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SUZHOU, China, Oct. 19, 2025 /PRNewswire/ — CStone Pharmaceuticals (“CStone,” HKEX: 2616),  an innovation-driven biopharmaceutical company focused on the research and development of therapies for oncology, autoimmune/inflammation, and other key disease areas, today announced the first disclosure of preliminary Phase I data for CS2009 (a PD-1/VEGF/CTLA-4 trispecific antibody) and the Phase Ib study design for CS5001 (a ROR1-targeted Antibody-Drug Conjugate [ADC]) at the 2025 European Society for Medical Oncology (ESMO) Annual Congress.

Key Highlights of CS2009 Poster Presentation:

This also represents the first known clinical data publication of a PD-1/VEGF/CTLA-4 trispecific antibody to date.

CS2009-101 is a multi-regional phase Ⅰ study currently ongoing in Australia and China. The study evaluates the safety, tolerability, pharmacokinetics (PK)/ pharmacodynamics (PD), and antitumor activity of CS2009 in patients with advanced solid tumors.

Patients baseline characteristics:

1. As of the data cutoff date, 72 patients with advanced solid tumors treated across 6 dose levels (DL1-6, 1-45 mg/kg); 72.2% remain on treatment.
2. Heavily pretreated population: over 51% received prior immuno-oncology (IO) therapies. Median follow-up: only 1.9 months (range 0.1-6.7 months) at data cutoff.

Favorable safety and tolerability:

1. Dose escalation completed with no dose-limiting toxicity (DLT) reported; maximum tolerated dose (MTD) not reached.
2. No Grade 4 or 5 treatment-related adverse event (TRAE) observed. Incidence of Grade ≥3 TRAEs, immune-related AEs (irAEs), and VEGF-related TRAEs was 13.9%, 4.2%, and 2.8%, respectively.
3. Only 1 treatment-emergent adverse event (TEAE) leading to drug permanent discontinuation observed (at DL4 [20 mg/kg]; 1.4% incidence).

Promising antitumor activity and high disease control rate (DCR):

CS2009 demonstrated encouraging anti-tumor activities across tumor types. As of the cutoff date, the overall follow-up duration remained limited, particularly in higher-dose cohorts where the majority patients had yet to reach the protocol-specified time point of post-baseline tumor assessment:

1. 49/72 patients underwent at least one post-baseline tumor assessment by data cutoff.
2. Despite limited follow-up duration, anti-tumor activity was observed across all dose levels with dose-dependent uptrend:
   • Among all 49 evaluable patients, overall response rate (ORR) was 12.2%; DCR was 71.4%. Efficacy data remains immature; with additional follow-up beyond the poster data cutoff, ORR was further improved to 14.3%.
   • Higher ORR (25.0%) at tentative recommended Phase 2 dose (RP2D, 30 mg/kg) and higher dose.
3. Promising efficacy signals were observed across multiple tumor types within the short follow-up period:
   • Non-Small Cell Lung Cancer (NSCLC): ORR: 11.8%, DCR: 82.4%; Post-ESMO update: stable disease (SD)-to-partial response (PR) conversion observed, ORR further elevated to 17.6%; In AGA-negative subgroup, ORR reached 25%;
   • Ovarian Cancer (OC): ORR: 16.7%, DCR: 66.7%;
   • Triple-Negative Breast Cancer (TNBC): ORR: 25.0%, DCR: 75.0%;
   • Non–Clear Cell Renal Cell Carcinoma (nccRCC): ORR: 33.3%, DCR: 100.0%;
   • Soft Tissue Sarcoma (STS): ORR: 11.1%, DCR: 66.7%.

Favorable PK and PD profiles:

1. Linear PK with half-life of 6-8 days supported every-three-week (Q3W) dosing, with no significant accumulation observed at cycle 3.
2. PD profile demonstrated saturated receptor occupancy and robust T-cell activation/proliferation confirming PD-1/CTLA-4 blockade and deep and sustained VEGFA neutralization.
   • Receptor occupancy of PD-1/CTLA-4 on peripheral T cells reached saturation throughout dosing interval at doses ≥20 mg/kg.
   • On cycle 1 day 8, CS2009 induced notable, dose-dependent upregulation of Ki67 (proliferation due to PD-1 and CTLA-4 blockade) and ICOS (activation due to CTLA-4 blockade) expression on both CD4+ and CD8+ T cells, collectively demonstrating effective PD-1 and CTLA-4 inhibition.
   • Serum-free VEGFA reduced deeply and rapidly across all dose levels, and the effect sustained throughout dose intervals.

CStone has initiated Phase Ⅱ dose expansion study in first-line patients with selected tum or  types for dose optimization and to generate data supporting registration trials in first-line NSCLC and other tumors as monotherapy or in combination therapies.

CS2009 Data Review Conference Call:

CStone will host an investor meeting to discuss presented data and future clinical development plan. The Company cordially invites all investors to attend this conference call.

Chinese-language session:

• Date & Time: Monday, October 20, 2025, at 2:00 p.m. (Beijing Time)/2:00 a.m. (US Eastern Time)
• Registration Link: Registration is required, please sign up via the link: https://s.comein.cn/iq2y9krs

English-language session:

Key Highlights of CS5001 ePoster Presentation:

1. CS5001 phase Ib study aims to determine the RP2D and further evaluate the safety, tolerability, PK, and efficacy of CS5001 as a monotherapy and in combination with systemic therapies in selected tumor types.
2. In monotherapy cohorts, Cohorts A-D enroll patients with chronic lymphocytic leukemia and other B-cell lymphomas, and Cohort I enrolls patients with ROR1-positive solid tumors. In combination therapy cohorts (E-H), CS5001 will be administered with standard systemic therapies (R-GemOx, R2 or R-CHOP) or with sugemalimab (an anti-PD-L1 monoclonal antibody). 
3. Patient enrollment for CS5001 Phase Ib study commenced in December 2024 and is currently advancing smoothly at 30 sites across Australia, the United States, and China.

About CStone

CStone (HKEX: 2616), established in late 2015, is an innovation-driven biopharmaceutical company focused on the research and development of therapies for oncology, autoimmune/inflammation, and other key disease areas. 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.

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.

SOURCE CStone Pharmaceuticals

–          The 12-week U.S. Phase IIa study is evaluating the efficacy, safety and tolerability of the once-monthly subcutaneous (SQ) depot formulation (treatment formulation) of small molecule GLP-1 receptor (GLP-1R) agonist ASC30 in 65 participants with obesity or overweight.

–          The ultra-long-acting SQ depot treatment formulation of small molecule ASC30 demonstrated a 46-day observed half-life in participants with obesity in the Phase Ib study, supporting once-monthly administration.

–          Topline data from the 12-week Phase IIa study of ASC30 once-monthly SQ depot treatment formulation are expected in the first quarter of 2026.

–          The Company will host a conference call in Mandarin today at 10:00 a.m. China Standard Time. 

HONG KONG, Oct. 19, 2025 /PRNewswire/ — Ascletis Pharma Inc. (HKEX: 1672, “Ascletis”) announces the recent completion of enrollment in the U.S. Phase IIa study for its once-monthly subcutaneous (SQ) depot formulation (treatment formulation) of small molecule GLP-1 receptor (GLP-1R) agonist ASC30 for the treatment of obesity (NCT06679959). All 65 participants are obese or overweight with at least one weight-related comorbidity.

The Phase IIa study of ASC30 once-monthly SQ depot treatment formulation is a 12-week, randomized, double-blind, placebo-controlled and multi-center study conducted in the U.S. to evaluate the safety, tolerability and efficacy in participants with obesity (body mass index (BMI) ≥ 30 kg/m²) or overweight (BMI ≥ 27 kg/m² but < 30 kg/m²) with at least one weight-related comorbidity. The study consists of three cohorts of different doses, with a total of 65 participants. Topline data are expected in the first quarter of 2026.

The ultra-long-acting SQ depot treatment formulation of small molecule ASC30 demonstrated a 46-day observed half-life (as measured by time to 50% C_max) in participants with obesity in the Phase Ib study (NCT06679959), supporting once-monthly administration. ASC30 treatment formulation’s terminal half-life was 36 days.

Furthermore, the U.S. Phase Ib single ascending dose (SAD) study demonstrated that compared to the trough concentration of ASC30 at Day 29, the ultra-long-acting SQ depot treatment formulation showed a peak-to-trough ratio of approximately 1.5 to 1. The proprietary SQ depot slow-release treatment formulation of ASC30 was developed from Ascletis’ Ultra-Long-Acting Platform (ULAP). Ascletis’ ULAP technology does not have the limitations of albumin-dependent half-life extension technology, currently being applied to many peptide drugs and candidates, which limits half-life extension to the half-life of albumin (approximately 20 days).

“Completing enrollment in this study is an important milestone, marking significant progress in our development of this innovative therapy,” said Jinzi Jason Wu, Ph.D., Founder, Chairman and CEO of Ascletis, “Ascletis’ proprietary ultra-long-acting SQ depot treatment formulation of ASC30, with its 46-day observed half-life and favorable peak-to-trough ratio of approximately 1.5 to 1, demonstrated the potential to become a once-monthly treatment option for obesity. We are looking forward to topline data from this Phase IIa study in the first quarter of 2026.”

ASC30 was discovered and developed in-house at Ascletis as a first and only investigational small molecule GLP-1R biased agonist designed to be administered once daily orally and once monthly to once quarterly subcutaneously as a treatment therapy and a maintenance therapy for chronic weight management.

Conference Call

Ascletis will host a conference call in Mandarin today, October 20, 2025 at 10:00 a.m. China Standard Time. A live webcast of the call will be available via Tecent Meeting/ VooV Meeting, with the Meeting ID: 216-282-339, or access links of:

Chinese Mainland ^[1]: https://meeting.tencent.com/dm/8LbPT9Fs9HoW; or
International: https://voovmeeting.com/dm/8LbPT9Fs9HoW.

About ASC30

ASC30 is an investigational GLP-1R biased small molecule agonist and has unique and differentiated properties that enable the same small molecule for both oral tablet and subcutaneous injection administrations. ASC30 is a new chemical entity (NCE), with U.S. and global compound patent protection until 2044 without patent extensions. 

About Ascletis Pharma Inc.

Ascletis Pharma Inc. is a fully integrated biotechnology company focused on the development and commercialization of potential best-in-class and first-in-class therapeutics to treat metabolic diseases. Utilizing its proprietary Artificial Intelligence-Assisted Structure-Based Drug Discovery (AISBDD) and Ultra-Long-Acting Platform (ULAP) technologies, Ascletis has developed multiple drug candidates in-house, including its lead program, ASC30, a small molecule GLP-1R agonist designed to be administered once daily orally and once monthly to once quarterly subcutaneously as a treatment therapy and a maintenance therapy for chronic weight management. Ascletis is listed on the Hong Kong Stock Exchange (1672.HK).

For more information, please visit www.ascletis.com.

Contact：

Peter Vozzo
ICR Healthcare
443-231-0505 (U.S.)
[email protected]

Ascletis Pharma Inc. PR and IR teams
+86-181-0650-9129 (China)
[email protected]
[email protected]

SOURCE Ascletis Pharma Inc.