Key Inclusion Criteria:

• Histologically confirmed, locally advanced/unresectable or metastatic, well-differentiated Grade 1, 2, or 3 NETs of pancreatic origin or extra-pancreatic origin.
• Allowed prior lines of therapy, based on the site of NET and functional status.
• Documented radiographic disease progression per RECIST 1.1, as assessed by the Investigator based on imaging assessments (computed tomography [CT] or magnetic resonance imaging [MRI]) within 12 months before randomization.
• Measurable disease according to RECIST 1.1 as determined by the Investigator.
• Archival tumor tissue is required, if available. If archival tumor tissue is not available, a fresh biopsy may be submitted if it can be safely and feasibly obtained. Every attempt should be made to provide tumor tissue.

Key Exclusion Criteria:

• Histologically confirmed neuroendocrine carcinomas (including small cell lung cancer), medullary thyroid cancer, pheochromocytoma, paraganglioma, Merkel cell carcinoma, and mixed neuroendocrine non-neuroendocrine neoplasm (MiNEN).
• Prior treatment with a vascular endothelial growth factor receptor (VEGFR) -targeting tyrosine kinase inhibitor or a mammalian target of rapamycin (mTOR) inhibitor.
• Systemic chemotherapy and any liver-directed or other ablative therapy within 4 weeks before randomization.
• Systemic radionuclide therapy within 6 weeks before randomization.
• Radiation therapy for bone metastases within 2 weeks, any other radiation therapy, except as indicated above, within 4 weeks before randomization.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.