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

The purpose of the study is to test the safety of the medicine called Felmetatug Vedotin alone and with pembrolizumab in participants with solid tumors. It will also look at the side effects of this medicine. A side effect is anything a medicine does to the body besides treating the disease.

This study is seeking for participants who either have cancer:

• that has spread in the body near where it started (locally advanced) and cannot be removed (unresectable),
• has spread through the body (metastatic), or have some cancer left over after surgery.

This study will have five parts.

• Parts A and B of the study will find out how much Felmetatug Vedotin should be given to participants.
• Part C will use the amount found in Parts A and B to find out how safe Felmetatug Vedotin is and if it works to treat solid tumor cancers.
• Part D will find out if and how much Felmetatug Vedotin can be given with pembrolizumab.
• Part E will use the amount found in Part D to find out how safe Felmetatug Vedotin with pembrolizumab is and if it works to treat triple negative breast cancer.

Inclusion Criteria:

For Parts A, B, and C:

• Participants must have one of the following histologically or cytologically confirmed locally advanced unresectable or metastatic solid tumor types:

  • High-grade serous epithelial ovarian cancer, primary peritoneal cancer, or fallopian tube cancer
  • HER2-negative, HR positive breast cancer
  • Triple-negative breast cancer (TNBC)
  • Endometrial carcinoma
  • Non-small cell lung cancer (Squamous cell carcinoma [SqCC], Adenocarcinoma [AC])
  • Cholangiocarcinoma or gallbladder carcinoma
  • Adenoid cystic carcinoma (ACC) For Part D: Participants must have histologically or cytologically confirmed locally advanced unresectable or metastatic TNBC.

For Part E:

• Cohort E1: Participants must have histologically or cytologically confirmed locally advanced unresectable or metastatic TNBC and must have CPS≥10 by local testing

• Cohort E2: Participants must have histologically or cytologically confirmed locally advanced unresectable or metastatic TNBC and must have CPS<10 by local testing

• Cohort E3: Participants must have triple negative breast cancer with residual disease following neoadjuvant therapy and definitive surgery

  • Parts A and B: Participants must have disease that is relapsed or refractory or be intolerant to SOC therapies, and, in the judgement of the investigator, should have no appropriate SOC therapeutic option
  • Part C: Participants must have disease that is relapsed or refractory or be intolerant to SOC therapies.
  • Part D and E1/E2: Participants must have had no prior treatment for locally advanced unresectable or metastatic TNBC
  • Part E3: Participants must have completed at least 6 cycles of neoadjuvant therapy for locally advanced unresectable or metastatic TNBC
  • Tumor tissue is required for enrollment.
  • Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
  • Measurable disease per RECIST version 1.1 at baseline (not applicable for E3 participants).

Exclusion Criteria:

• History of another malignancy within 3 years before the first dose of study drug. Any evidence of residual disease from a previously diagnosed malignancy. Exceptions are malignancies with a negligible risk of metastasis or death.

• Known active central nervous system metastases. Participants with previously treated brain metastases may participate provided they:

  • are clinically stable for at least 4 weeks prior to study entry after brain metastasis treatment
  • have no new or enlarging brain metastases
  • and are off corticosteroids prescribed for symptoms associated with brain metastases for at least 7 days prior to the first dose of study treatment.

• Carcinomatous meningitis

• Previous receipt of an MMAE-containing agent or an agent targeting B7-H4

• Pre-existing neuropathy ≥ Grade 2 per National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) Version 5.0

• Corneal disease or injury requiring treatment or active monitoring

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.