SHENZHEN, China, March 13, 2026 — Shenzhen Chipscreen Biosciences Co., Ltd. ("Chipscreen Biosciences", Stock Code: 688321.SH) today announced that it has received approval from the National Medical Products Administration (NMPA) for the Investigational New Drug (IND) application of its Class 1 novel drug, CS08399 tablets, a brain-penetrant PRMT5 inhibitor for the treatment of the treatment of solid tumors and lymphomas with methylthioadenosine phosphorylase (MTAP) deficiency.. The application was submitted by the company's wholly-owned subsidiary, Chengdu Chipscreen Pharmaceutical Co., Ltd.

Cancer continues to be a leading cause of mortality worldwide, presenting persistent and critical clinical challenges. While therapeutic options have advanced significantly, a substantial unmet medical need remains for patients with advanced-stage diseases. The development of novel drugs targeting new mechanisms is therefore critical to improve patient outcomes. It is estimated that approximately 10%-15% of tumors carry a Methylthioadenosine Phosphorylase (MTAP) gene deletion, which is associated with poorer prognosis and limited response to current standard therapies, including immunotherapy.

CS08399 is a brain-penetrant, MTA-cooperative small molecule inhibitor of Protein Arginine Methyltransferase 5 (PRMT5), entirely discovered and developed by Chipscreen Biosciences leveraging its proprietary "AI + chemical genomics" core technology platform. The drug is designed to selectively target MTAP-deficient tumor cells through a precise mechanism. In these cells, the loss of MTAP function leads to intracellular accumulation of methylthioadenosine (MTA), an endogeneous PRMT5 inhibitor. CS08399 specifically binds to and stabilizes the PRMT5-MTA complex, potently inhibiting PRMT5 enzymatic activity. This action effectively reduces levels of PRMT5-mediated symmetric dimethylarginine (SDMA), leading to selective cell cycle arrest and apoptosis in MTAP-deficient tumors while sparing normal cells, indicating a favorable therapeutic window. Furthermore, by inhibiting PRMT5, a key epigenetic regulator, CS08399 may modulate the tumor microenvironment, offering potential to address challenges like drug resistance and immune evasion. Currently, no therapies targeting this specific mechanism have been approved for marketing worldwide.

Comprehensive preclinical studies have demonstrated that CS08399 possesses promising pharmacodynamic activity, desirable pharmacokinetic properties, and a good safety profile. The drug holds potential not only as a monotherapy but also in combination regimens. For instance, it may offer new hope for MTAP-deficient patients who also harbor co-occurring driver mutations like EGFR or KRAS, or for those who have developed resistance to prior treatments. Looking ahead, CS08399, either alone or in combination with other anti-tumor agents, is poised to provide a differentiated and innovative treatment strategy for a broad range of cancer patients, marking a significant step forward in targeted oncology therapeutics.