Objective. Prediction of relapses inConclusion. Serial measurement of ANCA levels is valuable for the early prediction of relapses in patients with WG.

No abstract

The presence of antineutrophil cytoplasmic autoantibodies with specificity for proteinase 3 (PR3-ANCA) usually is detected by enzyme-linked immunosorbent assay (ELISA) with purified PR3 as a substrate. We studied the technical performance of direct and capture ELISA using a recombinant proteolytically inactive form of PR3 produced in the baculovirus expression system for the detection of PR3-ANCA in 114 patients with systemic vasculitis at diagnosis. We found that ELISA using recombinant PR3 produced in insect cells is a promising alternative for ELISA with native PR3. We found a correlation between tests using recombinant or native PR3, as well as correlation of the ELISA results with ANCA titers measured by the indirect immunofluorescence technique. However, the specificity for ANCA-associated vasculitis of ELISA with recombinant PR3 was lower than ELISA using native PR3. Compared with the direct assay, capture ELISA is a more sensitive method for PR3-ANCA detection, with both native and recombinant PR3, and its results depend on the monoclonal antibody used to capture the antigen.

It is increasingly understood that cancers can be recognized by the immune system and inflammation relates to response. Combining stereotactic radiotherapy (SBRT), to increase release of cancer cell antigens, with an anti-CTLA-4 and PD-L1 inhibitor may lead to increased response rates. No solid biomarker in predicting treatment response is available. We set out to study feasibility of combined durvalumab (anti-PD-L1) and tremelimumab (anti-CTLA-4) with SBRT on the primary tumor. The extend of tumor-infiltrating cells has shown to correlate to improved prognosis using checkpoint inhibitor (CPI) treatment of various cancers. We hypothesized that the peripheral blood T-cell activation status may be a predictor of response, progression free survival (PFS) and overall survival (OS). Methods: Three immunotherapy regimes were combined with SBRT in sequential cohorts as ≥2nd line in CPI naïve patients with NSCLC stage IIIB/IV. One week after the 1st dose of CPI, patients were irradiated on the primary tumor (1x 20Gy on 9cc). The 1st cohort (n=3) received durvalumab, the 2nd and 3rd cohort (both n=6) a combination of durvalumab and tremelimumab, followed by durvalumab monotherapy. Exploratory endpoint was the correlation of response with T-cell function. T-cell function was assessed using flow cytometric analysis of peripheral blood T-cells and compared to simultaneously included healthy controls. In short, whole blood was activated ex vivo using Staphylococcal enterotoxin B (SEB) after which the T-cell activation status was assesses by expression of CD69 and cytokines (IL-2, IFN-γ, TNF-α). Patients were divided in above (responders, R) and below median PFS (non-responders, NR). We compared intracellular cytokine production in both CD4+ and CD8+ T-lymphocytes between both groups and with healthy controls (HC) using the Mann-Whitney U test. Findings: Fifteen patients were included as described above. Median PFS was 2 months, OS 10 months (immature). Baseline characteristics of both groups were comparable. T-cell function was assessed in 14 patients and HC at baseline. Data are shown as median (P-value) for R vs NR below. R had a significant higher percentage activated CD8+ T-cells upon SEB stimulation than NR: CD8+CD69+ 15.8 vs 3.5 (0.008) and IL-2+CD8+CD69+ 8.8 vs 2.9 (0.02). There was a trend in TNF-α+CD8+CD69+ 19.8 vs 8.0 (0.11) and IFN-ɣ+CD8+CD69+ 21.4 vs 5.5 (0.22). These differences were all significant for R compared to HC (p<0.03), but not for NR (P>0.66). Interpretation: With a mild antigen independent stimulus (SEB), the CD8+ T-cells of responders were significantly more activated at baseline compared to non-responders and healthy controls. This suggests an elevated pre-treatment T-cell activation status in patients that responded to the treatment and the possibility to use this as a potential biomarker to predict the response to CPI treatment. Disclosure: This study was sponsored by a research grant from AstraZeneca. Citation Format: Hanneke Kievit, M. Benthe Muntinghe-Wagenaar, Lucie B.M. Hijmering-Kappelle, Birgitta I. Hiddinga, J Fred Ubbels, Robin Wijsman, Bart-Jan Kroesen, Marcel J. van der Leij, A. Rutgers, Harry J. Groen, Huib A. Kerstjens, Anthonie J. van de Wekken, T Jeroen Hiltermann. Baseline T-cell function predicts response to SBRT and immunotherapy in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1984.