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Background: APN01 is a soluble recombinant human angiotensin-converting enzyme 2 (rhACE2), a key player in the renin-aldosterone-angiotensin system (RAAS). In clinical studies, APN01 was administered intravenously only, so far. The aim of this study (ClinicalTrials.gov: NCT05065645) was to evaluate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of inhaled APN01., Methods: This was a phase I, double-blind, placebo-controlled, dose-escalation study. Inhalation was conducted via a nebuliser over 15 min in three single ascending dose (SAD) cohorts (n=24) and two multiple ascending dose (MAD) cohorts (n=16: every 12 h for 7 days). Doses in the SAD cohort were 1.25, 2.5 and 5 mg·mL -1 ; doses in the MAD cohort were 2.5 and 5 mg·mL -1 . Safety (including adverse events (AEs), laboratory findings and lung function results), PK and PD data were assessed., Results: In the SAD and MAD cohorts, treatment-related AEs were slightly more frequent in the active treatment group than in the placebo group. AEs were mild to moderate, with no dose-limiting toxicities. No clinically relevant changes in lung function and laboratory results were observed. The mean maximum observed plasma concentration ( C max ) values after single and multiple doses of 5 mg·mL -1 APN01 were 1.88 and 6.61 ng·mL -1 , respectively. Among the PD variables, significance was found for ACE2 and angiotensin 1-5., Conclusions: The application of aerosolised APN01 is safe and well tolerated after single and multiple doses. By achieving a high local concentration in the lungs and low systemic bioavailability, inhaled rhACE2 may present a therapeutic option in ACE2-related diseases., Competing Interests: Conflict of interest: This work was supported by Apeiron Biologics and conducted as contract research at the Medical University of Vienna, Department of Pulmology and Department of Clinical Pharmacology. The funder did not have any role in the execution of the study or interpretation of data. The academic authors declare no conflict of interest., (Copyright ©The authors 2024.)

The recent emergence of multiple SARS-CoV-2 variants has caused considerable concern due to both reduced vaccine efficacy and escape from neutralizing antibody therapeutics. It is, therefore, paramount to develop therapeutic strategies that inhibit all known and future SARS-CoV-2 variants. Here, we report that all SARS-CoV-2 variants analyzed, including variants of concern (VOC) Alpha, Beta, Gamma, Delta, and Omicron, exhibit enhanced binding affinity to clinical grade and phase 2 tested recombinant human soluble ACE2 (APN01). Importantly, soluble ACE2 neutralized infection of VeroE6 cells and human lung epithelial cells by all current VOC strains with markedly enhanced potency when compared to reference SARS-CoV-2 isolates. Effective inhibition of infections with SARS-CoV-2 variants was validated and confirmed in two independent laboratories. These data show that SARS-CoV-2 variants that have emerged around the world, including current VOC and several variants of interest, can be inhibited by soluble ACE2, providing proof of principle of a pan-SARS-CoV-2 therapeutic., (©2022 The Authors. Published under the terms of the CC BY 4.0 license.)