M1231 in Participants With Solid Tumors

Inclusion Criteria:

For Part 1 and 2:

The Investigator reviews the medical history, menstrual history, and recent sexual activity to decrease the risk for inclusion of a female with an early undetected pregnancy

For Part 1:

Locally advanced or metastatic disease that is intolerant or refractory to standard therapy or for which no standard therapy is judged appropriate by the investigator
Participants with solid tumors expressing or likely to expressing EGFR and MUC1, including but not limited to lung cancer, squamous esophageal cancer, head and neck squamous cell carcinoma, breast cancer and ovarian cancer, should be prioritized for enrollment

For Part 2:

Cohort A: Participants must have progressed on at least 2 prior lines of therapy
Cohort B: Participants must have progressed on at least 1 prior line of platinum therapy and for microsatellite instability-high (MSI-H) at least 1 prior line with pembrolizumab
Eastern Cooperative Oncology Group (ECOG) Performance Status less than 1
Tumor accessible for biopsies and agreement to conduct fresh tumor biopsies at Screening and before first dosing

Exclusion Criteria:

Participants not recovered from adverse events (AE) (less than or equal to Grade 1) related to previous therapies (excluding Grade 1 neuropathy and alopecia)
Participant has a history of a second malignancy within 3 years before the date of enrollment
Known brain metastasis
Unstable angina, myocardial infarction, congestive heart failure or a coronary revascularization procedure within 180 days of study entry
Cerebrovascular accident/stroke
Diagnosis of fever within 1 week prior to study intervention administration
Life expectancy of less than 4 months
Steroid therapy for anti-neoplastic intent taken less than 7 days prior to the first dose of study intervention
Major surgery within 4 weeks prior to start of study intervention
Received growth factors (including erythropoietin (EPO), darbepoetin, granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), and platelet stimulators or transfusions within 2 weeks prior to the first day of study intervention