Announcement on voluntary disclosure of subsidiary YKYY018 aerosol inhalation's indications for treating and preventing human metapneumovirus infection and obtaining FDA clinical trial approval

Securities code: 688658 Securities abbreviation: Yuekang Pharmaceutical Announcement number: 2026-020 Yuekang Pharmaceutical Group Co., Ltd.

About Voluntary Disclosure of Subsidiary YKYY018 Aerosol Inhaler

Indications for the treatment and prevention of human metapneumovirus infection

Announcement of FDA Clinical Trial Approval

The company's board of directors and all directors guarantee that the contents of this announcement do not contain any false records, misleading statements or major omissions, and assume legal responsibility for the authenticity, accuracy and completeness of its contents in accordance with the law.

Beijing Yuekang Science and Technology Co., Ltd. (hereinafter referred to as "Yuekang Science and Technology"), a wholly-owned subsidiary of Yuekang Pharmaceutical Group Co., Ltd. (hereinafter referred to as the "Company"), recently received a letter from the U.S. Food and Drug Administration (hereinafter referred to as the "FDA") approving the clinical trial application for YKYY018 aerosol inhalation for the treatment and prevention of human metapneumovirus (Study May Proceed Letter, IND number: 180432). The relevant information is now announced as follows:

1. Main contents of the letter:

1. Drug name: YKYY018 aerosol inhalation agent

2. IND number: 180432

3. Application indication: treatment and prevention of human metapneumovirus infection

4. Applicant: Beijing Yuekang Kechuang Pharmaceutical Technology Co., Ltd.

5. Application stage: clinical trial

6. Approval conclusion: The clinical trial application for YKYY018 aerosol inhalation has been approved by the US FDA, which agrees to conduct clinical trials of this product in accordance with the submitted plan.

2. Other situations

1. About human metapneumovirus

Human metapneumovirus (hMPV) is a single-stranded, non-segmented negative-sense RNA virus of the genus Metapneumovirus in the family Pneumoviridae. It is mainly transmitted through droplets and close contact, and can also be transmitted indirectly through contact with items contaminated by the virus. hMPV is a common cause of upper respiratory tract infections in infants and children under 5 years of age, and infants, older adults, and people with medical conditions such as immunosuppression, chronic obstructive pulmonary disease, and asthma are at higher risk of severe disease.

2. About YKYY018 aerosol inhalation agent

YKYY018 aerosol inhalation is an internationally original membrane fusion inhibitor drug independently developed by the company relying on the full-process AI platform. The product has been approved and issued by the U.S. Food and Drug Administration (FDA) and the National Medical Products Administration (NMPA) in November and December 2025, respectively, regarding the clinical trial of YKYY018 aerosol inhalation for the prevention and treatment of respiratory syncytial virus infection. For details, please see "Yuekang Pharmaceutical Group Co., Ltd. on Voluntary Disclosure of Subsidiaries" Announcement that YKYY018 aerosol inhalation product has been approved for clinical trials by the FDA" (Announcement No.: 2025-049), "Announcement of Yuekang Pharmaceutical Group Co., Ltd. on voluntary disclosure that its subsidiary YKYY018 aerosol inhalation product has been approved for clinical trials by the State Food and Drug Administration" (Announcement No.: 2025-050). The clinical phase I study of the YKYY018 project for respiratory syncytial virus (RSV) infection is progressing steadily. The approval of human metapneumovirus treatment and prevention indications marks the comprehensive expansion of the pipeline layout from a single virus to an important respiratory virus spectrum, providing more comprehensive prevention and treatment options for high-risk groups such as infants and the elderly.

This product has a new mechanism of action. It can specifically bind to the heptapeptide repeat sequence region 1 (HR1) of the F1 subunit of the pre-fusion F protein (pre-F) of respiratory syncytial virus and human metapneumovirus, inhibit the formation of homologous 6-HB between the HR1 and HR2 domains of the virus itself, block the fusion process of the virus and host cells, achieve antiviral effects, and have dual functions of treatment and prevention. The company has obtained the core patent authorization for this product and has its global exclusive rights.

Preclinical research results show that the product has significant inhibitory effects on a variety of respiratory syncytial virus strains and human metapneumovirus; in the preventive and therapeutic model efficacy tests on cotton rats, YKYY018 aerosol inhalation can significantly reduce virus titers; in terms of safety, it has been tested on Sprague-Dawley rats and In the test of Beagle dogs, YKYY018 did not have a significant impact on respiratory function. No abnormal changes related to the drug were found in the general condition, body weight and food intake, hematology and blood biochemical indicators, T lymphocyte subgroups, urine and ophthalmological examinations, organ weights and coefficients, gross anatomy observation and histopathological examination of all tested animals, indicating that it is safe and well tolerated.

3. Risk warning

1. Obtaining FDA approval for this new drug’s clinical trial application is a phased achievement of the company’s new drug research and development and an important reflection of the company’s new drug research and development capabilities. However, due to the characteristics of high technology, high risk, and high added value of pharmaceutical products, the cycle from drug development, clinical trials, approval to production is long, many links are involved, and the risks are high. There are many uncertainties in drug review and approval time, approval results and subsequent research processes, research results, and future product market competition. Investors are kindly requested to make prudent decisions and pay attention to preventing investment risks.

2. According to drug research and development experience, there are certain risks in clinical trial research. The progress and results of clinical trials are easily affected by (including but not limited to) trial protocols, subject recruitment, safety and effectiveness of clinical trials, etc., and the research and development situation is highly uncertain.

The company will actively promote the research and development and registration progress of the above-mentioned drugs and fulfill its information disclosure obligations in accordance with the law.

Announcement is hereby made.

Board of Directors of Yuekang Pharmaceutical Group Co., Ltd.

March 25, 2026