Publication date: Jul 17, 2025

This study aimed to evaluate the safety, tolerability, pharmacokinetics (PK), immunogenicity, and serum neutralizing activity of a single dose of SA55 injection in healthy individuals. A randomized, controlled, double-blind trial was conducted with 40 healthy volunteers aged 18-65 years. Participants received a single intramuscular injection of the investigational product at four dose levels (150 mg, 300 mg, 600 mg, and 900 mg), with randomization stratified by dose cohort. Dose proportionality and linearity of PK parameters (AUC, AUC, and C) were assessed using one-way ANOVA and the Power model, while neutralizing the activity against the EG. 5 strain, and safety outcomes were monitored. Results demonstrated that SA55 injection was safe and well-tolerated at doses ranging from 150 mg to 900 mg, with a half-life of 94-103 days and no significant dose-dependent trends. C, AUC, and AUC showed an approximately linear relationship with dosage, while T decreased as the dosage increased. The levels of ADA of all positive participants were at low levels, and the cumulative positive rates among treatment groups were similar to that of the placebo group. The neutralizing activity peaked at 3-4 days post-administration, with the 600 mg dose exhibiting comparable activity to the 900 mg dose and superior activity to lower doses, suggesting it as a potential target dose. In conclusion, SA55 injection demonstrated excellent safety, tolerability, and neutralizing activity against SARS-CoV-2 in healthy populations, with the 600 mg dose emerging as a promising candidate for further development. CLINICAL TRIALSThis study is registered with ClinicalTrials. gov as NCT06050460.

Original Article