Details

Autor(en) / Beteiligte

• Branch, Donald
• Loriamini, Melika
• Lewis-Bakker, Melissa
• Boligan, Kayluz Frias
• Kotra, Lakshmi

Titel

3040 – DRUG DISCOVERY FOR INHIBITORS OF PHAGOCYTOSIS FOR USE IN IMMUNE CYTOPENIAS

Ist Teil von

• Experimental hematology, 2022, Vol.111, p.S64-S65

Ort / Verlag

Elsevier Inc

Erscheinungsjahr

2022

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Immune cytopenias, ITP, AIHA, HTR, DHTR, HDFN and autoimmune neutropenia (AIN), occur when the body produces antibodies against certain hematopoietic cells. Activating Fcγ receptors (FcγRs) on monocyte-macrophages in the spleen and/or liver induces extravascular antibody-mediated phagocytosis, resulting in the destruction of the opsonized blood cells. 80 compounds from a chemical library of 5000 molecules were tested for inhibition of in vitro phagocytosis of anti-D-opsonized Rh-positive RBCs. Four were further tested and found to have negligible toxicity (up to 250 μM) against PBMCs, liver HEPG2 and kidney HEK293 cell lines using LDH release, MTT viability and apoptosis. Attachment of antibody-opsonized RBCs’ to FcγRs was evaluated at room temperature using fluorescent dye-labeled opsonized RBCs. Tests using F(ab’)2 monoclonal antibodies to FcγRI (CD64), FcγRIIa/b (CD32) and FcγRIII (CD16) were done to determine if the compounds could block the binding to FcγRs. In the phagocytosis assay; four molecules (5 µM) showed ≥ 69% inhibition compared to 100% by IVIG (6.5 μM). Two molecules showed negligible toxicity in all assays, lowest IC50 values (3 and 4 µM) and no synergism with IVIG in a dose-inhibitory response curve. Like IVIG, these two molecules prevented rosette formation by antibody-opsonized RBCs. Subsequently, efficacy of selected lead compounds to ameliorate experimental ITP was assessed. One molecule was tested and able to ameliorate mouse ITP at 1 mg/kg in comparison to IVIG at 2 g/kg. This molecule was selected as a lead compound for further preclinical studies. We have thus identified a small molecule drug as a lead compound for potential use as a phagocytosis inhibitor in cases of immune cytopenia.