Assessment of safety and intranasal neutralizing antibodies of HPMC-based human anti-SARS-CoV-2 IgG1 nasal spray in healthy volunteers

Abstract

An HPMC-based nasal spray solution containing human IgG1 antibodies against SARS-CoV-2 (nasal antibody spray or NAS) was developed to strengthen COVID-19 management. NAS exhibited potent broadly neutralizing activities against SARS-CoV-2 with PVNT₅₀ values ranging from 0.0035 to 3.1997 μg/ml for the following variants of concern (ranked from lowest to highest): Alpha, Beta, Gamma, ancestral, Delta, Omicron BA.1, BA.2, BA.4/5, and BA.2.75. Biocompatibility assessment showed no potential biological risks. Intranasal NAS administration in rats showed no circulatory presence of human IgG1 anti-SARS-CoV-2 antibodies within 120 h. A double-blind, randomized, placebo-controlled trial (NCT05358873) was conducted on 36 healthy volunteers who received either NAS or a normal saline nasal spray. Safety of the thrice-daily intranasal administration for 7 days was assessed using nasal sinuscopy, adverse event recording, and self-reporting questionnaires. NAS was well tolerated, with no significant adverse effects during the 14 days of the study. The SARS-CoV-2 neutralizing antibodies were detected based on the signal inhibition percent (SIP) in nasal fluids pre- and post-administration using a SARS-CoV-2 surrogate virus neutralization test. SIP values in nasal fluids collected immediately or 6 h after NAS application were significantly increased from baseline for all three variants tested, including ancestral, Delta, and Omicron BA.2. In conclusion, NAS was safe for intranasal use in humans to increase neutralizing antibodies in nasal fluids that lasted at least 6 h.

Figure 1

Mechanism of action of NAS. NAS provides the dual-action physical barrier on nasal mucosa by (1) forming of steric barrier at the cell surface by HPMC and (2) inhibiting SARS-CoV-2 viral particles via an anti-SARS-CoV-2 human IgG1 antibody cocktail. This figure was created with BioRender.com.

Figure 2

Biocompatibility study of NAS. (a) In vitro cytotoxicity of NAS was assessed using the direct contact method in Balb/c 3T3 cells. Cell viability percentage after 24 h of co-culture was determined. Negative (HDPE) and positive (natural rubber latex) controls were included. (b) Intracutaneous reactivity test in New Zealand white rabbits was used to evaluate the mean skin reaction scores (erythema/oedema) at different time points. The samples were intracutaneously injected (0.2 ml) at five test sites per treatment, and skin reactions were visually scored at 24, 48, and 72 h post-injection. Physiological saline was used as a negative control. (c) Swiss albino mice were orally treated with NAS at 50 ml/kg body weight to assess acute systemic toxicity. Body weight and clinical signs of toxicity were monitored. Physiological saline was used as a negative control. (d) Wistar rats were orally treated with NAS at 10 ml/kg body weight to evaluate subacute (28-day) systemic toxicity. Body weight and any clinical signs of toxicity were monitored, and hematology, clinical biochemistry, and pathology tests were performed at the end of the study. (e) Key results of the biocompatibility study of NAS are summarized.

Figure 3

Study flow chart. Thirty-eight healthy volunteers were enrolled to evaluate the safety and detect intranasal neutralizing antibodies before and after a placebo or NAS application. Thirty-six volunteers were randomized into a 1:3 ratio to receive a placebo (n=9) and NAS (n=27), while the other 2 were excluded due to nasal polyps. Safety was assessed using sinuscopy, adverse event recording, and self-reporting questionnaires. SARS-CoV-2 neutralizing antibodies were detected in the nasal fluids taken from volunteers pre- and post-administration.

Figure 4

Representative nasal sinuscopy images after NAS application. The participants’ nasal sinus in both nostrils was imaged using a sinuscope on days 0, 7, and 14. No inflammation signs or any appearance changes were observed.

Figure 5

Assessment of SARS-CoV-2 neutralizing antibodies in nasal fluids before and after a placebo or NAS application. SARS-CoV-2 neutralizing antibodies in nasal fluids swabbed from pre- and post-product administration were detected using the cPass SARS-CoV-2 surrogate virus neutralization test. (a) Illustration of study design. SIP values against (b) ancestral, (c) Delta, and (d) Omicron BA.2 variants before and immediate or 6-h time point after a placebo or NAS application. Data are presented in IQR ± 25th–75th percentile.