Study of BGB-290 or Placebo in Patients With Advanced or Inoperable Gastric Cancer

This is a double-blind, placebo controlled, randomized multicenter global phase 3 study
comparing the efficacy and safety of single agent poly (ADP-ribose) polymerase (PARP)
inhibitor BGB-290 to placebo as maintenance therapy in subjects with advanced gastric cancer
who have responded to first line platinum based chemotherapy. Subjects are randomized 1:1 to
BGB-290 (Arm A) or placebo (Arm B). Randomization will be stratified by geography, biomarker
status, and ECOG performance status.

Patients will undergo tumor assessments at screening and then every 8 weeks, or as clinically
indicated. Administration of BGB-290 or placebo will continue until disease progression,
unacceptable toxicity, death, or another discontinuation criterion is met.

After end of treatment, long-term follow-up assessments include tumor imaging every 8 weeks
for those patients without disease progression, survival status, and new anticancer therapy.

Inclusion Criteria:

1. Age ≥ 18 years.

2. Signed informed consent.

3. Histologically confirmed inoperable locally advanced or metastatic adenocarcinoma of
the stomach or gastroesophageal junction.

4. Received platinum based first line chemotherapy for ≤ 28 weeks.

5. Confirmed partial response (PR) maintained for ≥ 4 weeks or complete response (CR).

6. Able to be randomized to study ≤ 8 weeks after last platinum dose.

7. ECOG performance status ≤ 1.

8. Adequate hematologic, renal and hepatic function.

9. Must be able to provide archival tumor tissue for central biomarker assessment.

10. Females of childbearing potential and non-sterile males must agree to use highly
effective methods of birth control throughout the course of study and at least up to 6
months after last dosing.

Exclusion Criteria:

1. Unresolved acute effects of prior therapy ≥ Grade 2.

2. Prior treatment with PARP inhibitor.

3. Chemotherapy, biologic therapy, immunotherapy or other anticancer therapy ≤ 14 days
prior to randomization.

4. Major surgery or significant injury ≤ 2 weeks prior to start of study treatment.

5. Diagnosis of myelodysplastic syndrome (MDS) or active bleeding disorder.

6. Other diagnoses of significant malignancy

7. Leptomeningeal disease or brain metastasis

8. Inability to swallow capsules or disease affecting gastrointestinal function.

9. Active infections requiring systemic treatment.

10. Clinically significant cardiovascular disease

11. Pregnant or nursing females.