VOLUNTARY ANNOUNCEMENT - Phase Ib/III Clinical Study of Sirolimus for Injection (Albumin-Bound) (HB1901) for the Treatment of Advanced Malignant Perivascular Epithelioid Cell Tumour (PEComa) Meets Primary Endpoint

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CSPC PHARMACEUTICAL GROUP LIMITED (Incorporated in Hong Kong with limited liability) (Stock Code: 1093) ʮ ̡ VOLUNTARY ANNOUNCEMENT Phase Ib/III Clinical Study of Sirolimus for Injection (Alb umin-Bound) (HB1901) for the Treatment of Advanced Malignant Perivascular Epith elioid Cell Tumour (PEComa) Meets Primary Endpoint The Board of Directors (the ‘‘Board ’’) of CSPC Pharmaceutical Group Limited (the ‘‘Company ’’, together with its subsidiaries, the ‘‘Group ’’) is pleased to announce that the Phase Ib/III clinical study (Study Protocol No.: ‘‘HB1901-004 ’’) of Sirolimus for Injection (Albumin-bound) ( ‘‘HB1901 ’’), independently developed by the Company ’s subsidiary, CSPC Zhongqi Pharmaceutical Technology (Shijiazhuang) Co., Ltd., for the treatment of advanced mal ignant perivascular epithelioid cell tumour (‘‘PEComa ’’) has successfully met its pre-specified primary efficacy e ndpoint, with the study results demonstrating both statistically significant difference s and clear clinical benefits. HB1901 has showed excellent efficacy and is expected to fill the therapeutic g ap for this indication in China, potentially becoming the first standard treatment regimen for advanced malignant PEComa in the domestic market. Malignant PEComa is a relatively rare mesenchymal tumour co mposed of perivascular epithelioid cells with distinctive histological and immunohistochemical fe atures. These tumours are typically large in size, accompanied by marked nuclear atypia, readily identi fiable mitotic figures, tumour necrosis, and infiltrative growth, exhibiting an aggressive clinical co urse. Approximately 50% of patients with malignant PEComa are already at an advanced stage upon diagn osis, often complicated by metastasis, resulting in a poor prognosis. For patients with advanced ma lignant PEComa whose tumours cannot be completely resected, or who experience postoperative recu rrence and distant metastasis, there is currently no recognised standard treatment regimen in Chin a. Clinical therapeutic options remain scarce, representing a substantial and urgent unmet medica l need. – 1 – HB1901-004 is a Phase Ib/III clinical study designed to eval uate the safety and efficacy of Sirolimus for Injection (Albumin-bound) in patients with advanced ma lignant PEComa. Specifically, the pivotal Phase III clinical study, conducted in a head-to-head compa rison against the investigator ’s choice of therapy, comprehensively validated the overall advantage s of HB1901 over existing conventional treatments in terms of anti-tumour efficacy, clinical bene fit, and safety/tolerability profile. This fully solidifies its clinical application value for rare and refr actory tumours, offering a novel and highly effective treatment option for patients with advanced mali gnant PEComa. About Sirolimus for Injection (Albumin-bound) (HB1901) HB1901 is a sirolimus albumin-bound nanoparticle suspensi on for injection with sirolimus as its active pharmaceutical ingredient (API). It is a modified new drug n ot yet marketed domestically or overseas. As a preparation that contains a known active ingredient wit h a new dosage form (including a new drug delivery system) and/or a new route of administration, HB19 01 is classified as a Class 2.2 new drug under the registration classification of chemical drugs in accordance with the Measures for the Administration of Drug Registration. Sirolimus has poor water solubility and is difficult to deli ver effectively, which limits its application in the oncology field. HB1901 is an injectable formulation dev eloped by the Group using innovative technology to encapsulate sirolimus in human serum albumin . It is also the first intravenously administered sirolimus formulation to obtain clinical tri al approval in China. The Group has therefore successfully achieved the injectable delivery of sirolimu s, effectively overcoming the disadvantages of traditional oral formulations, such as low bioavailabilit y and inability to deliver sufficient drug concentrations to target sites, thereby expanding the appl ication of this drug in the oncology field. Compared with marketed tablet and oral suspension formulat ions of mTOR inhibitors, HB1901 is expected to significantly improve the bioavailability of s irolimus and reduce gastrointestinal toxicity. In February 2025, HB1901 was granted Breakthrough Therapy D esignation by the National Medical Products Administration (NMPA). Currently, multiple clin ical trials exploring the efficacy and safety of Sirolimus for Injection (Albumin-bound) in combination wi th different agents across various tumour types are steadily advancing. By order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 20 April 2026 As at the date of this announcement, the Board comprises Mr. C AI Dong Chen, Dr. CAI Lei, Mr. WEI Qingjie, Mr. ZHANG Cuilong, Mr. WANG Zhenguo, Mr. WANG Huaiy u, Dr. LI Chunlei, Dr. YAO Bing, Mr. CAI Xin, Mr. CHEN Weiping, Mr. QU Zhiyong and Mr. ZHANG Yiw ei as Executive Directors; and Mr. WANG Bo, Mr. CHEN Chuan, Prof. WANG Hongguang, Mr. AU Chun Kwok Alan, Mr. LAW Cheuk Kin Stephen and Ms. LI Quan as Independent Non-executive Dir ectors. – 2 –

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