A Study to Investigate ALE.P03 as Monotherapy in Adult Patients With Selected Advanced or Metastatic CLDN1+ Solid Tumors

Inclusion Criteria:

* Have histologically and cytologically metastatic confirmed advanced or metastatic colorectal cancer, intrahepatic cholangiocarcinoma, squamous non-small cell lung cancer, urothelial carcinoma, and cervical squamous cell carcinoma.
* Have documented radiological disease progression at study entry.
* Have provided tissue for CLDN1 (Claudin-1) analysis in a central laboratory.

Phase I Dose Escalation:

\- Received and being refractory/intolerant to available systemic standard of care (SOC) regimens (based on local institutional guidelines) for advanced disease.

Phase I RDE and Phase II:

* Received 1-2 available systemic SOC regimens (based on local institutional guidelines) for advanced disease and being refractory or intolerant to treatment.
* Patients with actionable oncogenic drivers: received feasible targeted therapy.

Applicable for Phase I Dose Escalation, Phase I RDE and Phase II:

* Measurable disease per RECIST 1.1, as determined by the site.
* Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Groups Performance Status.
* Demonstrate adequate bone marrow and organ function as per the protocol.

Exclusion Criteria:

* SqNSCLC and CSCC: diagnosed with a tumor of predominantly non-squamous histology result or adenocarcinoma.
* Has received antineoplastic therapies prior to study intervention within specified time frame.
* Has rapidly progressing disease.
* Has known active central nervous system metastases and/or carcinomatous meningitis.
* Has a history of (non-infectious) interstitial lung disease/pneumonitis that required steroids or current symptomatic or clinically significant pneumonitis requiring steroids and/or immunosuppressive therapies.
* Has clinically significant gastrointestinal bleeding.
* Has an active infection requiring systemic treatment.
* Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the clinical study.