CS2009 Achieved Key Clinical Validations for Efficacy and Safety

As of August 2026, updated data further confirmed the favorable safety profile of CS2009 and demonstrated strengthened efficacy across multiple key cohorts compared with the data presented at ASCO in May 2026. With expanded patient enrollment and longer follow-up, improvements were observed in both the objective response rate $(ORR)$ and duration of response (DOR):

Compelling monotherapy efficacy in first-line non-small cell lung cancer (NSCLC)

   -- At the 30 mg/kg dose level, CS2009 achieved an ORR of 100% and a disease 
      control rate (DCR) of 100% in patients with PD-L1 TPS >=50%. In the 
      broader PD--L1 TPS >=1% population, the ORR was 70.8% and DCR was 91.7%. 

Monotherapy efficacy in Immunotherapy (IO)-pretreated NSCLC and IO-nonresponsive "cold tumors" further validates CTLA-4 activity and efficacy.

   -- In second-line NSCLC patients (all previously treated with IO plus 
      chemotherapy), CS2009 monotherapy (30 mg/kg dose level) yielded an ORR of 
      38.5% and a DCR of 84.6%; 
 
   -- In patients with heavily pretreated metastatic colorectal cancer (mCRC), 
      CS2009 monotherapy (30 mg/kg dose level) achieved an ORR of 20% and a DCR 
      of 93.3%; 
 
   -- In patients with heavily pretreated soft tissue sarcoma (STS) and 
      non-clear cell renal cell carcinoma (nccRCC), CS2009 monotherapy 
      delivered ORR of 38.5% and 42.9%, respectively. 

CStone will present additional more mature Phase I/II clinical data for CS2009 in patients with advanced NSCLC and mCRC via two rapid oral presentations at ESMO 2026 in October. The Company also expects to reach consensus with global regulatory authorities including the U.S. Food and Drug Administration (FDA) and the Center for Drug Evaluation $(CDE)$ of China National Medical Products Administration (NMPA), on the global Phase III registrational trial protocol in the fourth quarter of 2026.

Pralsetinib Delivers Strong Sales Growth

Following its effective inclusion in the National Reimbursement Drug List (NRDL) on January 1, 2026, pralsetinib's in-market sales volume increased by almost 500% year-over-year in the seven--month period ending July 2026.

Solid Cash Position

As of June 30, 2026, cash and cash equivalents and time deposits totaled RMB1,560.2 million.

SUZHOU, China, Aug. 31, 2026 /PRNewswire/ -- CStone Pharmaceuticals ("CStone," HKEX: 2616), an innovation-driven biopharmaceutical company focused on the research and development of therapies for oncology, immunology, inflammation, and other key disease areas, today announced its 2026 interim results and recent business highlights.

Dr. Jason Yang, CEO, President of R&D, and Executive Director at CStone, commented, "In the first half of 2026, CStone entered a pivotal stage of transition from innovation-driven accumulation to global value realization.

Our lead asset, CS2009, continues to advance rapidly through global clinical development. To date, we have accumulated clinical data from more than 300 patients, consistently demonstrating three key clinical validations: first, proof of safety; second, multidimensional confirmation of CTLA--4 target activity and efficacy, evidenced by pharmacodynamic biomarkers and clinical activity in "cold tumors" and IO--pretreated NSCLC; and third, broad--spectrum and highly competitive antitumor efficacy across multiple tumor types. The most recent data show that CS2009's antitumor activity continues to deepen and strengthen with longer follow-up, exhibiting particularly competitive efficacy and a well-tolerated safety profile in key patient populations, including NSCLC and mCRC. These robust data provide strong support for the upcoming global Phase III registrational trials. We look forward to presenting additional more mature clinical data on CS2009 in oral presentations at the ESMO Congress this October.

Beyond CS2009, other Pipeline 2.0 candidates are also progressing steadily toward clinical stage. CS5007, built on our proprietary ADC platform, has initiated a global Phase I clinical trial in both China and Australia. In addition, more than ten early-stage programs spanning next-generation ADCs, immunology & inflammation and other areas are advancing smoothly. The successive entry of these differentiated innovative assets into clinical development will serve as a critical driver for the Company's sustained growth and global expansion.

On the commercial front, our three key products, sugemalimab, pralsetinib, and avapritinib, continued to achieve breakthroughs across domestic and international markets, contributing significant momentum to revenue growth. Notably, following pralsetinib's first-time inclusion in the NRDL earlier this year, its in-market sales volume increased by almost 500% year-over-year during the first seven months of 2026, making it the primary driver of the Company's revenue growth in the first half of 2026.

Looking ahead, CStone will focus on advancing the clinical value of its Pipeline 2.0 assets and actively pursue global partnerships to accelerate their development. Concurrently, the Company will continue to maximize the commercial potential of its marketed products through strategic partnerships and resource integration. Our goal is to foster a sustainable growth model where R&D and commercialization reinforce each other, creating a virtuous cycle between innovation and business operations."

Clinical Stage Core Asset

CS2009, PD-1/VEGF/CTLA-4 trispecific antibody

- Accelerating global clinical development toward Phase III registrational trials by year end

The ongoing global Phase I/II trial has enrolled more than 300 patients across China and Australia, with U.S. Investigational New Drug (IND) clearance obtained in February 2026.

CStone plans to initiate the first wave of global Phase III multi-regional clinical trials (MRCTs) for CS2009 by the end of 2026. Planned registrational studies include first-line non-small cell lung cancer (NSCLC) in combination with chemotherapy (versus pembrolizumab plus chemotherapy), and first-line mCRC in combination with chemotherapy (versus bevacizumab plus chemotherapy), with additional registrational studies planned for 2027 and following years.

- CS2009 validates its potential as a next-generation I/O backbone

At the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, CStone presented comprehensive Phase I/II data from the ongoing global multicenter trial. As of the data cutoff date of August 2026, updated monotherapy efficacy data from the ongoing global Phase I/II trial of CS2009, reflecting a longer follow-up and larger sample size than the ASCO 2026 presentation continued to demonstrate robust and deepening antitumor activity across multiple tumor types. Three important key clinical validations are achieved from over 300 patient data:

   -- Proof of safety 

Across all dose levels, no dose-limiting toxicities (DLTs) were observed, and the maximum tolerated dose $(MTD)$ was not reached. In the ASCO 2026, the incidence of Grade SHY3 treatment-related adverse events (TRAEs) and immune-related adverse events (irAEs) were 24.6% and 12.7%, respectively. Notably, the incidence of Grade SHY3 VEGF-related TRAEs was only 5.1%. No excessive toxicities typically associated with CTLA-4/PD-(L)1 combinations were observed. As of August 2026, the safety profile of CS2009 remained consistent with that presented at the 2026 ASCO Annual Meeting, with no new safety signals identified.

   -- Proof of CTLA-4 activities and efficacy 

Dose-dependent upregulation of ICOS on CD4+ T cells was observed as a pharmacodynamic biomarker of CTLA-4 blockade. Activity was also seen in "cold tumor" not sensitive to PD-(L)1 mAb:

          -- Later-line monotherapy for mCRC (30 mg/kg): the objective response 
             rate (ORR) was 20.0% (3/15) and the disease control rate (DCR) was 
             93.3% (14/15). 
 
          -- Later-line monotherapy for soft-tissue sarcoma (STS): the ORR was 
             38.5% (5/13) and the DCR was 69.2% (9/13). Later-line monotherapy 
             for non-clear cell renal cell carcinoma (nccRCC): the ORR was 
             42.9% (3/7) and the DCR was 100.0% (7/7). 
 
          -- Promising anti-tumor activity in later-line post immuno-oncology 
             (IO) NSCLC monotherapy: ORR was 23.8% (5/21), DCR was 61.9% 
             (13/21). Among patients who had previously received immunotherapy 
             plus platinum-based chemotherapy (n=13), ORR was 38.5% (5/13) and 
             DCR was 84.6% (11/13). 
   -- Proof of broad efficacy 

Monotherapy and chemo-combination activity in first-line and later-line NSCLC:

          -- First-line NSCLC monotherapy (PD-L1 tumor proportion score 
             [TPS]SHY >=1%; enrollment completed): ORR of 61.7% (29/47) and DCR 
             of 93.6% (44/47), including ORR of 70.8% (17/24), DCR 91.7% 
             (22/24) in patients treated at 30 mg/kg; in the PD-L1 TPS >=SHY50% 
             group (n=24), ORR was 83.3% (20/24) and DCR was 95.8% (23/24) 
             (versus ORR of 81.3% [13/16] at the 2026 ASCO cutoff), including 
             ORR of 100.0% (11/11) and DCR of 100.0% (11/11) in patients 
             treated at 30 mg/kg. After median follow up of 6 months, median 
             progression-free survival (PFS) and DOR have not been reached. 
 
          -- Second-line or later NSCLC monotherapy (30 mg/kg): ORR of 28.0% 
             (7/25) and DCR of 60.0% (15/25), with a 6-month DOR rate of 83.3% 
             (versus ORR of 24.0% and a 6-month DOR rate of 80.0% at the 2026 
             ASCO cutoff). Across all evaluated dose levels (n=54), ORR was 
             16.7% (9/54) and DCR was 68.5% (37/54), with a 6-month DOR rate of 
             87.5% (versus 85.7% at the 2026 ASCO cutoff). 
 
          -- Later-line NSCLC (second/third-line combination therapy, n=6): ORR 
             of 66.7% (4/6), DCR of 100.0% (6/6). Data are as of the 2026 ASCO