Background Anti-citrullinated peptide antibodies (ACPA) appear 10–15 years before the diagnosis of rheumatoid arthritis (RA) and are associated with a more severe disease course. In previous work, we rationally designed and screened ACPA-binding peptide aptamer sequences in silico and constructed a nanoparticle with chitosan and hyaluronic acid(1). A developmental stage version of this nanoparticle was able to reduce disease activity in the collagen-induced arthritis (CIA) and the serum transfer arthritis mouse models (2).

Objectives Here, we investigated the effect and potential toxicity of three different versions of the aptamer nanoparticle (loading of 20%, 10% and 5% aptamer, respectively) in the CIA rat model.

Methods Wistar rats (males and females) were given a single intravenous dose (100 mg/kilo) of type II collagen in PBS in the tail vein. The dosing was repeated three times with one day interval, followed by blood sample collection at day 7 after the initial collagen injection. To evaluate route of administration and dosing, we injected a single intravenous and subcutaneous dose (2.5 mg/kg) of aptamer-nanoparticles (A/N ratio 20%) in PBS in the tail vein/abdomen, and plasma concentration−time profiles were followed for 2 days after dosing with weekly blood sampling. To evaluate organ uptake, rats were given a single intravenous and subcutaneous dose (2.5 mg/kg) of aptamer-nanoparticles (A/N ratio 20%) in PBS in the tail vein/abdomen. The procedure was repeated after 24 hours. Blood and urine samples were taken once a week. A group of 10 animals was sacrificed every week over a three-week period, and the organs were processed. To examine efficacy, rats were given a single subcutaneous dose (2.5 mg/kilo) of aptamer-nanoparticles and nanoparticle controls without aptamer or PBS alone in the abdomen. The procedure was repeated once a week over a course of three weeks. Weight, joint measurement, blood, and urine samples were taken once a week. Paw swelling was measured on a weekly basis. In the plasma samples we measured CPEP2 and anti-collagen II by enzyme linked immunosorbent assay (ELISA).

Results Using a rather high dose of collagen (100 mg/kilo) via an intravenous administration route, ACPA was measurable in all CIA rats with rapid development of RA in 82% of the included animals. Intravenous administration resulted in an immediate high plasma concentration post injection, which decreased rapidly to low levels. The s.c. administration route gave a steady, long-term aptamer release with a maximum availability 8 hours post-injection. After three aptamer-nanoparticle doses (2.5 mg/kg; either 20%, 10% or 5% aptamer), we observed a dose-dependent reduction in swollen joint count for the aptamer-nanoparticle treated groups (10 rats in each group) compared with the healthy control group (10 rats) (P-value = 2,1E-6). We observed decreased ACPA IgG levels in the rats treated with aptamer-nanoparticle. The decrease in ACPA levels correlated with the aptamer-nanoparticle having higher loading. Anti-collagen II IgG levels slightly increased towards the end of the study.

Conclusion We developed and tested a novel peptide aptamer-based drug candidate for seropositive rheumatoid arthritis in CIA rats. Over a 3-week course of treatment with subcutaneous administration of aptamer-nanoparticles, joint swelling was decreased during treatment, and completely reversed at the end of the observation period. The reduction of joint swelling was associated with decreased levels of ACPA in the blood.

References [1]Khatri S, Hansen J, Mendes AC, et al. Citrullinated Peptide Epitope Targets Therapeutic Nanoparticles to Human Neutrophils. Bioconjug Chem. 2019;30(10):2584-2593. doi:10.1021/acs.bioconjchem.9b00518

[2]Khatri S, Hansen J, Clausen MH, et al. LB0002 A FIRST IN CLASS THERAPEUTIC NANOPARTICLE FOR SPECIFIC TARGETING OF ANTI-CITRULLINATED PROTEIN ANTIBODY AMELIORATES SERUM TRANSFER AND COLLAGEN INDUCED ARTHRITIS. Annals of the Rheumatic Diseases 2020;79:212.

Disclosure of Interests Sangita Khatri: None declared, Jonas Hansen: None declared, Nadia Pedersen: None declared, Sanne Gram-Nielsen: None declared, Ana Mendes: None declared, Ioannis Chronakis: None declared, Ulrik Keiding: None declared, Bence Réthi: None declared, Mads Hartvig Clausen Shareholder of: affiliated with IBIO TECH ApS, Tue Wenzel Kragstrup Shareholder of: affiliated with IBIO TECH ApS, Speakers bureau: TWK received speaking fees from Pfizer, Bristol-Myers Squibb, Eli Lilly, Novartis, UCB, and Abbvie., Consultant of: Consultancy fees from Bristol-Myers Squibb and Gilead, Grant/research support from: Received research grant from Gilead, Kira Astakhova Shareholder of: KA is affiliated with iBio tech.