall assessment scores (r = 0.60, P < 0.001, linear mixed model) and pruritus severity scores (r = 0.53, P < 0.001, linear mixed model), establishing construct validity. The CADLI was strongly correlated with CADESI-03 (r = 0.84, P < 0.001, linear mixed model), establishing criterion validity. The CADLI values obtained by two observers correlated very strongly (r = 0.91, P < 0.001), as did the repeat values for the same observer (r = 0.98, P < 0.001). The mean time to complete the CADLI was less than that required for CADESI-03 (1.9 and 12.6 min, respectively), a highly significant difference (P < 0.001). The CADLI was found to be an effective measure of CAD lesion severity, strongly correlating with CADESI-03. The convenience of CADLI makes it suitable for use in both clinical research and practice.

Canine atopic dermatitis (AD) is a common skin disease with a 10–15 per cent prevalence. Current treatments vary in their efficacy and safety. The immunomodulatory properties of mesenchymal stem cells...

Bacterial infections and atopic dermatitis.

Vascular endothelial growth factor (VEGF) is a cytokine involved primarily in angiogenesis. In human atopic dermatitis (AD), VEGF has been detected in the stratum corneum and blood. To evaluate VEGF-A expression in the serum and stratum corneum of healthy and atopic dogs, and its possible correlation with disease severity in atopic dogs. Fifteen atopic and 15 healthy, privately owned dogs. The severity of clinical signs associated with AD was evaluated with the Canine Atopic Dermatitis Extent and Severity Index (CADESI-04). For all dogs, a single blood sample was performed and serum collected. Tape stripping (15 times) was performed on the left periocular area (lesional skin). A commercially available canine-specific VEGF-A enzyme-linked immunosorbent assay was performed with all samples. Vascular endothelial growth factor-A was undetectable in the serum. In the stratum corneum, there was no significant difference in VEGF-A concentrations between healthy (mean 89.4 ± 59.5 pg/ml) and atopic dogs (mean 100.3 ± 77.1pg/ml) (P=0.71). There was no correlation between stratum corneum VEGF-A concentrations and CADESI-04 scores. The role of VEGF in canine AD is unclear. Because of many variants, VEGF-C and VEGF-D or VEGF-A isotopes should be explored in the skin to better evaluate the role of VEGF in canine atopy. Full-thickness skin biopsy, molecular biology and histopathological investigation may be necessary to further assess cutaneous VEGF expression.

Studies on serum interleukin (IL)-31 levels in dogs with atopic dermatitis (AD) and their correlation with disease severity are limited. To the author's knowledge, there are no studies that measured serum IL-31 in dogs treated with lokivetmab injections, a selective inhibitor of this key cytokine in pruritus. The aim of the study was to evaluate serum IL-31 levels in dogs treated with lokivetmab and correlate it with the severity of canine atopic dermatitis using the pruritus visual analog scale (pVAS) and canine atopic dermatitis extent and severity index (CADESI-04). Ten client-owned dogs diagnosed with AD received two injections of lokivetmab four weeks apart. Disease severity was assessed using the pVAS and CADESI-04 scores before and after both injections. In addition, canine serum IL-31 levels were measured at the same moments. Serum IL-31 was detected in all dogs in the study. There was a significant reduction in pVAS scores and serum IL-31 after administrations. However, there was no difference in CADESI-04 scores, and there was no significant correlation between CADESI-04 scores and serum IL-31 in dogs diagnosed with AD. Nonetheless, a significant positive correlation was observed between the pVAS scores and serum IL-31 levels with lokivetmab therapy, which reinforces the role of IL-31 in the pathogenesis of pruritus in dogs with AD. The data presented here provide further evidence that IL-31 is directly involved in pruritus pathogenesis in dogs with AD. In addition, blocking IL-31 has a significant antipruritic effect, but has no influence on skin lesion severity and extension.

LB967 Effects of a topical atopic dermatitis lotion on the skin microbiome and associations with skin barrier and itch