Polaris Pharmaceuticals Voluntarily Withdraws US FDA Approval Application for Mesothelioma Drug

Announcement Date: 2025/05/25 Company Code: 6550 Company Name: Polaris Pharmaceuticals (KY)

Subject: The company plans to voluntarily withdraw its Biological License Application (BLA) for the use of Pegargiminase (ADI-PEG 20) in treating malignant pleural mesothelioma submitted to the US FDA.

1. Product Details: On November 16, 2023 (US time), the company submitted the BLA for Pegargiminase (ADI-PEG 20) to the US FDA for the treatment of malignant pleural mesothelioma (MPM) via rolling submission. The application entered the formal review phase in August 2025. During the review, the company maintained ongoing communication with the FDA regarding review requirements, data, and regulatory matters. After a comprehensive assessment of the current development timeline, product lifecycle management, global market presence, and future commercialization strategies, the company plans to withdraw this BLA application to preserve overall flexibility for future applications and development. This decision was made after careful review of operational strategies and long-term commercialization plans. Polaris Pharmaceuticals will continue to evaluate the future direction of this indication, considering the content of communications with the FDA and aligning it with future development strategies for ADI-PEG 20.

2. Product mass production date: N/A

3. Impact on company finances and operations: This case is an adjustment to the application process based on the company's overall research and development and regulatory strategy. The company will proceed with the withdrawal process according to relevant regulations and FDA procedures and will continue to evaluate the feasibility of Pegargiminase (ADI-PEG 20) for other indications and subsequent development plans. There is no major impact on the company's overall operations or shareholder interests.

4. Other disclosures: (I) Drug name or code: Pegargiminase (ADI-PEG 20). (II) Usage: Innovative arginine-deprivation drug. The original application was for treating malignant pleural mesothelioma. (III) Current R&D phase: Following the board's decision, the company will complete the withdrawal process in accordance with FDA regulations. (IV) Accumulated R&D investment: Currently undisclosed, considering future marketing strategies, international cooperation, and shareholder interests. (V) Market conditions: Malignant pleural mesothelioma is highly aggressive and challenging to treat, with limited therapeutic options. ADI-PEG 20 is a metabolic therapy that targets the arginine metabolism weakness of cancer cells, operating via a different mechanism of action than conventional therapies.

(Disclaimer: Drug development involves long timelines, high investment, and uncertain regulatory outcomes. Clinical trial results do not guarantee future commercial success. Investors should judge carefully.)