A Study of TAK-164 in Participants With Advanced Gastrointestinal (GI) Cancer Expressing Guanylyl Cyclase C (GCC)

The drug being tested in this study is a novel antibody-drug conjugate (ADC) called TAK-164.
TAK-164 is being evaluated in participants with advanced GCC-positive GI cancer (Part A) or
CRC (Part B) to determine safety, tolerability, and pharmacokinetics (PK) and MTD/RP2D of
TAK-164, as well as the preliminary efficacy. The study will include approximately 95
evaluable participants.

In Part A (Escalation), approximately 45 participants with GI carcinoma will be enrolled in 2
arms planned dose escalation scheme. Those include patients with various GI malignancies such
as carcinomas of esophagus, stomach, colon, and pancreas. The starting dose for Arm 1 will be
0.004 mg/kg of TAK-164 administered IV on Day 1 every 3 Week (Q3W). Arm 2, will enroll
approximately 20 participants after at least 4 dose levels of TAK-164 in Part A. TAK-164 will
be administered IV on Days 1 and 15 every 2 Week (Q2W).

In Part B (Expansion), approximately 50 participants will be enrolled to receive TAK-164
infusion at determined RP2D in Part A. Participants will follow either the Q2W schedule or
the Q3W schedule and will be followed until disease progression (PD), unacceptable toxicity,
or until they choose to withdraw consent.

This multi-center trial will be conducted to include United States and EU. The overall time
to participate in this study is up to 55 months. Participants will attend an end of study
(EOS) visit 30 days after the last dose of TAK-164 or just prior to the start of subsequent
antineoplastic therapy, whichever occurs first.

Inclusion Criteria:

1. Histologically or cytologically confirmed measurable advanced and/or metastatic solid
GI tumor that expresses GCC protein (H-score greater than [>] 10), for which standard
treatment is no longer effective or does not offer curative or life-prolonging
benefit. For the escalation part of the study (Part A), GI malignancies include, but
are not limited to, metastatic colorectal carcinoma (mCRC), gastric carcinoma,
esophageal carcinoma, small intestine cancer, and pancreatic cancer. The expansion
part of the study (Part B) is limited to participants with CRC.

2. Male or female participants 18 years or older.

3. Adequate bone marrow function, defined as an absolute neutrophil count (ANC) of
greater than or equal to (>=) 1.5*109 per liter (/L), platelet count >=100*109/L, and
hemoglobin >=9 gram per deciliter (g/dL). Receiving transfusions or hematopoietic
growth factors to meet enrollment criteria is not allowed within 14 days preceding the
first dose of study drug.

4. Eastern Cooperative Oncology Group (ECOG) performance score of 0 or 1.

5. Life expectancy of at least 12 weeks.

6. Completion of prior chemotherapy, biologic therapy, immunotherapy, or radiation
therapy at least 4 weeks prior to enrollment.

7. Resolution of all toxic effects of prior treatments (except alopecia) to Grade <=1 NCI
CTCAE, Version 5.

8. A portion of participants should have tumors amenable for serial biopsy and a
willingness to provide consent for pharmacodynamic assessment.

Exclusion Criteria:

1. Treatment with anticancer chemotherapy or biologic therapy or with an experimental
anticancer agent within 28 days of the initial dose of study drug.

2. Diagnosed or treated for another malignancy within 2 years before administration of
the first dose of study drug, or previously diagnosed with another malignancy and have
any evidence of residual disease. Participants with nonmelanoma skin cancer or
carcinoma in situ of any type are not excluded if they have undergone complete
resection.

3. Participant has a history of severe allergic or anaphylactic reactions to recombinant
proteins or excipients used in TAK-164 formulation.

4. Use of strong cytochrome P3A (CYP3A) inhibitors and CYP3A inducers or inhibitors or
modulators of P-glycoprotein (P-gp) or breast cancer resistance protein (BCRP) within
1 week before the first dose of study drug.

5. For participants enrolled in studies in which tumor biopsies are obtained:

- Known bleeding diathesis or history of abnormal bleeding, or any other known
coagulation abnormalities that would contraindicate the tumor biopsy procedure.

- Ongoing therapy with any anticoagulant or antiplatelet agents (example, aspirin,
clopidogrel, heparin, or warfarin).