Suzhou, China, May 7, 2025 – CStone Pharmaceuticals (“CStone”, HKEX: 2616), an innovation-driven biopharmaceutical company focused on anti-cancer therapies, announced today that a poster presentation of preclinical data of CS5005 (SSTR2 antibody drug conjugate [ADC]), a key asset in CStone Pipeline 2.0, has been delivered at the 2025 American Association for Cancer Research (AACR) Annual Meeting.
Somatostatin receptor 2 (SSTR2) is a G protein-coupled receptor (GPCR) that is overexpressed in various solid tumors, including neuroendocrine tumors (NETs), neuroendocrine carcinomas (NECs), and small cell lung cancer (SCLC). Due to its tumor-selective expression profile, SSTR2 has emerged as a promising target in the field of precision oncology.
CS5005 is a first-in-class, SSTR2-targeting ADC, composed of CStone's proprietary anti-SSTR2 antibody with high affinity and selectivity, hydrophilic β-glucuronide linker, and potent topoisomerase I inhibitor, Exatecan. In preclinical studies, CS5005 demonstrated potent, antigen-dependent tumor growth inhibition that was not affected by co-administration with SSA-derived therapies. Additionally, CS5005 exhibited superior stability, monoclonal antibody-like pharmacokinetic (PK) properties, and favorable tolerability in preliminary non-human primate toxicity studies.
Key Highlights:
1. CS5005 demonstrated high affinity to SSTR2-positive cell lines and induced high-rate internalization on tumor cells.
2. CS5005 exhibited cross-reactivity with SSTR2-expressing cells in non-human primates and demonstrated selective binding to SSTR2 with minimal interaction with other SSTRs.
3. CS5005 demonstrated potent antigen-dependent cytotoxic activity against tumor cells in vitro and robust tumor-growth inhibition in CDX tumor model.
4. The antitumor activity of CS5005 (SSTR2-DXd) is not compromised by concomitant ligand-derived treatments (e.g., octreotide, Lutathera®), thereby avoiding drug-drug interference commonly observed with current anti-SSTR2 therapies.
5. CS5005 demonstrated superior in vitro stability due to its proprietary linker, outperforming ADCs conjugated with well-validated dipeptide and tetrapeptide linkers.
6. Superior pharmacokinetic (PK) properties of CS5005 in rodents.
7. Bioinformatics analysis of SCLC samples supports DLL3/SSTR2 dual targeting as a strategy to overcome tumor heterogeneity and expand the treatable patient population.
In summary, CS5005 is a first-in-class, SSTR2-targeting ADC designed to selectively eliminate SSTR2-positive tumors, including small cell lung cancer, neuroendocrine carcinoma, and neuroendocrine tumors. It is composed of CStone’s proprietary high-affinity, high-selectivity anti-SSTR2 antibody, CStone’s proprietary hydrophilic β-glucuronide linker, and potent TOP1 inhibitor payload. CS5005 has demonstrated robust antitumor activity in both in vitro and in vivo studies, supporting its progression toward IND submission and clinical development. The patent of de novo antibody backbone of CS5005 has been filed in the first half of 2024. CS5008, an SSTR2/DLL3 bispecific ADC is under development. By simultaneously targeting SSTR2 and DLL3 that frequently co-express in SCLC, NETs, NECs and others, CS5008 aims to overcome tumor heterogeneity, a challenge faced by mono-specific therapies.
Poster Information:
【Title】CS5005: A novel SSTR2-targeted antibody-drug conjugate (ADC) with robust anti-tumor activity in preclinical studies
【Session Title】Molecular, Preclinical, and Clinical Endocrinology
【Abstract Number】4751
【Date & Time】Tuesday, April 29, 2025, 9:00 AM - 12:00 PM ET
【Location】Poster Section 35, Board #18
About CStone
CStone (HKEX: 2616), established in late 2015, is an innovation-driven biopharmaceutical company focused on the research and development of anti-cancer therapies. Dedicated to addressing patients’ unmet medical needs in China and globally, the Company has made significant strides since its inception. To date, the Company has successfully launched 4 innovative drugs and secured approvals for 16 new drug applications covering 9 indications. The company’s pipeline is balanced by 16 promising candidates, featuring potentially first-in-class or best-in-class antibody-drug conjugates (ADCs), multispecific antibodies, immunotherapies and precision medicines. CStone also prides itself on a management team with comprehensive experiences and capabilities that span the entire drug development spectrum, from preclinical and translational research to clinical development, drug manufacturing, business development, and commercialization. For more information about CStone, please visit www.cstonepharma.com.
IR contact: ir@cstonepharma.com
PR contact: pr@cstonepharma.com
Forward-looking statements
The forward-looking statements made in this article only relate to events or information as of the date when the statements are made in this article. Except as required by law, we undertake no obligation to update or publicly revise any forward-looking statements, whether as a result of new information, future events or otherwise, after the date on which the statements are made or to reflect the occurrence of unanticipated events. You should read this article completely and with the understanding that our actual future results or performance may be materially different from what we expect. All statements in this article are made on the date of publication of this article and may change due to future developments.
Disclaimer: only for communication and scientific use by medical and health professionals, it is not intended for promotional purposes.
Your privacy is important for us. We use cookies to enhance your experience when visiting our websites: performance cookies show us how you use this website, functional cookies remember your preferences and targeting cookies help us to share content relevant to you. Select “Accept all” for giving your consent to all cookies or select “Reject all” for using only strictly necessary cookies.
