Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by persistent synovial inflammation, cartilage degradation, and progressive bone erosion. Although tumor necrosis factor-α (TNF-α) inhibitors are predominant to RA management, current protein-based therapies are often hindered by high costs, the need for frequent administration, and the development of drug resistance. To address the limitations, this study proposes an alternative therapeutic strategy. The aim is to utilize lipid nanoparticles (LNPs) to deliver circular RNA (circRNA) encoding adalimumab, enabling sustained endogenous production of the therapeutic antibody.

CircRNAs and liner mRNA (as control) encoding the light and heavy chains of adalimumab were designed and synthesized. An optimized LNP formulation, designated as C8-6-2-OH, was developed for encapsulation. The efficacy was evaluated in a human TNFα-transgenic mouse model following intravenous administration, compared with subcutaneously administration of adalimumab protein. All data were presented as mean ± standard deviation (SD). The experimental results were analyzed by Student’s t-test or one-way analysis of variance (ANOVA). Dunnett’s test was applied for multiple comparisons where appropriate. Across all comparisons, the difference with a p value < 0.05 was regarded as statistically significant.

In this study, the circRNAs were synthesized via group I intron autocatalysis strategy. We titrated the light-to-heavy chain ratio (LC:HC) of the antibody-encoding sequences and a 1:1 molar ratio of circRNA constructs present the highest adalimumab production both in vitro and in vivo. Our lead formulation, C8-6-2-OH LNPs demonstrated enhanced liver tropism with a 1.3-fold increase in hepatic accumulation compared with SM102 LNPs. Besides, C8-6-2-OH LNPs encapsulating circRNA enabled robust and sustained endogenous production of adalimumab following systemic administration. In a human TNF-α-transgenic mouse model, intravenous delivery of circRNAs encoding the adalimumab light and heavy chains effectively suppressed arthritis progression and ameliorated synovial inflammation and joint destruction. Histologic examination of the major organs, including heart, liver, spleen, lung and kidney revealed no evidence of injury.

Collectively, we propose an alternative therapeutic strategy by encapsulating circRNA encoding adalimumab into optimized LNPs, offering a durable and efficient approach for the treatment of RA.