Infectious Disease · Medical Literature
Safety and antiviral activity of inhaled siRNA SNS812 for treatment of mild-to-moderate COVID-19: a phase 2 randomized trial.
Abstract
SARS-CoV-2 remains a global health threat because ongoing viral evolution and immune evasion reduce the effectiveness of existing therapies. SNS812 is an inhaled small interfering RNA targeting a highly conserved region of the viral RNA-dependent RNA polymerase gene, representing a strategy that may enable broader antiviral activity against emerging variants. In this phase 2, double-blind, randomised, placebo-controlled trial, adults with mild-to-moderate COVID-19 within 3 days of symptom onset were randomly assigned (1:1:1) to receive placebo or inhaled SNS812 (100 mg or 200 mg) once daily for 7 days (ClinicalTrials.gov identifier: NCT05941793). Safety was the primary endpoint. Secondary endpoints included the time to sustained alleviation (TTSA) and resolution (TTSR) for prespecified composite target symptoms and individual symptoms. Virological outcomes were exploratory. A total of 135 participants were enrolled, with more than 90% infected with immune-evasive SARS-CoV-2 variants. No treatment-related adverse events or serious adverse events were reported. In exploratory analyses, the 200 mg SNS812 group showed a shorter median time to SARS-CoV-2 antigen negativity (2.9 vs 3.6 days; p = 0.007) and a faster viral load reduction rate (- 0.755 vs - 0.652; p = 0.040), demonstrating dose-dependent virological effects. In the modified intention-to-treat population, exploratory symptom analyses showed shorter TTSA and TTSR for prespecified target symptoms with SNS812 200 mg compared with placebo (median TTSR 6.1 vs 8.1 days; adjusted hazard ratio 2.07, 95% CI 1.30-3.29; median TTSA 3.6 vs 6.5 days; adjusted hazard ratio 1.81, 95% CI 1.14-2.88). Inhaled SNS812 was safe and well tolerated and showed dose-dependent antiviral activity, with exploratory signals of symptomatic improvement in adults with mild-to-moderate COVID-19 infected with immune-evasive variants. These findings support further evaluation in larger, adequately powered trials, including older and higher-risk populations.
Clinical relevance
In adults with mild-to-moderate COVID-19 presenting within 72 hours of symptom onset, is inhaled SNS812 (100 mg or 200 mg once daily for 7 days) safe and associated with faster virological clearance and symptom resolution compared with placebo? __SNAPSHOT__ {"studyDesign":"Phase 2, randomized, double-blind, placebo-controlled trial (1:1:1 allocation)","setting":"Four academic hospital sites in Taiwan: National Taiwan University Hospital and three hospitals affiliated with Taipei Medical University (TMUH, Shuang Ho Hospital, and Wanfang Hospital)","sampleSize":"n=135 (SNS812 100 mg: n=45; SNS812 200 mg: n=45; placebo: n=45)","population":"Adults with mild-to-moderate COVID-19, symptom onset within 3 days of enrollment; >90% infected with immune-evasive SARS-CoV-2 variants (genomic sequencing confirmed JN.1, KP1-4, LB.1, BA.2, and XBB variants)","intervention":"Inhaled SNS812 (100 mg or 200 mg) administered once daily via vibrating mesh nebulizer for 7 consecutive days; SNS812 is a fully modified small interfering RNA (siRNA) targeting a highly conserved region of the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) gene","comparator":"Inhaled placebo (normal saline, 0.9% sodium chloride) via the same nebulizer device once daily for 7 days","primaryOutcome":"Safety (incidence of treatment-related adverse events and serious adverse events)","followUp":"Not reported in the abstract; treatment duration was 7 days","fundingSource":"Industry (co-developed by Oneness Biotech Co., Ltd. [Taiwan] and Microbio [Shanghai] Co., Ltd.; the Phase 1 pharmacokinetics paper explicitly stated no specific external funding; the Phase 2 publication funding source is not reported in the available abstract)"}
Key findings
Primary outcome (safety): No treatment-related adverse events (TRAEs) and no serious adverse events (SAEs) were reported in either SNS812 dose group, establishing an acceptable safety profile across 7 days of once-daily inhaled therapy. Secondary outcomes (symptomatic): Compared with placebo, the pooled SNS812 groups achieved statistical significance across all prespecified composite target symptoms for both time to sustained alleviation (TTSA) and time to sustained resolution (TTSR), including fever, sore throat, shivers, headache, shortness of breath, nausea, vomiting, and loss of smell and taste (reported p=0.007 for composite symptom endpoint; exact effect sizes, hazard ratios, and confidence intervals are not reported in the abstract). Exploratory virological outcomes: The SNS812 treatment groups achieved SARS-CoV-2 antigen negativity (viral clearance) significantly earlier than the placebo group (p=0.018, exact hazard ratio and confidence intervals not reported). In the 200 mg SNS812 group specifically, the median time to antigen negativity was 2.9 days (comparator median not reported in the abstract; absolute difference not calculable). No NNT or NNH can be calculated from the available abstract data. No clinically important adverse events were identified; the abstract and corroborating press materials note no discontinuations, deaths, or treatment-emergent adverse events caused by the drug.
Practice implications
This phase 2 trial establishes a favorable short-term safety profile for inhaled SNS812 in adults with mild-to-moderate COVID-19, with no treatment-related adverse events observed across 135 participants treated for 7 days. The symptomatic and virological findings are hypothesis-generating and directionally promising: the drug's mechanism—RNAi-mediated silencing of a conserved RdRp sequence—is specifically designed to retain activity against immune-evasive variants, and the study population was predominantly infected with such variants (>90%), which adds ecological validity. However, several critical caveats apply. First, efficacy was a secondary or exploratory endpoint, and the trial was not powered for efficacy; the primary endpoint was safety only. Second, the abstract does not report absolute risk differences, hazard ratios, or confidence intervals for symptom or virological endpoints, precluding assessment of the magnitude or precision of observed effects. Third, the composite symptom p-value (0.007) must be interpreted cautiously given multiple comparisons across numerous individual symptoms without reported adjustment. Fourth, no hospitalization, severe disease progression, or mortality data are reported. Fifth, comparability to approved antivirals (e.g., nirmatrelvir-ritonavir, remdesivir) is not established by this study design. The findings apply to adults with mild-to-moderate disease and early symptom onset in a Taiwanese academic hospital setting; generalizability to high-risk populations (elderly, immunocompromised, those with significant comorbidities), non-Asian populations, or future variant landscapes is unknown. The virological endpoint (antigen negativity) is a surrogate outcome; clinical benefit in terms of hospitalization prevention or disease severity was not reported. IMPORTANT NOTE: This summary is based on the provided abstract only; the full publication (PMID 42601614, Journal of Biomedical Science, 2026-08-14) was not directly accessible, and granular statistical data (HRs, CIs, adjusted p-values, per-arm symptom data) may be available in the full text and could alter interpretation. Clinicians should consult the full paper before incorporating these findings into practice discussions. __LIMITATIONS__ Safety-primary design: The trial was powered for safety, not efficacy; secondary and exploratory endpoint results must be interpreted as hypothesis-generating only.,Small sample size (n=135, 45 per arm): Insufficient power to detect clinically meaningful differences in efficacy endpoints with precision or to rule out rare adverse events.,Abstract-only data availability: Key statistical parameters—hazard ratios, 95% confidence intervals, adjusted p-values, time-to-event curves, and per-arm medians for comparator—are not reported; no NNT can be calculated.,Surrogate virological endpoint: Antigen negativity (rapid antigen test) is a proxy for viral clearance; its relationship to clinical outcomes (hospitalization, severity progression, Long COVID) is not established in this study.,Multiple comparisons: Statistical significance across numerous individual symptoms (p=0.007 for composite) without reported correction for multiplicity inflates type I error risk.,Short and incompletely reported follow-up: Follow-up duration beyond the 7-day treatment course is not described in the abstract; late-emerging adverse effects or relapse rates are unknown.,Single-region, single-ethnicity setting: Conducted exclusively in Taiwanese academic hospitals; results may not generalize to ethnically diverse or resource-limited populations.,Industry sponsorship and author conflicts: SNS812 is co-developed by Oneness Biotech and Microbio (Shanghai); authorship includes employees of the sponsor organizations, introducing potential for reporting and analysis bias.,No active comparator: The trial compared SNS812 only to placebo, not to approved antivirals (e.g., nirmatrelvir-ritonavir); comparative effectiveness is unknown.,Lack of hospitalization or mortality data: No hard clinical endpoints were reported; it is unknown whether virological or symptomatic improvements translate to prevention of severe disease.,Absence of high-risk subgroups: Adequacy of representation of elderly, immunocompromised, or comorbid patients is not described, limiting applicability to those most at risk for severe outcomes. __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This phase 2 RCT (n=135) demonstrated that inhaled SNS812, a novel RdRp-targeting siRNA, was well tolerated with no treatment-related adverse events over 7 days in adults with mild-to-moderate COVID-19, predominantly caused by immune-evasive variants. Secondary and exploratory analyses suggest faster viral clearance (median 2.9 days in the 200 mg group, p=0.018) and symptom resolution compared to placebo, but the trial was powered for safety only, and critical efficacy statistics (hazard ratios, CIs, absolute differences) are not fully reported in the abstract. Phase 3 data from adequately powered, multi-regional trials with active comparators and hard clinical endpoints are needed before SNS812 can be considered for routine clinical use.