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Background: Advanced cutaneous T-cell lymphomas (CTCLs) remain an unmet medical need. Brentuximab vedotin (BV), an anti-CD30 antibody-drug conjugate (ADC) linked to monomethyl auristatin E (MMAE), do not deliver significant long-term improvements in patient outcomes. More recently, mogamulizumab and anti-KIR3DL2 provided encouraging results but new targeted therapies are needed. Inducible Co-Stimulator (ICOS), a T-cell costimulatory receptor involved in the development of CTCLs, arouses interest. Methods: We used immunohistochemistry to study ICOS expression in skin biopsies of 23 patients with early-stage mycosis fungoides (MF), 12 with transformed MF (TMF) and 17 with Sézary Syndrome (SS), at diagnosis or in relapse. Skin samples from 12 patients with B-cell lymphomas, 14 with CD30 + lymphoproliferative disease (LPD), 12 with primary cutaneous CD4+ small/medium T-cell lympho-proliferative disorder and 13 with angioimmunoblastic T-cell lymphoma (AITL) were used as controls. ICOS expression by circulating Sézary cells and regulatory T cells (Tregs) in patients with SS was evaluated using flow cytometry and compared to healthy donors (HD) lymphocytes. In 5 patients with SS, we also analyzed concomitant biopsies from involved nodes. Then, we investigated the efficacy of anti-ICOS ADCs generated by coupling murine anti-ICOS 314.8 monoclonal antibodies with MMAE and pyrrolobenzodiazepine (PBD), in comparison to BV. We used ICOS + CTCL cell lines (MyLa, MJ and HUT78), murine xenograft models with MyLa and ICOS + Patient Derived Xenografts (PDXs) from patients with SS and AITL. In order to identify the best anti-ICOS clone that we should develop for a clinical trial, we evaluated the affinity of the antibody on the receptor, the internalization capacity of the antibody using pHAb Reactive Dyes kit (Promega®), and the ability of the antibody to act as an ADC using a secondary conjugate (Mab-ZAP kit, Advanced Targeting Systems®). Results: ICOS was highly expressed by the cutaneous atypical lymphocytic infiltrates in respectively 61%, 75% and 88% of patients with early-stage MF, TMF and SS, such as in all the involved nodes. Double staining experiments which were performed in both skin and lymph node revealed that ICOS expression appears mainly restricted to neoplastic CD4 + T-cells, with rare ICOS +CD8 + T-cells in the tumor micro-environment. ICOS expression by circulating Sézary cells was strong: 69 ± 7.3% versus 38.8 ± 7.1% of non-tumoral CD4 + cells (p In CTCL cell lines, we observed a significant dose-dependent decrease in cell viability in the presence of anti-ICOS-MMAE (IC50 = 8.2ng/mL) and anti-ICOS-PBD (IC50 = 1.2ng/mL) ADCs. In a mouse xenograft model (MyLa), anti-ICOS-MMAE ADCs provided a longer overall survival (OS) than BV (HR=15.2; CI95%: 3.2-71.1; p Among 8 different anti-ICOS clones, clone 314.8 had the best affinity on MyLa and MJ cell lines. Clones 53.3, 293.1, 92.17, 88.2 and 279.1 also had good affinity to receptor, whereas clones 145.1 and 121.4 had poor affinity. Using the internalization pHAb reactive dyes kit, we found that clones 314.8, 53.3, 92.17, 88.2 internalized significantly better and faster than the other ones. In order to verify if there is a correlation between internalization capacity and ADC effect, clones 53.3, 92.17 and 145.1 were coupled to MMAE. While anti-ICOS-53.3 and anti-ICOS-92.17 ADCs had similar efficacy to anti-ICOS-314.8 ADCs on MyLa, anti-ICOS 145.1 ADCs resulted in significantly lower cell death. Finally, all clones showed good ability to act as ADCs with Mab-ZAP, excluding clones 279.1, 145.1 and 121.4. Discussion: ICOS is a promising therapeutic target because it is expressed both by tumor T-cells and regulatory T-cells. We report for the first time the strong and frequent expression of ICOS in CTCLs, as well as the preclinical efficacy of anti-ICOS ADCs on CTCL cell line and PDXs. These results could be extended to the spectrum of follicular variant peripheral T-cell lymphomas. Conclusion: Collectively, our findings provide the preliminary basis for a therapeutic trial Figure 1 Figure 1. Disclosures Lopez: Emergence Therapeutics: Current holder of individual stocks in a privately-held company. Bagot: Takeda: Membership on an entity's Board of Directors or advisory committees. Olive: ImCheck Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Emergence Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Alderaan Biotechnology: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees.

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Immune checkpoint inhibitors (ICI), most commonly anti-PD-1 (programmed cell death 1) and anti-PD-L1 (programmed cell death ligand 1) therapies, have revolutionized the treatment of many cancers. ICI may activate the immune system response even in healthy tissues, which can cause immune-related adverse events (irAEs).(1) Several cases of bullous pemphigoid (BP) triggered by anti-PD-1/PD-L1 therapy have been reported.

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The treatment of advanced-stage cutaneous T-cell lymphoma (CTCL) remains an unmet medical need. Mogamulizumab, anti-KIR3DL2, and brentuximab vedotin (BV), an anti-CD30 antibody–drug conjugate (ADC) coupled with monomethyl-auristatin-E (MMAE), provided encouraging results, but new targeted therapies are needed. Inducible T-cell costimulator (ICOS), a T-cell costimulatory receptor, is a promising therapeutic target, not only because it is expressed by malignant T cells in CTCL but also because of its connection with the suppressive activity of regulatory T (Treg) cells. Immunohistochemical analysis revealed that ICOS was widely expressed by malignant cells in skin biopsy specimens from 52 patients with mycosis fungoides and Sézary syndrome (SS), as well as in involved node biopsy specimens from patients with SS. Furthermore, flow cytometry demonstrated its strong expression by circulating tumor cells in all our patients with SS. Percentages of ICOS+ Treg cells were significantly higher in patients with SS than in healthy donors. We then investigated the preclinical efficacy of anti-ICOS ADCs generated by coupling murine anti-ICOS monoclonal antibodies with MMAE and pyrrolobenzodiazepine. In 3 CTCL cell lines (Myla, MJ, and HUT78), we observed a significant dose-dependent decrease in cell viability in the presence of anti-ICOS ADCs. In addition, anti-ICOS-MMAE ADCs had an in vitro and in vivo efficacy superior to BV in a mouse xenograft model (MyLa). Finally, we assessed the efficacy of anti-ICOS ADCs in ICOS+ patient-derived xenografts from patients with SS and angioimmunoblastic T-cell lymphoma. Collectively, our findings provide the preliminary basis for a therapeutic trial.

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A Nodular Pink Lesion with an Uncommon Diagnosis: A QuizMost melanomas are diagnosed by the patients themselves or by their partners or relatives; they alone can describe its history. We designed a prospective cross-sectional study to describe patients' perception of morphology, growth pattern and kinetics of their primary melanoma over 1 mm in thickness before resection. Patients were interviewed with a questionnaire, a grid representing 9 possible scenarios of melanoma growth, and a set of 87 photographs of potential aspects of melanomas and precursors. Most patients were able to describe the growth of their melanoma and select pictures representative of its successive aspects before resection. Among 453 patients, 60% reported a preexisting lesion present for years. Growth pattern scenarios concurred with tumor kinetics but with no statistical difference between nodular and superficial spreading subtypes. These subjective patient-reported indicators about melanoma growth over time could dynamically complement its objective pathological analysis otherwise static at a single time point.

International audience; Introduction: The promotion of antitumor response by targeting co-stimulatory B7 superfamily members has become evident to create a new wave of cancer immunotherapy. Inducible Co-Stimulator (ICOS), which is expressed on activated T cells, gained interest in the translational medicine community.Areas covered: We performed an extensive literature review using the keywords 'ICOS' and 'cancer', and the Clinicaltrials.gov database for early phase clinical trials targeting ICOS. In this review, we highlight the dual role of ICOS in oncogenesis in different malignancies. We summarize the current state of knowledge about ICOS/ICOSL pathway targeting by immunotherapies.Expert opinion: Due to its multifaceted link with anti-tumor immunity, both antagonist and agonist antibodies might be of interest to target the ICOS/ICOSL pathway for tumor treatment. Indeed, ICOS activation might potentiate the effect of an inhibitory checkpoint blockade, while its neutralization could decrease the function of immunosuppressive Tregs and inhibit lymphoid tumor cells expressing Tfh markers.

Background Primary cutaneous lymphomas (PCLs) are a heterogeneous group of T-cell (CTCL) and B-cell (CBCL) malignancies. Little is known about their epidemiology at initial presentation in Europe and about potential changes over time. Objectives The aim of this retrospective study was to analyse the frequency of PCLs in the French Cutaneous Lymphoma Registry (GFELC) and to describe the demography of patients. Methods Patients with a centrally validated diagnosis of primary PCL, diagnosed between 2005 and 2019, were included. Results The calculated incidence was unprecedently high at 1·06 per 100 000 person-years. The number of included patients increased yearly. Most PCL subtypes were more frequent in male patients, diagnosed at a median age of 60 years. The relative frequency of rare CTCL remained stable, the proportion of classical mycosis fungoides (MF) decreased, and the frequency of its variants (e.g. folliculotropic MF) increased. Similar patterns were observed for CBCL; for example, the proportion of marginal-zone CBCL increased over time. Conclusions Changes in PCL frequencies may be explained by the emergence of new diagnostic criteria and better description of the entities in the most recent PCL classification. Moreover, we propose that an algorithm should be developed to confirm the diagnosis of PCL by central validation of the cases.

Background: In a previous study, we reported the strong expression of Inducible T-cell costimulatory (ICOS) by Sézary cells, and presented the excellent preclinical efficacy results of anti-ICOS antibody drug conjugates (ADCs) in both Sézary syndrome (SS) and angioimmunoblastic T-cell lymphoma. Although exerting a potent direct action on the tumor cell, ADCs have the disadvantage of being associated with a cumulative toxicity, related to the conjugated drug. The development of antibody-dependent cell-mediated cytotoxicity/phagocytosis (ADCC/ADCP)-inducing anti-ICOS monoclonal antibodies (mAbs) is therefore of great importance to ensure long-term maintenance therapy. Methods: We first determined which anti-ICOS clone was the best candidate to induce an ADCC effect on ICOS + cell lines (MyLa, MJ and HUT78), using Mouse FcγRIII ADCC Bioassay (Promega®). The selected mAb was then chimerized and afucosylated (GlymaxX® technology, Evitria®). Secondly, we evaluated in vitro ADCC and ADCP effect of the chimeric anti-ICOS mAb against ICOS + CTCL cell lines, compared to both positive controls (mogamulizumab (moga) and alemtuzumab) and negative controls (IgG1 isotype control, and rituximab). To perform ADCC experiments, we co-incubated target cells with mAbs and allogenic NK lymphocytes from healthy volunteers (HV). Cellular apoptosis was measured by flow cytometry using the Caspase 3/7 assay (Promega®). For ADCP, monocytes were sorted from HV blood samples and treated with M-CSF. Target cells were labeled with PKH67 (Sigma-Aldrich®) and after co-incubation, CD14 +CD11b +PKH67 + monocytes were analyzed by flow cytometry. Finally, we verified the ADCC/ADCP potency of anti-ICOS mAbs on primary Sézary cells isolated from 16 moga-naïve SS patients, and 6 patients who had developed resistance to moga. We also questioned whether anti-ICOS mAbs were able to promote the autologous apoptosis of Sézary cells and T regulatory cells (Tregs) when directly incubated with peripheral blood mononuclear cells (PBMCs) from patients with SS. Results: Among 7 different anti-ICOS clones, 314.8, 92.17 and 293.1 clones had the higher ADCC activity against MyLa, MJ and HUT78. Of these 3 clones, 314.8 had the best affinity to the receptor, and the best ability to inhibit binding between ICOS receptor and a recombinant ICOS ligand protein. Anti-ICOS 314.8 mAb was then chosen to be chimerized and glyco-engineered. ICOS and CCR4 were strong and similarly expressed on MyLa and MJ. HUT78 had only mild expression of ICOS and CD52. Anti-ICOS mediated potent ADCC of cell lines (respectively 39.1±5% and 52.6±2.4% for MyLa and MJ cells), without significant difference when compared to mogamulizumab. In HUT78 cells, anti-ICOS induced a specific apoptosis of 35.7±5% versus 15.6±5.6% with alemtuzumab (p=0.02; CI95%: 4.1-36.1). Moreover, phagocytosis induced by anti-ICOS was significantly increased than that induced by negative controls. On MyLa cells, anti-ICOS had a greater phagocytosis activity than moga (59.4±5.2% vs 39.4±5.1%, p=0.031). Expression of ICOS by circulating tumor cells was found in all the 16 moga-naïve patients. The expression was strong, as 61±6% of tumor cells expressed ICOS vs 20±8% of non-tumoral CD4 + cells. CCR4 was more expressed than ICOS on both Sézary cells and non-tumoral CD4 + cells (91±6%, and 44±9% respectively). Anti-ICOS induced the apoptosis of 57.1±4.7% Sézary cells, compared to 16.9±2.2% with rituximab (p Ex vivo, anti-ICOS allowed 39.4±19.9% and 70.1±20.1% lysis of Sézary cells and Tregs respectively, with no difference with moga and alemtuzumab. However, the depletion of non-tumoral CD4 + and total PBMCs was significantly lower with anti-ICOS mAbs than with moga and alemtuzumab. Discussion: In a recent study, we showed that Treg cells of patients with SS have a high expression of ICOS. Here, we demonstrate that anti-ICOS mAbs induce Tregs depletion, which may improve immune profiles and emphasize Sézary cells killing. Our data suggest robust anti-tumor activity of anti-ICOS mAbs in SS, and xenograft experiments are underway to confirm these findings. Disclosures Lopez: Emergence Therapeutics: Current holder of individual stocks in a privately-held company. Bagot: Takeda: Membership on an entity's Board of Directors or advisory committees. Olive: Alderaan Biotechnology: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; ImCheck Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Emergence Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees.

International audience; These guidelines were developed by the psoriasis research group of the French Society of Dermatology with the aim of providing updated decision-making algorithms for the systemic treatment of adult patients with moderate-to-severe psoriasis. Our algorithms were generated after rigorous evaluation of existing guidelines on the treatment of psoriasis and of publications concerning new systemic treatments, not yet incorporated into existing guidelines. A total of nine existing guidelines and 53 publications related to new systemic treatments were found to meet our criteria for use in the generation of the algorithms. We have proposed two new algorithms to assess therapeutic responses, both of which incorporate emerging criteria for evaluating treatment goals. Updated therapeutic strategy algorithms, incorporating both established and new systemic therapies, were also generated for the treatment of plaque psoriasis and psoriatic arthritis, together with recommendations for the treatment of particular forms of psoriasis and treatment of patients with comorbidities.

Background Few epidemiologic data are available regarding biologic liver abnormalities during psoriasis flares. Objectives The aim of this study was to assess the prevalence of biological liver test abnormalities (LTA) in a psoriasis population and the risk factors associated with LTA. Methods A retrospective cross-sectional study in four hospital dermatology tertiary care centres included patients admitted for severe psoriasis flare between 1st January 2010 and 31st December 2011. During the same period, a control population was selected comprising patients admitted for contact and/or atopic eczema. Data were collected on hospital records and biology software. LTA was defined as serum AST and/or ALT and/or ALP concentration above the upper normal limit (UNL) and/or GGT concentration above 2 UNL. Prevalence of LTA with 95% confidence intervals (95% CI) was compared between the psoriatic and control populations. Factors associated with LTA at P < 0.05 were considered for the final multivariate logistic regression model. Results Two hundred and forty psoriasis patients and 96 eczema control patients were included. One hundred and fifty-five(64.6%) of the psoriasis patients were male, aged 55 years on average (±17.6); 192 (80.0%) had plaque-type psoriasis (PV) and 52 (21.6%) had localized (n = 32) or generalized (n = 20) pustular psoriasis (PP). Prevalence of LTA was 36% (95% CI, 30–42) in the psoriatic population, significantly higher than in controls (17%, 95% CI 9.5–25). Risk factors independently associated with LTA comprised PV (OR 3.79; 95% CI 1.48–9.65), PP (OR 3.80; 95% CI 1.40–10.25) and previously diagnosed liver disease (underlying hepatic steatosis, viral hepatitis or excessive alcohol consumption) (OR 3.88; 95% CI 2.02–7.45). No association was found with systemic antipsoriatic drug therapies. Conclusion In severe psoriasis, liver impacting comorbidities and/or specific psoriatic inflammation, the latter mostly in PP cases, more than drug-related liver toxicity, appears to predominantly account for LTA. Clinicians should be aware of this, to avoid unjustified withdrawal of useful systemic drugs.

e20040 Background: Advanced stage cutaneous T-cell lymphomas (CTCLs) remain an unmet medical need. Immunomodulatory agents such as mogamulizumab, anti-KIR3DL2 and brentuximab vedotin (BV), an anti-CD30 antibody–drug conjugate (ADC) coupled to monomethyl-auristatin-E (MMAE), provided encouraging results but new targeted therapies are needed. Inducible Co-Stimulator (ICOS), a T-cell costimulatory receptor involved in the development of CTCLs, arouses interest. Methods: We used immunohistochemistry to study ICOS expression in skin biopsies of 23 patients with early-stage mycosis fungoides (MF), 12 with transformed MF (TMF) and 17 with Sézary Syndrome (SS), at diagnosis or in relapse. ICOS expression by circulating Sézary cells and regulatory T cells (Tregs) in patients with SS was evaluated using flow cytometry, and compared to healthy donors (HD) lymphocytes. In 5 patients with SS, we also analyzed concomitant biopsies from involved nodes. Then, we investigated the efficacy of anti-ICOS ADCs generated by coupling murine anti-ICOS monoclonal antibodies with MMAE, in comparison to BV. We used ICOS+ CTCL cell lines (MyLa and MJ), murine xenograft models with MyLa and ICOS+ Patient Derived Xenografts (PDXs) from patients with SS and angioimmunoblastic T-cell lymphoma (AITL). Results: ICOS was highly expressed by the cutaneous atypical lymphocytic infiltrates in respectively 61%, 75% and 88% of patients with early-stage MF, TMF and SS, such as in the 5 patients with node involvement. ICOS expression by circulating Sézary cells was strong: 69±7.3% versus 38.8±7.1% of non-tumoral CD4+ cells ( p< 0.009; CI95%: 8.7-51.6); and 31±3.2% of CD4+ cells in HD ( p< 0.0001; CI95%:20.3-46.3). Percentages of ICOS+ Tregs were significantly higher in patients with SS than in HD. In CTCL cell lines, we observed a significant dose-dependent decrease in cell viability in the presence of anti-ICOS ADCs. In a mouse xenograft model (MyLa), anti-ICOS ADCs provided a longer overall survival (OS) than BV (HR = 15.2;CI95%:3.2-71.1; p< 0.0006). Finally, in ICOS+ PDXs anti-ICOS ADCs significantly improved OS, and reduced the number of tumor cells in the blood, bone marrow and spleen. No evidence of ADC toxicity was observed in treated mice. Conclusions: All together our results show that ICOS is a therapeutic target of interest in CTCLs and provide the preliminary basis for a therapeutic trial

Background:In lung adenocarcinoma, molecular profiling of actionable genes has become essential to set up targeted therapies. However, the feasibility and the relevance of molecular profiling from the cerebrospinal fluid (CSF) in the context of meningeal metastasis have been poorly assessed.Methods:We selected patients with stage IV lung adenocarcinoma harbouring metastatic cells in the CSF after cytological analysis. Seven samples from six patients were eligible for molecular testing of epidermal growth factor receptor (EGFR), V-Ki-ras2 Kirsten rat sarcoma viral oncogene homologue (KRAS), v-Raf murine sarcoma viral oncogene homologue B1 (BRAF) and human epidermal growth factor receptor 2 (HER2) mutations using quantitative polymerase chain reaction (PCR) high-resolution melting curve analysis and Sanger sequencing after DNA extraction from the cell pellets of the CSF.Results:Five patients showed mutations in one or two actionable genes, two harboured anEGFRmutation (exons 19 and 21), one only aKRASmutation, one bothEGFRandKRASmutations and one aBRAFmutation. In all cases, the results of mutation testing provided new major information for patient management, leading to therapeutic adaptation. CSF molecular analysis identified mutations not detected in other neoplastic sites for two patients. In one case, the EGFR p.Thr790Met was identified. CSF was also the only sample available for genetic testing for almost all patients at the time of disease progression.Conclusions:When cancer cells are present in the CSF, the molecular profiling from the cell pellets is relevant, as it can detect supplemental or different mutations compared to a previous analysis of the primitive tumour or plasma cell-free DNA and allows the adaptation of the treatment strategy.

The recent success of checkpoint-inhibitors in cancer treatment paved the way for the development of new strategies of agonist and antagonist agents against B7 superfamily members. Inducible Co-Stimulator (ICOS), a co-stimulatory receptor for T-cell enhancement, arouses interest. Areas covered: We performed an extensive literature search with PUBMED using the keywords 'ICOS' and 'cancer' to discuss its involvement in oncogenesis, its expression in different malignancies, and its targeting in relevant preclinical studies. We also searched the Clinicaltrials.gov database for recent updates on early phase clinical trials. Expert opinion: ICOS/ICOSL axis has a dual effect and might participate in anti-tumour T cell response as well as a pro-tumour response due to its connection with regulatory T-cells (Tregs) suppressive activity. Therefore, both antagonist and agonist antibodies might be of interest in the targeting ICOS/ICOSL pathway for cancer treatment. In preclinical studies, ICOS agonist monoclonal antibodies (mAbs) have shown to potentiate the effect of inhibitory checkpoint blockade. In contrast, antagonistic anti-ICOS mAbs could not only inhibit lymphoid tumour cells expressing ICOS, but also dampen immunosuppressive Tregs. Two agonist and one antagonist mAbs are evaluated in phase I/II trials. Efficacy, safety, and combination strategies with anti-ICOS agonist or antagonist have yet to be specified.

International audience; BACKGROUND: TNF weakly inducer of apoptosis (TWEAK) is member of the TNF ligand superfamily. Various data support that TWEAK produced by synovial macrophages may contribute to synovitis observed in psoriatic arthritis (PsoA). In PsoA, anti-TNF therapy has been successful in agreement with the key role of TNF in the pathogenesis and the generation by PsoA patients of anti-TNF autoantibodies referred as "beneficial autoimmunity to pro-inflammatory mediators". However, the role of TNF-alpha in the regulation of TWEAK modulation of inflammation during PsoA remains unknown. METHODS: We have studied level course during anti-TNF therapy of serum soluble TWEAK. In the same cohort, we have investigated the generation of TWEAK-binding autoantibodies by PsoA patients before and after anti-TNF therapy. RESULTS: Patients with PsoA had significantly higher serum levels of TWEAK compared with controls [respective means (±SEM) were 645 pg/ml (64) and 467 pg/ml (23); (p = 0.006)] but serum soluble TWEAK levels were not correlated with BASDAI (Spearman's coefficients \textless0.003, p \textgreater 0.05). Our study showed that soluble TWEAK levels were not modulated by etanercept therapy [respective Means (±SEM) were 605 (95) (week 12) and 744 (97) (week 24) pg/ml; (p \textgreater 0.23)]. Anti-TWEAK autoantibodies were detected in 9/13 (69.2 %) PsoA patients at inclusion and only in 3/57 (5.3 %) healthy blood donors (p \textless 0.0001). These circulating antibodies were persistent in PsoA patients and detected at similar levels during etanercept therapy. Moreover we showed that they had a down regulating effect on CCL-2 secretion by endothelial cells stimulated by rh TWEAK in vitro. CONCLUSION: Our study revealed that during psoriatic arthritis (1) serum TWEAK was up regulated and (2) TWEAK-binding autoantibodies are generated. Both parameters were not influenced by anti-TNF therapy and persisted at high levels during anti-TNF therapy. For the first time we described here TWEAK-binding IgG autoantibodies with a down regulating effect on CCL-2 secretion by endothelial cells stimulated by rh TWEAK in vitro. Finally, our results suggest that TWEAK may be involved in PsoA pathogeny. Trial registration This clinical trial was approved by the local Ethics Committee "Comité de Protection des Personnes Sud-Méditerranée V" with the registration number: 2011-002954-29, and French health minister registration number AFSSAPS A110784-42 obtained the 08/22/2011. This clinical trial is registered in Clinical trial.gov under the number: NCT02164214.

9552 Background: Anti-PD1 are now pivotal in the treatment of metastatic melanoma (MM). Some concerns have emerged regarding the risk/benefit ratio of their combination with stereotactic radiosurgery. Methods: Retrospective assessment of the interaction between Gamma-Knife radiosurgery (GKRS) and anti-PD1 in terms of toxicity and OS in mm patients (pts) with BM. Patients were included if they were under anti-PD1 (PRE) at time of GKRS, or if they had started anti-PD1 concomitantly with GKRS (CO), or had received anti-PD1 within 3 months after GKRS (POST). Results: Among 47 pts who received GKRS and anti-PD1 during their disease course, 35 fulfilled PRE or CO or POST criteria (anti PD1 1st line therapy in 10 pts and 2d or more in 25 pts). One pt died before radiological evaluation. GKRS targeted a single BM in 10 pts and multiple BMs in 24 (max 19 BMs). Out of the 128 BMs treated, 6 cases of increase of preexisting edema (4.7%) and 8 hemorrhages (6.25%) occurred in 12 pts, but only 5 events (5%) were regarded as Adverse Radiation effects (ARE), being symptomatic in 3 pts (8% of pts). One BM had to be resected because of the occurrence of a symptomatic hemorrhage with hemiparesis 9 month after treatment. Median follow- up from GKRS was 13.7 mths. Median overall survival (OS) from GKRS and 1st BM were 14.8 and 26.5 mths respectively, with 6 and 12 mths 0S rates from GKRS of 65.7% and 57%, respectively. Local failure was observed in 5 pt. Median time to new BM was 12.6 mths. There was no significant difference in outcomes in pts, depending on PRE, CO and POST conditions. Conclusions: In this series, the largest to date of pts with BMs treated by GKRS and anti-PD1,ARE were within the expected range and survival rates appear promising. Given the natural propensity of MM-BMs for bleeding and edema our data do not support an increased risk with the combination of GKRS and anti-PD1. Regarding the timing between anti-PD1 administration and GKRS our data do not support a higher efficacy or higher toxicity among the 3 following potential mechanisms: immuno- sensitization to radiation (PRE), immuno-radio direct synergy (CO) or radiosensitization to immunotherapy (POST).