Nanoparticle Treatment Showing Promise Against Rheumatoid Arthritis

Kira Astakhova, PhD

Investigators continue to test new methods, such as nanoparticles, to treat rheumatoid arthritis (RA).

In data planned for presentation during the European Congress of Rheumatology (EULAR) 2020 meeting, a team, led by Kira Astakhova, PhD, Stanford University, examined whether reducing antibodies to citrullinated proteins and peptides (ACPAs) could have a therapeutic effect by blocking cytokine production in patients with rheumatoid arthritis.

While several in vitro studies have pointed to a pathogenic role of ACPAs in the disease, there has not been in vivo proof showing this concept has been hampered by a lack of therapeutic strategies to either reduce or deplete antibodies to citrullinated proteins and peptides in serum and synovial fluid.

In the past, the research team constructed a chitosan-hyaluronic acid nanoparticle formulation able to use neutrophil recruitment as a delivery mechanism to inflamed joints, which specifically got phagocytosed and then released to synovial fluid upon death of the short-lived neutrophils.

The nanoparticles were developed using the microdroplet method, and was then decorated with synthetic cyclic citrullinated peptide aptamer PEO2, PEG/hexanoic acid and fluorophore (Cy5.5). The investigators characterized the nanoparticles by dynamic light scattering, scanning electron microscopy (SEM), and high-performance liquid chromatography.

The investigators then used the nanoparticles in a series of in vitro assays, including cell uptake with flow cytometry (FACS) detection, and in vivo studies including disease activity scores, cytokine measurements, and near-infrared imaging.

The team also screened a series of citrullinated peptide epitopes and identified a fibrinogen-derived 21-amino-acid-long citrullinated peptide showing high selectivity toward autoantibodies in rheumatoid arthritis samples.

The average nanoparticle size was 230 nm ± 10 nm by DLS and SEM and the z potential was -0.0012. In addition, the purity by HPLC was 95%. And attachment efficiency of the aptamer was 92% by HPLC.

The FACS study showed selective uptake of Cy5.5 labelled aptamer-nanoparticle conjugates by neutrophils in the concentration range 0.5-4 nM, but similar to previous studies, there was no apparent immunogenicity for this nanoparticle formulation measured by cytokine secretion from human peripheral blood leukocytes.

In vivo, the researchers found an over 50% reduction in disease activity after 3 weeks of treatment using as little as 1nM drug candidate dosed every 48 hours in the collagen-induced mouse model of RA (n = 30; P <0.001 for treated vs placebo).

The same thing was observed in the serum transfer model (n = 10).

“Overall, we have designed a first-in-class therapeutic nanoparticle drug for specific targeting of anti-citrullinated protein antibodies,” the authors wrote. “The marked effect of this nanoparticle observed in vivo holds promise for targeting ACPAs as a therapeutic option in RA.”

Treatment for rheumatoid arthritis has improved in recent years. Last August, the US Food and Drug Administration (FDA), approved upadacitinib (RINVOQ) for the treatment of adults with moderately to severely active RA who have an inadequate response or intolerance to methotrexate.

Outcome improvements were notably significant for patients who had also reported inadequate response or intolerance to methotrexate or other monotherapies. Some patients administered 15 mg or 30 mg upadaticinib reported improved joint pain within 2 weeks.

The study, “A First In Class Therapeutic Nanoparticle For Specific Targeting of Anti-Citrullinated Protein Antibody Ameliorates Serum Transfer and Collagen Induced Arthritis,” was published online in EULAR.