ARGX-117, a therapeutic complement inhibiting antibody targeting C2.

BACKGROUND: Activation of the classical and lectin pathway of complement may contribute to tissue damage and organ dysfunction of antibody-mediated diseases and ischemia-reperfusion conditions. Complement factors are being considered as targets for therapeutic intervention. OBJECTIVE: We sought to characterize ARGX-117, a humanized inhibitory monoclonal antibody against complement C2. METHODS: The mode-of-action and binding characteristics of ARGX-117 were investigated in detail. Furthermore, its efficacy was analyzed in in vitro complement cytotoxicity assays. Finally, a pharmacokinetic/pharmacodynamic study was conducted in cynomolgus monkeys. RESULTS: Through binding to the Sushi-2 domain of C2, ARGX-117 prevents the formation of the C3 proconvertase and inhibits classical and lectin pathway activation upstream of C3 activation. As ARGX-117 does not inhibit the alternative pathway, it is expected not to affect the antimicrobial activity of this complement pathway. ARGX-117 prevents complement-mediated cytotoxicity in in vitro models for autoimmune hemolytic anemia and antibody-mediated rejection of organ transplants. ARGX-117 exhibits pH- and calcium-dependent target binding and is Fc-engineered to increase affinity at acidic pH to the neonatal Fc receptor, and to reduce effector functions. In cynomolgus monkeys, ARGX-117 dose-dependently reduces free C2 levels and classical pathway activity. A 2-dose regimen of 80 and 20 mg/kg separated by a week, resulted in profound reduction of classical pathway activity lasting for at least 7 weeks. CONCLUSIONS: ARGX-117 is a promising new complement inhibitor that is uniquely positioned to target both the classical and lectin pathways while leaving the alternative pathway intact.

Protein crystallization promotes type 2 immunity and is reversible by antibody treatment.

Although spontaneous protein crystallization is a rare event in vivo, Charcot-Leyden crystals (CLCs) consisting of galectin-10 (Gal10) protein are frequently observed in eosinophilic diseases, such as asthma. We found that CLCs derived from patients showed crystal packing and Gal10 structure identical to those of Gal10 crystals grown in vitro. When administered to the airways, crystalline Gal10 stimulated innate and adaptive immunity and acted as a type 2 adjuvant. By contrast, a soluble Gal10 mutein was inert. Antibodies directed against key epitopes of the CLC crystallization interface dissolved preexisting CLCs in patient-derived mucus within hours and reversed crystal-driven inflammation, goblet-cell metaplasia, immunoglobulin E (IgE) synthesis, and bronchial hyperreactivity (BHR) in a humanized mouse model of asthma. Thus, protein crystals may promote hallmark features of asthma and are targetable by crystal-dissolving antibodies.

Serum soluble HLA-E in melanoma: a new potential immune-related marker in cancer.

BACKGROUND: Tumor-derived soluble factors, including soluble HLA molecules, can contribute to cancer immune escape and therefore impact on clinical course of malignant diseases. We previously reported that melanoma cells produce, in vitro, soluble forms of the non-classical MHC class I molecule HLA-E (sHLA-E). In order to investigate sHLA-E production by various tumors and to address its potential value as a tumor-associated marker, we developed a specific ELISA for the quantification of sHLA-E in biological fluids. METHODOLOGY/PRINCIPAL FINDINGS: We developed a sHLA-E specific and sensitive ELISA and we showed that serum sHLA-E levels were significantly elevated (P<0.01) in melanoma patients (n = 127), compared with healthy donors (n = 94). sHLA-E was also detected in the culture supernatants of a wide variety of tumor cell lines (n = 98) including melanomas, kidney, colorectal and breast cancers. Cytokines regulation of sHLA-E production by tumor cells was also carried out. IFN-γ, IFN-α and TNF-α were found to upregulate sHLA-E production by tumor cells. CONCLUSIONS/SIGNIFICANCE: In view of the broad tumor tissue release of HLA-E and its up-regulation by inflammatory cytokines, sHLA-E should be studied for its involvement in immune responses against tumors. Interestingly, our results demonstrated a positive association between the presence of serum sHLA-E and melanoma. Therefore, the determination of sHLA-E levels, using ELISA approach, may be investigated as a clinical marker in cancer patients.