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SHANGHAI, October 27, 2026 — Hansoh Pharmaceutical Group Co., Ltd. (Hansoh Pharma, 03692.HK) announced that the primary results from the Phase 3 ARTEMIS-011 study of risvutatug rezetecan (“Ris-Rez”) (HS-20093/GSK5764227) were presented orally as a Late-Breaking Abstract (LBA) at the Presidential Symposium of the 2026 European Society for Medical Oncology (ESMO) Congress, held in Madrid, Spain, from October 23 to 27.

The study evaluated Ris-Rez versus gemcitabine plus docetaxel (GD) in heavily pretreated patients with R/R osteosarcoma following failure of at least two prior lines of therapy. At the prespecified analysis, the study met its primary endpoint of PFS as assessed by blinded independent central review (BICR), demonstrating a statistically significant and clinically meaningful improvement, with a 67% reduction in the risk of disease progression or death.

Ris-Rez is a proprietary B7-H3—directed antibody-drug conjugate (ADC) independently developed by Hansoh Pharma. It consists of a fully human anti-B7-H3 IgG1 monoclonal antibody conjugated to a topoisomerase I inhibitor (TOP1i) payload (rezetecan) through a cleavable linker. In China, Ris-Rez is currently being evaluated in pivotal Phase 3 studies in non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), osteosarcoma and oesophageal cancer. On September 24, 2026, the National Medical Products Administration (NMPA) of China accepted the Biologics License Application (No. CXSS2600155) for Ris-Rez in the treatment of osteosarcoma and granted it Priority Review status. To date, Ris-Rez has received 12 regulatory designations, including Breakthrough Therapy Designation and Orphan Drug Designation, across China, the United States, Japan and Europe.

Primary results from ARTEMIS-011 presented at ESMO 2026 showed that Ris-Rez significantly improved PFS in patients with R/R osteosarcoma compared with GD -- an improvement that was both statistically significant and clinically meaningful. This is the first positive Phase 3 study in R/R osteosarcoma in nearly 30 years. Ris-Rez is also the first and only B7-H3—directed ADC to demonstrate a statistically significant benefit across multiple tumour types. With positive Phase 3 results now achieved, Ris-Rez has reached a key milestone in the clinical development of B7-H3—directed ADCs, advancing from clinical study towards two regulatory submissions in China. Hansoh Pharma is continuing to advance the development of Ris-Rez across multiple tumour types and treatment lines, fully exploring the therapeutic potential of the B7-H3 ADC and bringing China’s innovations to benefit more patients. GSK holds exclusive rights to develop and commercialise Ris-Rez outside mainland China, Hong Kong, Macau and Taiwan, and is advancing a broad global clinical development programme across lung cancer, prostate cancer and other solid tumours.

LBA Presentation Details:

Presentation Title: Risvutatug Rezetecan Versus Gemcitabine and Docetaxel in Heavily Pretreated Patients With Relapsed or Refractory Osteosarcoma: Primary Results From the Phase 3 ARTEMIS-011 Study

Session: Presidential Symposium III

Abstract No.: LBA9

Date/Time: Monday, October 26, 2026, 16:30–16:42 CET / UTC +1

Presenter: Prof. Lu Xie, Peking University People's Hospital

About the ARTEMIS-011 Study

ARTEMIS-011 is a multi-centre, open-label, randomised (2:1), controlled Phase 3 study in which 122 patients with R/R osteosarcoma after failure of at least two prior lines of therapy were randomised to receive risvutatug rezetecan (12.0 mg/kg IV once every three weeks) or gemcitabine plus docetaxel, with as of the data cutoff date of June 17, 2026 (median follow-up: 7.1 months).

Efficacy

Progression-free survival (BICR, primary endpoint): Median PFS was 5.5 months with Ris-Rez vs 1.4 months with gemcitabine plus docetaxel (HR=0.33; 95% CI: 0.20-0.55; p<0.0001), a 67% reduction in the risk of disease progression or death. Investigator-assessed PFS also showed a consistent benefit vs GD: median PFS was 5.6 months with Ris-Rez vs 1.0 months with GD (HR=0.30; 95% CI: 0.19-0.50; p<0.0001). Benefit was consistent across all prespecified subgroups, including age, sex, lung metastasis, baseline tumour burden, ECOG PS, and number of prior lines of therapy.

Response (BICR): ORR was 15% vs 2% and DCR was 76% vs 33%; median duration of response was 7.6 months with Ris-Rez. Investigator-assessed ORR, DCR and DOR were consistent with BICR-assessed results.

Overall survival: OS data were immature but suggested a numerical trend toward an OS benefit with Ris-Rez (median not reached in either arm; HR=0.51; 95% CI: 0.21-1.23).

Safety

Ris-Rez showed a manageable safety profile in this heavily pretreated population. The most common treatment-related adverse events (TRAEs) of any grade and of Grade ≥ 3 in both arms were haematological; no Grade 5 (fatal) event occurred in either arm. Grade ≥ 3 TRAEs occurred in 93% of patients with Ris-Rez and 83% with GD, and serious TRAEs in 64% versus 29%, which were predominantly haematologic. Treatment-related interstitial lung disease (ILD) was observed in only 1 patient (Grade 2) in the Ris-Rez arm, and it resolved with supportive management. Longer treatment duration was observed with Ris-Rez (median 4.5 vs 1.5 months).

These results suggest that Ris-Rez represents a promising potential treatment option for patients with previously-treated R/R osteosarcoma

About Osteosarcoma

Osteosarcoma is the most common malignant bone tumour, accounting for 35% of all malignant bone tumours, and has been included in the Second Batch of Rare Disease Catalogue issued by the National Health Commission of China ^[1]. The median age at onset of osteosarcoma is 20 years, and it is the most common primary malignant bone tumour in children and adolescents. Approximately 20%-30% of patients with localised (non-metastatic) osteosarcoma and 80% of patients with metastatic osteosarcoma will progress to an advanced stage (relapse or metastasis), whereas the 5-year survival rate of patients with advanced osteosarcoma is only about 20% ^[2,3]. Globally, patients with relapsed or refractory osteosarcoma after first-line chemotherapy have limited treatment options and lack a clear standard of care ^[4,5]. For patients whose osteosarcoma progresses after two or more prior lines therapy, treatment options are even more limited, representing a substantial unmet clinical need.

References

[1] National Health Commission of the People's Republic of China. Second Batch of Rare Disease Catalogue, Document No. 26 (2023), September 18, 2023.

[2] Durfee RA, Mohammed M, Luu HH. Review of Osteosarcoma and Current Management. Rheumatol Ther. 2016 Dec;3(2):221-243.

[3] Meltzer PS, Helman LJ. New Horizons in the Treatment of Osteosarcoma. N Engl J Med. 2021;385(22):2066-2076.

[4] National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®): Bone Cancer. July 21, 2026. Version 1.2027.

[5] Chinese Society of Clinical Oncology (CSCO). CSCO Clinical Practice Guidelines: Bone and Soft Tissue Cancer (2025).