A first-in-class therapeutic nanoparticle drug has been developed for the specific targeting of anti-citrullinated protein antibodies, which may be a promising agent for targeting antibodies to citrullinated proteins and peptides (ACPAs). These findings may lead to a new therapeutic option for patients with rheumatoid arthritis.
“Several in vitro studies have suggested a pathogenic role of ACPAs in rheumatoid arthritis,” according to Prof. Kira Astakhova (Danish Technical University, Denmark) . It was hypothesized that reducing ACPA levels would have a therapeutic effect by blocking cytokine production. Thus, a series of therapeutic nanoparticles for specific targeting of ACPA in synovial fluid was prepared and tested. Nanoparticles were prepared by the microdroplet method and then decorated with synthetic cyclic citrullinated peptide aptamer PEP2, PEG/hexanoic acid and fluorophore (Cy5.5).
The nanoparticles were used in a series of in vitro assays and studies including disease activity scores, cytokine measurements, and near-infrared imaging. A fibrinogen-derived 21-amino-acid-long citrullinated peptide with high selectivity toward autoantibodies in rheumatoid arthritis samples was then identified. Subsequently, this aptamer was incorporated in the chitosan-hyaluronic acid nanoparticle formulation. The average nanoparticle size was 230 nm ± 10 nm measured by dynamic light scattering (DLS) and scanning electron microscopy (SEM), z potential was -0.0012, and purity by high-performance liquid chromatography (HPLC) was >95%. Attachment efficiency of the aptamer was 92% by HPLC. FACS study showed selective uptake of Cy5.5 labelled aptamer-nanoparticle conjugates by neutrophils in the concentration range 0.5-4 nM. No apparent immunogenicity for this nanoparticle formulation M was demonstrated, which is in line with results from other trials .
A reduction of disease activity of over 50% was achieved in vivo in 3 weeks treatment using as little as 1 nM drug candidate (dosed every 48 hours) in the collagen-induced (CIA) mouse model of rheumatoid arthritis (n=30). The same was seen in the serum transfer model (n=10). The aptamer-nanoparticle conjugate significantly reduced IL-6 and TNFα levels in the mouse sera. The effects were not inferior to tocilizumab treated controls (n=30). The mode of action was then confirmed by applying Cy5.5-labelled aptamer-nanoparticles in the collagen-induced mouse model (n=10). An over 6-fold higher signal accumulation in inflamed versus healthy joints was confirmed; this strongly supports the highly specific nature of the aptamer with regard to the inflammatory process.
1. Khatri S, et al. A first in class therapeutic nanoparticle for specific targeting of anti-citrullinated protein antibody ameliorates serum transfer and collagen induced arthritis. Abstract LB0002. EULAR E-Congress, 3-6 June 2020.
2. Khatri S, et al. Citrullinated Peptide Epitope Targets Therapeutic Nanoparticles to Human Neutrophils. Bioconjug Chem. 2019 Oct 16;30(10):2584-2593.