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Proffered paper session on Thoracic cancers

LBA4 - GEMSTONE-302: A phase III study of platinum-based chemotherapy (chemo) with placebo or CS1001, an anti-PDL1 antibody, for first-line (1L) advanced non-small cell lung cancer (NSCLC)


21 Nov 2020


Proffered paper session on Thoracic cancers


Cytotoxic Therapy

Tumour Site

Non-Small Cell Lung Cancer


Caicun Zhou


Annals of Oncology (2020) 31 (suppl_6): S1386-S1406. 10.1016/annonc/annonc367


C. Zhou1, Z. Wang2, Y. Sun3, L. Cao4, Z. Ma5, R. Wu6, Y. Yu7, W. Yao8, J. Chang9, J. Chen10, W. Zhuang11, J. Cui12, X. Chen13, Y. Lu14, H. Shen15, P. Li16, J. Wang16, B. Sun16, D. Lu16, J. Yang16

Author affiliations

  • 1 Oncology, Shanghai Pulmonary Hospital, Tongji University, 200433 - Shanghai/CN
  • 2 The Department Of Respiratory Oncology, Beijing Cancer Hospital, 100142 - Beijing/CN
  • 3 Oncology Department, Jinan Central Hospital, jinan/CN
  • 4 Respiratory Medicine Department, Anhui Provincial Hospital, Hefei/CN
  • 5 Respiratory Medicine, The Affiliated Cancer Hospital of Zhengzhou University, Henan Cancer Hospital, Zhengzhou/CN
  • 6 Oncology Department, Shengjing Hospital of China Medical University, Hua Xiang Branch Hospital, Shenyang/CN
  • 7 Department Of Respiratory Medicine, Harbin Medical University Cancer Hospital, Harbin/CN
  • 8 Department Of Thoracic Oncology, Sichuan Cancer Hospital & Institute, Chengdu/CN
  • 9 Oncology, Fudan University Shanghai Cancer Center, 200032 - Shanghai/CN
  • 10 Thoracic Oncology, Hunan Cancer Hospital, Changsha/CN
  • 11 Thoracic Oncology, Fujian Provincial Cancer Hospital, 350014 - Fuzhou/CN
  • 12 Pharmacology Base, The First Hospital of Jilin University, 130021 - Changchun/CN
  • 13 Department Of Oncology, Affiliated Hangzhou First People's Hospital, Zhejiang University School of Medicine, Hangzhou/CN
  • 14 Thoracic Oncology, West China Hospital, Sichuan University, Chengdu/CN
  • 15 Department Of Oncology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Zhejiang/CN
  • 16 Clinical Development And Regulatory Affairs, CStone Pharmaceuticals (Su Zhou) Co., Ltd, Suzhou/CN


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Abstract LBA4


CS1001, a full-length, fully human PD-L1 targeted IgG4 (s228p) mAb, was well tolerated and had demonstrated promising anti-tumor activities across a range of cancers including NSCLC in phase Ia/Ib study. GEMSTONE-302 is a randomized, double-blind, phase III study to compare the efficacy and safety of chemo with or without CS1001 as 1L treatment for advanced NSCLC.


Eligible pts with untreated advanced NSCLC were stratified by histology (sq vs nsq), PD-L1 expression (≥1% vs <1%), and ECOG PS (0 vs 1) and randomized 2:1 to receive CS1001 (1200 mg, Q3W, IV)/placebo + chemo up to 4 cycles, followed by CS1001 or placebo maintenance up to 2 yrs. In nsq pts, pemetrexed was also given as maintenance therapy. The primary endpoint is investigator-assessed PFS (RECISIT v1.1).


A total of 479 pts (320 in CS1001+chemo, 159 in placebo+chemo) were enrolled in the study. Baseline characteristics were balanced between 2 arms. As of 8 Jun 2020, at the pre-planned PFS interim analysis (median follow-up 8.67 vs 8.34 mo), the mPFS was significantly prolonged in the CS1001+chemo arm (stratified HR 0.50 [0.39-0.64], p<.0001; mPFS 7.8 vs 4.9 mo). ORR was 61.4% and 39.2% in CS1001+chemo and placebo+chemo arms, respectively. OS data was immature, but a clinical benefit trend was observed, (stratified HR 0.66 [0.44-0.97]; mOS NR vs 14.75 mo). Subgroup analyses demonstrated clinical benefits across histology and PD-L1 expression levels. Grade ≥3 TEAEs were reported in 61.9% and 61.6% of pts in CS1001+chemo and placebo+chemo arms, respectively. The 2 arms had similar safety profile, with the exception of mostly Grade 1 and 2 immune-related AEs in CS1001+chemo arm. No new unexpected safety signals were found.


This is the first phase III trial conducted in China on an anti-PD-L1 mAb plus chemo that enrolls advanced, treatment-naive sq and nsq NSCLC pts. CS1001 combined with chemo shows statistically significant and clinically meaningful benefit in PFS with a well-tolerated safety profile against chemo across histology and PD-L1 expression levels. It will potentially become a new SOC for 1L treatment of advanced NSCLC once receiving regulatory approval.

Clinical trial identification


Editorial acknowledgement

Legal entity responsible for the study

CStone Pharmceuticals.


CStone Pharmaceuticals.


P. Li, J. Wang, B. Sun: Shareholder/Stockholder/Stock options, Full/Part-time employment: CStone Pharma. D. Lu: Full/Part-time employment: CStone Pharma. J. Yang: Leadership role, Shareholder/Stockholder/Stock options, Full/Part-time employment: CStone Pharma.

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