A Study of Pimitespib in Combination with Imatinib in Patients with GIST (CHAPTER-GIST-101)

Inclusion Criteria:

• Provided written informed consent

• Histologically confirmed GIST

• Has radiographic progression based on RECIST 1.1 during or within 6 months of thelast imatinib administration at enrollment. If surgery/radiotherapy has beenperformed, radiographic progression based on RECIST 1.1 with imatinib must have beenobserved after the last surgery /radiotherapy

• Has at least one measurable lesion based on the RECIST version 1.1, except lymphnodes (not dependent on size), which should be chosen as nontarget lesions;

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1

Exclusion Criteria:

• Corrected visual acuity < 0.5 (using the International Visual Acuity MeasurementStandard) for both eyes

• Received treatment with any other line of therapy besides imatinib for advanced GIST

• History of total gastrectomy and/or whole resection of the small intestine

• A serious illness or medical condition

• Previous or concurrent cancer that is distinct in primary disease or histology fromcancer that is being evaluated in this study. However, any previous cancercuratively treated > 5 years before the enrollment can be eligible

• Pregnancy or lactation (including lactation interruption)