Malignant perivascular epithelioid cell tumor (PEComa) is a relatively rare mesenchymal tumor composed of perivascular epithelioid cells with distinctive histological and immunohistochemical features . This tumor is typically large, with marked nuclear atypia, frequent mitotic figures , tumor necrosis, and invasive growth, exhibiting an aggressive clinical course. Approximately 50% of patients with malignant PEComa are diagnosed at an advanced stage, often with metastasis, resulting in a poor prognosis.On June 3, 2026, according to the latest , the sirolimus for injection (albumin-bound) submitted by CSPC Ouyi Pharmaceutical Co., Ltd. is proposed to be included in the priority review list for the treatment of malignant perivascular epithelioid cell tumor (PEComa). According to a press release from CSPC Pharmaceutical Group, Sirolimus for Injection ( Albumin -Bound ) (HB1901) is a sirolimus albumin-bound nanoparticle suspension for injection. Its active pharmaceutical ingredient (API) is sirolimus, and it is a modified new drug that has not been marketed in China or abroad.HB1901, as a new dosage form (including a new drug delivery system) and/or a new route of administration containing a known active ingredient, is classified as a Class 2.2 new drug in the chemical drug registration category according to the "Drug Registration Management Measures".Sirolimus has poor water solubility, making it difficult to deliver effectively, which limits its application in the field of anti-tumor therapy. HB1901 is an injectable formulation developed by our group using innovative technology to encapsulate sirolimus in human serum albumin. It is also the first intravenously administered sirolimus formulation to obtain clinical approval in China.This achievement enables the Group to deliver sirolimus via injection, effectively overcoming the shortcomings of traditional oral formulations, such as low bioavailability and the inability to deliver sufficient drug concentrations to the target site, thereby expanding the application of this drug in the field of anti-tumor therapy. Compared with marketed mTOR inhibitor tablets and oral suspensions, HB1901 is expected to significantly improve the bioavailability of sirolimus and reduce gastrointestinal toxicity.On April 20, 2026, CSPC Pharmaceutical Group officially announced that its subsidiary, CSPC Zhongqi Pharmaceutical Technology (Shijiazhuang) Co., Ltd., had successfully achieved its pre-specified primary efficacy endpoint in a Phase Ib / III clinical trial ( protocol number: HB 1901-004 ) for the treatment of advanced malignant perivascular epithelioid cell tumor ( PEComa ) . The study results demonstrated both statistically significant differences and clear clinical benefits. HB 1901 exhibited excellent efficacy and is expected to fill the treatment gap , becoming the first standard treatment for advanced malignant PEComa in the country.HB1901-004 is a Phase Ib/III clinical trial designed to evaluate the safety and efficacy of injectable sirolimus (albumin-bound) in patients with advanced malignant PEComa. The core Phase III clinical trial, conducted in a head-to-head controlled, investigator-selective protocol, comprehensively validated the combined advantages of HB1901 over existing conventional treatments in terms of antitumor efficacy, clinical benefit, and safety and tolerability. This fully solidifies its clinical application value for rare and refractory tumors, providing a new and highly effective treatment option for patients with advanced malignant PEComa.It is reported that in February 2025, HB1901 received Breakthrough Therapy Designation from the National Medical Products Administration (NMPA). Currently, multiple clinical trials exploring the efficacy and safety of injectable sirolimus (albumin-bound) in combination with different drugs in various tumor types are progressing steadily.Perivascular epithelioid cell tumor (PEComa) is a rare type of mesenchymal tumor that can occur in multiple organs, including the uterus, kidneys, liver, and lungs. Approximately 50% of patients with malignant PEComa are diagnosed at an advanced stage, often with distant metastases, resulting in a poor prognosis. Currently, there is no universally accepted standardized treatment plan in China for advanced patients with incomplete tumor resection, postoperative recurrence, or metastasis, leading to a lack of clinical treatment options and a significant unmet need for effective treatment.The inclusion of sirolimus for injection (albumin-bound) in the priority review list will undoubtedly accelerate its market launch in China.

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