Inclusion Criteria:

- Adult patients, 18 years of age and older

- Adenocarcinoma of the stomach or gastroesophageal junction with inoperable,
metastatic disease, not amenable for curative therapy

- ECOG performance status 0 or 1

- Life expectancy >3 months

- Presence of tissue sample for immunohistochemistry assay of Met receptor and HER2
status (if unknown)

- Radiographic evidence of disease; measurable disease or non-measurable but evaluable
disease, according to the Response Evaluation Criteria in Solid Tumors (RECIST v1.1);
Patients with peritoneal disease would generally be regarded as having evaluable
disease and allowed to enter the trial.

- For women who are not postmenopausal or surgically sterile; agreement to use an
adequate method of contraception (e.g., hormonal implant) during the treatment period
and for at least 90 days after the last dose of onartuzumab/placebo and 6 months
after the last dose of oxaliplatin

- For men: agreement to use a barrier method of contraception during the treatment
period and for 90 days after the last dose of onartuzumab/placebo and 6 months after
the last dose of oxaliplatin

- Adequate laboratory values

Exclusion Criteria:

- HER2-positive tumor (primary tumor or metastasis)

- Previous chemotherapy for locally advanced or metastatic gastric carcinoma (adjuvant
or neoadjuvant chemotherapy must be completed at least 6 months prior to
randomization)

- Prior treatment with investigational drugs that target the HGF or Met pathway

- History of other malignancy within the previous 5 years, except for appropriately
treated and presumed cured carcinoma in situ of the cervix, non-melanoma skin
carcinoma, Stage 1 uterine cancer, and localized prostate cancer

- Receipt of an investigational drug within 28 days prior to study start

- Clinically significant gastrointestinal abnormalities, except from gastric cancer
(e.g., Crohn's disease)

- Significant history of cardiac disease

- Significant vascular disease

- Infection with human immunodeficiency virus, hepatitis B, or hepatitis C