The purpose of this study is to evaluate the clinical efficacy and safety of HLX22 in the HER2+ Locally Adanved or Metastatic Gastric Cancer as the first-line therapy.This study consists of three periods, screening period (28 days), treatment period and follow-up period (including safety follow-up, survival follow-up).Subjects can be enrolled into this study only if they meet inclusion criteria and do not meet exclusion criteria. The enrolled subjects will receive an intravenous infusion of HLX22/placebo and SOC(standard of care: Trastuzumab + XELOX) once every 3 weeks until the loss of clinical benefit, death, intolerable toxicity, withdrawal of informed consent or other reasons as specified in the protocol(whichever occurs earlier).
HLX22(25mg/kg) or HLX22(15mg/kg) or placebo will be administered intravenously \[IV\] on day 1 of each 3-week cycle. Trastuzumab (8 mg/kg loading dose, 6 mg/kg maintenance dose) will be administered IV on day 1 of each 3-week cycle. SOC chemotherapy is XELOX (1000 mg/m\^2 capecitabine administered orally twice daily \[BID\] on days 1-14 of each 3-week cycle and 130 mg/m\^2 oxaliplatin administered IV on Day 1 of each 3-week cycle).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
150
IV Q3W D1
IV Q3W D1
IV Q3W D1
IV Q3W D1
PO Q3W D1-D14
Shanghai East Hospital
Shanghai, China
Progression Free Survival (PFS) per RECIST 1.1 assessed by IRRC(Independent Radiology Review Committee)
PFS is defined as the time from randomization to the first documented disease progression per RECIST 1.1 as assessed by IRRC or death due to any cause, whichever occurs first. PFS will be determined for each treatment arm
Time frame: Up to 5 years
Objective Response Rate (ORR) per RECIST 1.1 assessed by IRRC
ORR is defined as the percentage of participants who have a Complete Response (\[CR\], disappearance of all evidence of disease) or Partial Response (\[PR\], regression of measurable disease and no new sites) per RECIST 1.1 as assessed by IRRC. ORR will be determined for each treatment arm.
Time frame: Up to 5 years
Overall Survival (OS)
OS is defined as the time from randomization to death due to any cause. OS will be determined for each treatment arm.
Time frame: Up to 5 years
Duration of Response (DOR) per RECIST 1.1 assessed by IRRC
For participants who demonstrate CR or PR, DOR is defined as the time from first response (CR or PR) to subsequent disease progression or death from any cause, whichever occurs first. DOR will be determined for each treatment arm
Time frame: Up to 5 years
Adverse Events (AE)
An AE is any untoward medical occurrence in a participant that is temporally associated with the use of study treatment, whether or not considered related to the study treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study treatment. The number of participants who experience an AE will be reported for each treatment arm.
Time frame: Up to 5 years
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