2253 - Efficacy and Safety of Albumin-bound Docetaxel Plus Enlonstobart vs. Paclitaxel, Combined with Cisplatin and Concurrent Radiotherapy in Patients with Locally Advanced Unresectable Esophageal Squamous Carcinoma: Results from a Randomized Phase II Study
Presenter(s)
L. Wang1, Q. Wang2, R. Yu3, Y. Wang4, C. Yu5, C. Wang6, Y. Xu7, W. Huang8, L. Wang8, J. Yuan9, Y. Wang8, Y. Ma10, J. Yu1, and Q. S. Pang11; 1Shandong Cancer Hospital and Institute, Jinan, China, 2Sichuan Cancer Hospital and Institute, Chengdu, China, 3Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China, 4Chongqing University Cancer Hospital, Chongqing, China, 5Huai'an First People's Hospital, Huai'an, China, 6Harbin Medical University Cancer Hospital, Harbin, China, 7Zhejiang Cancer Hospital, Hangzhou, China, 8CSPC Pharmaceutical Group Limited, Beijing, China, 9CSPC Pharmaceutical Group Limited, Shijiazhuang, China, 10CSPC Pharmaceutical Group Limited, Wuhan, China, 11Tianjin Medical University Cancer Institute and Hospital, Tianjin, China
Purpose/Objective(s):
For unresectable locally advanced esophageal squamous cell carcinoma (LA-ESCC), paclitaxel plus cisplatin with concurrent radiotherapy (CCRT) is recommended first-line standard of care (SOC). Evidence shows adding PD-1 immunotherapy to this SOC can improve antitumor activity. HB1801 is albumin-bound docetaxel for injection and Enlonstobart is a fully humanized anti-PD-1 IgG4 monoclonal antibody. We hypothesize that HB1801 and Enlonstobart plus cisplatin with CCRT offers more efficacy than SOC alone. Here, we present preliminary efficacy and safety results from the phase II study (NCT06136988).Materials/Methods:
This phase II study was a randomized, open-label, multicenter, controlled trial. Eligible patients (18–75 years) had unresectable LA-ESCC suitable for definitive CCRT and Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0-1 (=7 days pre-dose). Stratified by ECOG PS (0 vs 1) and stage (II/III vs IV [IVa and IVb with supraclavicular lymph node metastasis (SLNM)]), patients were randomized 1:1 to Experimental or SOC group. In Experimental group, patients received two 3-week cycles of Enlonstobart 360 mg + HB1801 60 mg/m² (day 1) plus cisplatin 25 mg/m² (days 1–3), with CCRT (50.4 Gy/28 fractions (fx); 1.8 Gy/fx, 5 fx/week). Enlonstobart 360 mg continued every 3 weeks as maintenance. In SOC group, patients received two 3-week cycles of paclitaxel 135 mg/m² (day 1) plus cisplatin 25 mg/m² (days 1–3), with identical CCRT. Primary endpoint was progression-free survival (PFS).Results:
As of February 13, 2026 (data cut-off), 43 patients were enrolled (Experimental vs SOC group: 19 vs 24), with median age 62 vs 62 years, 94.7% vs 87.5% male, 68.4% vs 66.7% stage II/III disease, and 100% vs 91.7% SLNM. All treated patients (=1 dose) experienced treatment-emergent adverse event (TEAE). The incidence of grade =3 TEAEs was 72.2% in Experiment group vs 62.5% in SOC group. Most common grade =3 TEAEs (=10% in either group) were lymphopenia (50.0% vs 45.8%), leukopenia (27.8% vs 20.8%), anemia (5.6% vs 16.7%) and neutropenia (22.2% vs 12.5%). No unexpected serious TEAEs occurred. After a median follow-up of 11.7 months (IQR, 10.3-12.8), PFS events occurred in 21.1% (4/19) vs 41.7% (10/24). The median PFS was NR vs 8.71 months; 6- and 9-month PFS rates were 88.9% (95% CI, 62.4-97.1) vs 73.8% (95% CI, 50.7-87.3) and 76.9% (95% CI, 49.4-90.7) vs 47.4% (95% CI, 21.9-69.2), respectively. Median overall survival was not yet mature.Conclusion:
HB1801 and Enlonstobart plus cisplatin with CCRT exhibits a trend toward better efficacy in unresectable LA-ESCC compared with SOC. The regimen achieved meaningful clinical responses with a tolerable safety profile, strongly supporting its further development.