An Open-Label, International, Multicenter, Phase 1b/2a Study to Assess the Safety, Tolerability, and Efficacy of IDX-1197 in Combination with Xelox (Capecitabine and Oxaliplatin) or Irinotecan in Patients with Advanced Gastric Cancer

This is an open-label, Phase 1b/2a study to evaluate the safety and tolerability of
IDX-1197 and determine the MTD and RP2D in combination with XELOX or irinotecan in
patients with advanced gastric cancer.

Inclusion Criteria:

- Group 1, patients with treatment-naïve recurrent or advanced metastatic gastric
cancer including gastroesophageal junction or upper part of the stomach.

- Group 2, patients with recurrent or advanced metastatic gastric cancer including
gastroesophageal junction or upper part of the stomach, who were treated ≥2 times
with palliative chemotherapy before screening.

- At least 1 evaluable lesion for the dose escalation part and at least 1 measurable
lesion according to RECIST v1.1 for the dose expansion part.

- Eastern Cooperative Oncology Group (ECOG) performance status ≤1.

- Group 2 Part C, patients should have UGT1A1 genotype tested during or prior to
screening.

Exclusion Criteria:

- Symptomatic central nervous system or uncontrolled brain metastasis

- Carcinomatous meningitis or its history.

- For Group 1, patients who are HER 2 positive.

- Any other concurrent uncontrolled illness including, but not limited to, active or
ongoing symptomatic infection requiring IV antibiotic treatment, uncontrolled
diabetes, hepatic, renal, or respiratory illness.

- Severe or unstable angina, myocardial infarction or ischemia, symptomatic congestive
heart failure, arterial or venous thromboembolism requiring coronary artery bypass
graft or stent within the past 6 months or clinically significant cardiac
dysrhythmia or New York Heart Association class II ~ IV heart disease within 6
months of randomization.

- Uncontrolled hypertension

- Immunocompromised patients, such as patients known to be serologically positive for
HIV.

- Patients with known active Hepatitis B or C infection.

- Patients with known active or symptomatic pneumonitis, or history of non-infectious
pneumonitis requiring steroids.

- Diagnosis of a myelodysplastic syndrome/acute myeloid leukemia or its suspicious
characteristics.

- Any unresolved clinically significant Common Terminology Criteria for Adverse Events
(CTCAE) Grade ≥2 toxicity

- Resting ECG with measurable QTcF > 470 msec on 2 or more time points within a
24-hour period or family history of long QT syndrome.

- Current use of a cytochrome P3A4 inhibitor or inducer and strong uridine diphosphate
(UDP)-glucuronosyltransferase 1A1 (UGT1A1) inhibitors.