Rhinitis is a type of upper respiratory infection with a common nasal pathology especially in Southeast Asia, which is characterized by the presence of one or more of the following symptoms: itchy nose, sneezing, runny nose, and nasal congestion. The treatment of acute rhinosinusitis and allergic rhinitis in hospitals is currently carried out according to the general professional guidance of the Vietnam Ministry of Health. A common treatment regime for patients with rhinosinusitis in Vietnam includes a combination of steroids and antibiotics (Neomycin/Dexamethasone/ Xylometazoline) administered as a nasal spray, in adjunct with Amoxicillin/clavulanate 875/125 mg taken orally every 12- hours. The duration of treatment for patients is about 10 days depending on the severity of the disease. During the treatment period, a change in the systemic antibiotic regimen is necessary if the observations after 3 to 5 days of treatment do not show signs of a satisfactory response.

Current concerns about antimicrobial resistance (AMR) as well as side effects of corticosteroids and antihistamines have led to an urgent need for a naturebased next generation therapeutic approach that is safe, effective and helps in addressing the issues of AMR.

There have been multiple research studies supporting the efficacy of bacterialbased approaches in the prevention of viral respiratory infections, and that have potential for treatment. For use in the respiratory tract, it is necessary to have a completely sterile product to ensure safety in the long-term and there is a need for safety assessment of products both in animal models and human studies.

This phase of the study aims to evaluate the safety in humans of a nasal spray using a postbiotic preparation of Bacillus subtilis DSM32444 and that is a sterile inert bioparticle.

Rhinitis is a type of upper respiratory infection and a common nasal pathology especially in Southeast Asia, which is characterized by the presence of one or more of the following symptoms: itchy nose, sneezing, runny nose, and nasal congestion. Other symptoms occasionally experienced include headache, excessive pain reaction, cough, fever. Rhinitis can be idiopathic or due to a variety of causes, including allergens, medications, endocrine/metabolic, infectious, inflammatory, and abnormal nasal structures. Rhinosinusitis in general is not a dangerous pathological condition, however the frequency of the disease is relatively high with statistics showing that all people experience it at least once in their lives. Common rhinosinusitis symptoms include severe facial pains and difficulties in breathing. Hence, most patients are prescribed corticosteroids, antihistamines, and antibiotics for immediate decongestion and anti-inflammatory effects. Current concerns about antimicrobial resistance (AMR) as well as the documented side effects of corticosteroid and antihistamine have led to an urgent need for a nature-based next generation therapeutic approach that is safe, effective and helps in addressing AMR problem. Preclinical studies of inactivated Bacillus subtilis strain DSM32444 conducted by collaborating UK universities and laboratories have shown potential therapeutic benefits with anti-inflammatory mechanisms that may be useful in other viral infections of the respiratory tract. The reason for using an inactivated spore is because various publications have identified risks of inhalation of high doses of live bacteria in the respiratory tract and lungs. DSM32444 also carries GRAS status for human use. An accredited, cGLP, repeat-dose toxicology study also confirmed complete safety in rodent models after high doses of treatment.

The investigators think there is a likelihood to apply this postbiotic technology to mitigate the overuse of antibiotics, corticosteroids, and antihistamines. The aim of this study is to evaluate the safety nasal spray using the postbiotic Bacillus subtilis DSM32444 when used in humans.

• Study population: Sample size for Phase 1 is 60 healthy volunteers to assess tolerance.
• Description of Sites: the study is carried out at Thai Binh University of Medicine and Pharmacy and Thai Binh University of Medicine and Pharmacy Hospital.
• Description of Study intervention:

The Phase I study is a double-blind, parallel-group, randomized, placebo controlled study. Study participants who are healthy volunteers were randomly assigned 1:1 to either the postbiotic DSM32444 nasal spray (SPEROVID) or the placebo (0.9% NaCl). Study subjects who are healthy volunteers, confirmed by routine physical examination of the research facility, will be invited to participate in the phase I study. The randomization is carried out according to the 4-block strategy using envelopes with predetermined random codes. Study subjects will be given codes in turn sealed in sequentially numbered envelopes. The research product is prepared in a double-blind form, on the label there are random codes matching the code assigned to the study object. The duration of the study regimen is 7-days, except for early withdrawal from the study for safety reasons. The research product (SPEROVID or placebo) is nasally administered as a spray 2-3 times daily, with each administration being 0.1ml/nostril (total 0.2 mL/administration). Researchers will follow up with volunteers for safety evaluation of the products, analysis of the subject's complaints of disease and other special issues (if applicable), physical examination and laboratory tests. If any adverse events are detected, the investigator should immediately record the information in the source literature and CRF, specifying the nature of the AE, the duration of the AE, and other characteristics.

• The study data after collection will be analyzed statistically using SAS 9.4. The normal distribution of statistical samples will be evaluated by the Kolmogorov- Smirnov-Lilliefors test, the uniformity of variance will be verified by Levene's test. The continuous variables will be analyzed using a two-dimensional variance test or covariance analysis (ANOVA/ANCOVA) in the case of a normal distribution and using the ANOVA non-parametric Kruskal-Wallis test in the case of a non-standard distribution. Repeatable measurement analyses will be used where appropriate. Differences between treatment groups in terms of duration of major symptoms of acute respiratory infection and average time to resolution will be assessed using the Student's t-test or the Mann-Whitney test. Chi-Square (or Fisher's exact test) will be used to evaluate the difference between the ratios. Analysis of classification data is carried out using the Cochran-Mantel Haenszel test. In the absence of further note, the continuous variables are expressed by the mean ± standard deviation. The Cox analysis model and log-rank testing will be used to compare variables of the time type leading up to an event.
• Expected outcomes: The nasal spray using postbiotic Bacillus subtilis DSM32444 (SPEROVID) is safe and well tolerated among healthy volunteers.

Inclusion Criteria:

• Healthy volunteers must be ≥18 years of age, at the time of signing the informed consent.
• Participants who are able to use an e-Diary or Paper Diary during the study to report their health status
• Participants capable of giving a signed informed consent form (ICF)

Exclusion Criteria:

• Planned travel outside of the study area during the study period.
• Use of any investigational drug within 30 days prior to Day screening. No investigational products are permitted for use during the conduct of this study
• A known history of alcohol or drug abuse within the last 2 years
• Existence of any medical condition, which in the opinion of the investigator, might significantly affect the subject's ability to complete this trial; or their safety in this trial