PRECISION MEDICINE IN PSORIASIS: GENETIC INFLUENCE ON RESPONSIVENESS TO ANTI-ILs THERAPIES AND CLINICAL IMPLICATION OF PHARMACOLOGICAL TREATMENT WITH ANTI-TNF-alpha

Background: Psoriasis is a multifactorial disorder caused by inherited susceptibility alleles and environmental factors. In the current pathogenic mechanisms model, the cross-talk between autoreactive T-cells and resident keratinocytes plays a central role for the initiation and progression of disease. Early upstream events occurring in psoriasis include induction of innate immunity responses triggered by keratinocyte-derived autoantigens, which can activate dendritic cells (DC). DC, in turn, drive expansion of T lymphocytes, typically T helper 17 in the initial phase and IFN--producing T cells during the chronic phase of the disease, by releasing IL-23 and IL-12, respectively. T cells present in active psoriatic skin establish a cytokine milieu, responsible for the local aberrant inflammatory responses and the impaired differentiation and cornification processes in the epidermis. Genetic epidemiologic studies put in evidence that the disease inheritability is up to 60-90%, which is one of the major reported for multifactorial diseases. In support of this, studies carried out on genome-wide genotyping platforms have now identified 63 psoriasis susceptibility loci. Specific single-nucleotide polymorphisms (SNPs) were, thus, identified in genes involved in inflammatory pathways, epidermal differentiation functions, as well as in innate and adaptive immune responses. However, the major genetic determinant of psoriasis resides in PSORS1 locus, mapping to the MHC region on chromosome 6p21. This locus spans the MHC class I region and encompasses nine genes, including HLA-C, CDSN and CCHCR1, that are highly polymorphic. In particular, HLA-Cw6 allele is known as the strongest psoriasis susceptibility genetic factor and supposed to be involved in antigen presentation to CD8+ T cells. Immunomodulation with biologics targeting pathogenic molecules are highly effective in the treatment of psoriasis, as well as of various immune-mediated inflammatory diseases. Nowadays, a variety of biological therapies are available for psoriatic patients. These agents are potentially highly effective, and include the anti-TNF biologics, the anti-IL-12/23 inhibitor, the newer class of biologicals targeting IL-17 and its receptor, and the lastly identified anti-IL-23p19 drugs. These agents are potentially highly effective, even though they may differ in time until a clinically satisfactory response is reached. In addition, a variable percentage of patients does not or only partially respond to biological therapies or develops cutaneous reactions, namely paradoxical psoriasis, as side effects. These often requires the interruption of the imputable drug and switching to other therapies. Several evidences have related the mechanisms underlying drug response variability to the presence of specific genetic variants. To date, SNPs located in HLA-C, TNFAIP3, TNFA, TNFRSF1B, IL-12B and IL-23A genes have been associated to different response to anti-TNF and anti-IL-12/IL-23 drugs. Genetic factors have also been postulated to play a pivotal role in the development of paradoxical psoriasiform reactions to anti-TNFs. Research hypothesis and aims: Considering the variable response to biological drugs, the possible undesirable side-effects and, not least, the high cost of biological therapies, the identification of genetic biomarkers to predict treatment response of psoriatic patients to biological drugs, either in terms of efficacy/inefficacy or safety improvement of the drugs, could greatly impact clinical decisions. We hypothesize that the variability of response of psoriatic patients to biologics, in particular to anti-IL-17A or to anti-IL-12/IL-23 drugs, as well as of patients treated with TNF blockers and developing psoriasis-like paradoxical reactions, can be attributed to their genetic background. Therefore, the present research aimed at identifying: i) the genetic variants of psoriasis-related risk loci associating with clinical responsiveness to anti-IL17A or anti-IL12/IL-23 drugs in two large cohorts of patients affected by mild-to-severe plaque psoriasis; ii) the genetic variants or SNPs and the immunological profiles, associating with the development of paradoxical psoriasis in patients undergone anti-TNF therapy for hidradenitis suppurativa (HS) condition. Materials and Methods: A panel of SNPs associated with psoriasis-related risk loci were analyzed in two cohorts of patients diagnosed with moderate-to-severe chronic plaque-type psoriasis, treated with secukinumab (n = 63) or ustekinumab (n = 150). The severity of psoriasis and response to treatment were evaluated using the Psoriasis Area and Severity Index (PASI) score and then at follow-up visits on weeks 8, 16, 24, 40, 56, 64, 72, 88, 100 (secukinumab) or on weeks 4, 12, 28, 40, 52, 64, 76, 88, 100 (ustekinumab). The selected SNPoma, composed of n = 44 SNPs, highly represented in the psoriatic populations (minor allele frequency > 0.3) and potentially implicated in immune responses (T-cell signaling, antigen presentation), as well as inflammatory pathways and skin barrier function, were evaluated by a Next-Generation Sequencing (NGS) technology. Differences between the groups based on the clinical response to anti-ILs (≥ 75% reduction of PASI score, PASI75; ≥ 90% reduction of PASI, PASI90; 100% reduction of PASI, PASI100) were evaluated by statistical test and univariate logistic regression analysis. SNP analysis was also performed on three HS patients, who developed paradoxical psoriasis following adalimumab therapy for HS condition. Immunological profiles were examined by immunohistochemistry and real-time PCR in skin biopsies kept from paradoxical skin lesions, as well as by flow cytometry on blood and skin-derived T cells. The immunological patterns of paradoxical psoriasis were compared with those present in canonical psoriasis. Results: A panel of SNPs in HLA-C region were found to associate to a better response to secukinumab treatment. In particular, a significant association between four SNPs in HLA-C region, namely HLA-Cw6 v1 (classical HLA-Cw6), HLA-Cw6 v2, HLA-Cw6 v3, HLA-Cw6 LD, and response to the drug was found. Psoriatic patients carrying HLA-Cw6 v1 reached PASI100 faster than HLA-Cw6-neg patients, and maintained this result up to week 24. HLA-Cw6-pos patients also showed a tendency to greater respond to secukinumab, in terms of achievement of PASI90 and PASI100. However, the most significant associations were observed for HLA-Cw6 v2 and HLA-Cw6 LD variants, whose presence in psoriatic patients was associated to the achievements of PASI75 or PASI 90 starting from week 16 or week 4, respectively, up to week 56. Interestingly, the absence of HLA-Cw6 v3 allele in psoriatic population guaranteed a better response to secukinumab, in terms of achievement of PASI75 at different time-points of evaluation (weeks 24, 40, 56, 64, 72, 88, 100). Differently from secukinumab-treated patients, ustekinumab-treated cohort was strongly influenced by HLA-Cw6 v1 allele status, but not by HLA-Cw6 LD, HLA-Cw6 v2, or HLA-Cw6 v3 variants. The association between HLA-Cw6 v1 allele presence and response to ustekinumab was significant for patients reaching PASI90 or PASI100, starting from week 12 up to week 100. In addition, two SNPs in TNFA gene determined a greater and long-lasting response to ustekinumab. Similarly, the presence or absence of two SNPs in CDSN gene, respectively, strongly associated with a good response to ustekinumab (PASI90), which was maintained up to 100 weeks. PASI90 was also reached by the majority of ustekinumab-treated patients carrying SNP in CCHCR1 gene. The SNP analysis of the three HS patients with paradoxical reactions showed that they carried out allelic variants in genes predisposing to psoriasis. Among them, SNPs in ERAP1, NFKBIZ and TNFAIP genes and in the HLA-C genomic region were found. Moreover, paradoxical psoriasiform skin reactions showed immunological features common to acute psoriasis, characterized by cellular players of innate immunity. In addition, type I IFNs typical of acute psoriasis were highly expressed in paradoxical skin reactions, concomitantly to other innate immunity molecules, such as the catheledicin LL37 and lymphotoxin (LT)- and LT-Differently from classical psoriasis, psoriasiform lesions of HS patients showed a reduced number of IFN- and TNF--releasing T lymphocytes. On the contrary, IL-22 immunoreactivity significantly augmented together with the IL-36 staining. Implication of the study /Conclusions: SNPs in HLA-C region, including HLA-Cw6 psoriasis allele, and in CDSN, CCHCR1 and TNFA genes, all mapping in PSORS1 locus, were found to associate to a better response to secukinumab or to ustekinumab treatments in two large cohorts of psoriatic patients. Thus, determination of these SNP status could be useful to predict the clinical response to secukinumab or ustekinumab therapies. The present research also identified a panel of allelic variants present in HLA-C region, as well as in ERAP1, NFKBIZ and TNFAIP3 genes in three patients showing paradoxical psoriasis reactions after anti-TNF- therapy. Investigations on the immunological profiles of patients with paradoxical psoriasis permitted to unveil new pathogenic mechanisms involving innate immunity pathways, and in common with acute psoriasis. As a whole, these data are potentially of great interest since very few studies investigated the association between polymorphisms and paradoxical psoriasis. In the future, it will be necessary to extend the analysis of SNPs predisposing to psoriasis in larger cohorts of patients manifesting paradoxical skin reactions to anti-TNF drugs, but also in a population successfully responding to anti-TNF treatment to identify possible difference in the genetic background of the patients. Considering the increased incidence of paradoxical psoriasiform reactions, it becomes increasingly necessary to investigate the immunological and genetic profiles of patients developing these reactions, in order to understand the pathogenic mechanisms and to predict the risk of developing paradoxical effects.