AZD0901 in Participants With Advanced Solid Tumours Expressing Claudin18.2

The list below is a summarised eligibility criteria for the study - refer to the study protocol for full criteria.

Master Inclusion Criteria applicable to all sub studies:

• Participant must be ≥ 18 years or the legal age of consent at the time of signingthe ICF.

• Participants who are CLDN18.2 positive.

• Must have at least one measurable lesion according to RECIST v1.1.

• ECOG performance status of 0 to 1 with no deterioration over the previous 2 weeksprior first day of dosing.

• Predicted life expectancy of ≥ 12 weeks.

• Adequate organ and bone marrow function as defined by protocol.

• Body weight > 35 kg.

• Participants are willing to comply with contraception requirements.

Sub study 1 Specific Inclusion criteria:

• Histologically confirmed adenocarcinoma of the stomach or gastroesophageal junction.

• Advanced or metastatic GC/GEJC.

• Maximum 2 prior lines of systemic treatment for unresectable or metastatic disease.

Sub study 2 Specific Inclusion criteria:

• Participants diagnosed with histologically confirmed metastatic or advanced PDAC.

• Availability of an archival sample or a fresh tumour biopsy taken at screening.

• No prior treatments for unresectable or metastatic disease. Priorneoadjuvant/adjuvant chemotherapy is permitted as long as participants progressed ≥ 6 months (183 days) from the last dose.

Sub study 3 Specific Inclusion criteria

• Histologically confirmed, unresectable advanced, or metastatic adenocarcinoma ofbiliary tract, including cholangiocarcinoma (intrahepatic or extrahepatic) andgallbladder carcinoma (NOTE: Ampullary cancers are not eligible).

• Documented radiographic or clinical disease progression on or after at least oneprior regimen and maximum 2 prior lines of systemic treatment for unresectable ormetastatic disease.

Master Exclusion Criteria applicable to all sub studies:

• Unstable or active peptic ulcer disease or digestive tract bleeding including butnot limited to clinically significant bleeding in the setting of prior CLDN18.2directed therapy.

• Participants with clinically significant ascites that require drainage.

• A history of drug-induced non-infectious ILD/pneumonitis.

• Central nervous system metastases or CNS pathology.

• Peripheral neuropathy, sensory, or motor ≥ Grade 2 at screening.

• History of another primary malignancy.

• Prior exposure to any MMAE-based ADC.

• Prior exposure to any CLDN18.2 targeted agents except anti-CLDN18.2 monoclonalantibody.

Sub study 1 Specific Exclusion criteria:

• Participants with HER2-positive (3+ by IHC, or 2+ by IHC, and positive by ISH) orindeterminate GC/GEJC unless they have failed/not tolerated/or are not eligible forstandard anti-HER2 therapy, where available.

• Any factors that increase the risk of QTc prolongation or risk of arrhythmic events.

• The use of concomitant medications known to prolong the QT/QTc interval.

Sub study 2 Specific Exclusion criteria:

• Known DPD enzyme deficiency based on local testing where testing is SoC.

• Use of strong inhibitor or inducer of UGT1A1.

• Use of strong inhibitors or inducers of CYP3A4.

• Known homozygous for the UGT1A1*28 allele based on local testing where testing isSoC.

Sub study 3 Specific Exclusion criteria

• Clinically significant biliary obstruction that has not resolved before enrollment.