This study is being performed to evaluate the efficacy and safety of capecitabine in combination with tesetaxel versus capecitabine in combination with placebo as second-line treatment for patients with gastric cancer.

Key inclusion criteria:

1. Histologically or cytologically confirmed gastric adenocarcinoma, including gastric or gastroesophageal-junction adenocarcinoma (Histologically confirmed adenocarcinoma of the lower esophagus acceptable with radiographic or endoscopic documentation of gastroesophageal-junction or proximal-stomach involvement.)
2. Measurable disease (revised RECIST) based on computed tomography, or nonmeasurable disease
3. ECOG performance status 0 or 1
4. Treatment with only 1 prior regimen (as first-line therapy) that must have included a fluoropyrimidine and a platinum-containing agent (Prior adjuvant or neo-adjuvant chemotherapy acceptable provided 6 months elapsed between the end of this therapy and the start of first-line therapy.)
5. Disease progression after the start of the 1 prior regimen based on computed tomography
6. Adequate bone marrow, hepatic, and renal function
7. Ability to swallow an oral solid-dosage form of medication

Key exclusion criteria:

1. Squamous cell gastric carcinoma
2. Bone-only metastatic disease
3. History or presence of brain metastasis or leptomeningeal disease
4. Operable gastric or gastroesophageal-junction cancer
5. HER2-positive disease if the patient has not previously been treated with an anti-HER2 agent
6. Uncontrolled diarrhea, nausea, or vomiting
7. Known malabsorptive disorder
8. Significant medical disease other than gastric cancer
9. Presence of neuropathy > Grade 1 (NCI Common Toxicity Criteria)
10. Prior treatment (including adjuvant therapy) with a taxane or other tubulin-targeted agent (indibulin, eribulin, etc.)
11. Prior radiation therapy to more than 25% of the bone marrow
12. Need to continue any regularly-taken medication that is a potent inhibitor or inducer of the CYP3A pathway
13. Pregnancy or lactation