The trial was terminated for strategic reasons. The decision was not based on any safety and/or efficacy concerns.

This study will test the safety of a drug called PF-08046031 in participants with melanoma and other solid tumors that have no current approved treatment or have spread through the body. It will also study the side effects of this drug. A side effect is anything a drug does to the body besides treating the disease. The study will have 3 parts. Part A and B of the study will find out how much PF-08046031 should be given to participants. Part C will use the information from Parts A and B to see if PF-08046031 is safe and if it works to treat solid tumor cancers.

Inclusion Criteria:

• Participants in Part 1 (dose escalation) must have histologically- or cytologically-confirmed metastatic or unresectable cutaneous melanoma. They must have progressive disease following at least 1 prior anti programmed death-1 (PD 1)/programmed death-ligand 1 (PD L1) immunotherapy containing regimen (either as monotherapy, or in combination with other checkpoint inhibitors or other therapies) and should have no appropriate standard therapy available at the time of enrollment in the judgment of the investigator.
• Participants in Part 2 (dose optimization) must have histologically- or cytologically-confirmed metastatic or unresectable cutaneous melanoma. They must have progressive disease following at least 1 prior anti PD 1/PD L1 immunotherapy containing regimen (either as monotherapy, or in combination with other checkpoint inhibitors or other therapies) but not more than 2 total prior lines of systemic therapy and should have no appropriate standard therapy available at the time of enrollment in the judgment of the investigator.
• For Part 3 (dose expansion): Participants must have histologically- or cytologically confirmed metastatic or unresectable solid malignancy from 1 of the following tumor types: cutaneous melanoma, NSCLC, HNSCC, esophageal cancer.

Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1 Measurable disease per RECIST v1.1 at baseline

• Participants who have refused available standard of care therapies are not eligible.

Exclusion Criteria:

• Active cerebral/meningeal disease related to the underlying malignancy. Previous exposure to CD228-targeted therapy, vedotin or an MMAE-containing agent, or any taxane containing regimen for advanced disease.

Melanoma subtypes including uveal, and mucosal are excluded. Chemotherapy, definitive radiotherapy, biologics, and/or other antitumor treatment with immunotherapy that is not completed 4 weeks prior to first dose of study intervention, or within 2 weeks prior to first dose of study intervention if the underlying disease has progressed on treatment

• Grade 3 or higher pulmonary disease unrelated to underlying malignancy. Previous history of non-infectious interstitial lung disease (ILD) or pneumonitis that required steroids, current ILD or pneumonitis, or suspected ILD or pneumonitis that cannot be ruled out by imaging at screening.

Other protocol specific criteria might apply.

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

None (Open Label)