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Systemic sclerosis (SSc) is a heterogeneous autoimmune disease associated with several anti-nuclear antibodies (ANA), including those in the classification criteria , anti-RNA Pol III]. However, the presence of less common antibodies such as anti-fibrillarin (U3-RNP), that generate a clumpy nucleolar pattern by HEp-2 indirect immunofluorescence assay (IFA, ICAP AC-9), are considered disease specific and are with clinical subsets of SSc, therefore playing a role in diagnosis and prognosis. A specific and sensitive anti-fibrillarin assay would be an important addition to serological diagnosis and evaluation of SSc. The goal of this study was to evaluate a new particle-based multi-analyte technology (PMAT) for the measurement of anti-fibrillarin antibodies Methods:A total of 149 patient samples were collected including 47 samples from France (Lyon and Paris, n=32) and Italy (Careggi Hospital, Florence, n=15) selected based on AC-9 HEp-2 IFA staining (>1:640, clumpy nucleolar pattern) and 102 non-SSc controls [inflammatory bowel disease (IBD) n=20, Sjögren's syndrome (SjS) n=20, infectious disease (ID) n=7, systemic lupus erythematosus (SLE) n=17, rheumatoid arthritis (RA) n=17, and healthy individuals (HI) n=21]. All samples were tested on the anti-fibrillarin PMAT assay (research use only, Inova Diagnostics, USA). Additionally, the 47 anti-fibrillarin positive samples were also tested on PMAT assays for detecting other autoantibodies in ANA-associated rheumatic diseases (AARD). Anti-fibrillarin antibody data performed by fluorescence enzyme immunoassay (FEIA, Thermo Fisher, Germany) was available for 34 samples. Results:The anti-fibrillarin PMAT assay was positive in 31/32 (96.9%, France) and 12/15 (80.0 %, Italy) of samples preselected based on the AC-9 IIF pattern. Collectively, the PMAT assay showed 91.5% [95% Confidence Interval (CI): 80.1-96.6%] sensitivity with 100.0% (95% CI: 96.4-100.0%) specificity in non-SSc controls. Strong agreement was found between PMAT and FEIA with 100.0% positive qualitative agreement (34/34) and quantitative agreement (Spearman's rho=0.89, 95% CI:0.77.9-0.95%, p<0.0001). Although most anti-fibrillarin positive samples were mono-specific (69.8%), some expressed additional antibodies (namely Scl-70, centromere, dsDNA, Ro52, Ro60, SS-B, Ribo-P, DFS70, and EJ). Conclusion:The new PMAT assay had high level of agreement to FEIA for the detection of anti-fibrillarin antibodies. Further studies are warranted to investigate the clinical associations and performance of the new method in combination with other critical markers in the SSc panel.

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Introduction: Epidermal growth receptor (EGFR) is the most expressed membrane oncogenic protein in human cancers. KRAS and BRAF mutations are significant drivers of resistance to EGFR-targeted therapies. Unlike other treatments, EGFR-targeting, CD3 bispecific T cell engagers (TCEs) can potentially retain activity against tumors bearing resistance mutations. However, cytokine release syndrome (CRS), on-target off-tumor toxicities, and poor pharmacokinetics (PK) properties present significant clinical limitations for these potent immunomodulators. To overcome these challenges, Janux has developed JANX008, an EGFR- and CD3-targeted tumor-activated T cell engager (TRACTr). JANX008 is a humanized tri-specific protein that contains EGFR- and CD3-binding domains, an albumin binding domain to extend circulating half-life, and two different peptide masks fused to the molecule through tumor protease cleavable linkers. One peptide mask inhibits EGFR engagement on target cells, and the other inhibits CD3 engagement on T cells. Once the cleavage sequences undergo proteolysis by tumor proteases, the EGFR and CD3 masks are released, and the resulting active molecule can bind EGFR and CD3 on target cells. Methods: Peptide masks against EGFR- and CD3-binding domains were identified via phage display. The efficiency of the masks was evaluated using human EGFR and CD3 ELISAs. JANX008-induced cleavage-dependent T cell killing was evaluated in human PBMC/tumor cell co-culture assays. Anti-tumor efficacy of JANX008 was tested in multiple preclinical models, including EGFR antibody-resistant KRAS- and PIK3CA-mutant mouse colon cancer model (HCT116) and a fully human primary colorectal cancer (CRC) tumoroid system. The pharmacokinetic and safety profile of JANX008 was evaluated in non-human primate studies. Results: JANX008 target engagement was cleavage-dependent where masking reduced EGFR and CD3 binding by &gt;300x and &gt;1,000x, respectively. JANX008 exhibited potent cleavage- and dose-dependent activity in multiple preclinical models, including EGFR antibody-resistant tumor and T cell co-culture assays, humanized mouse CRC model, and a human primary CRC tumoroids with an intact tumor microenvironment. JANX008 showed a significantly enhanced safety profile in NHPs compared to non-masked EGFR-TCE, including decreased CRS-associated cytokines and healthy tissue toxicities at high exposures. Clinical chemistry, hematology, and pathology measurements all supported No-Observed-Adverse-Effect-Level ≥ 0.6 mg/kg/dose. Finally, the cleavable albumin-binding domain extended the half-life of JANX008 to ~94h, relative to the ~1.3h half-life of non-masked TCE, supporting its weekly clinical dosing. Conclusions: Preclinical data demonstrate key characteristics of JANX008, including cleavage-dependent activity, half-life extended PK, the potential for superior safety, and manufacturability properties that could mitigate significant limitations of TCEs and support JANX008 clinical development. Citation Format: Thomas R DiRaimondo, Natalija Budimir, Lina Ma, Simon Shenhav, Vanessa Cicchini, Hu Wu, Renee Jocic, Fabrece Roup, Calvin Campbell, Carolina Caffaro, Hans Aerni, Ugur Eskiocak, Wayne Godfrey, Charles Winter, Marc Nasoff, Neil Gibson, David Campbell, shahram Salek-Ardakani. Preclinical activity and safety profile or JANX008, a novel EGFR-targeting tumor-activated T cell engager for treatment of solid tumors [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B04.