Overview

This clinical trial is studying advanced solid tumors. Solid tumors are cancers that start in a part of your body like your lungs or liver instead of your blood. Once tumors have grown bigger in one place but haven't spread, they're called locally advanced. If your cancer has spread to other parts of your body, it's called metastatic. When a cancer has gotten so big it can't easily be removed or has spread to other parts of the body, it is called unresectable. These types of cancer are harder to treat.

Patients in this study must have cancer that has come back or did not get better with treatment. Patients must have a solid tumor cancer that can't be treated with standard of care drugs.

This clinical trial uses an experimental drug called PF-08052666/SGN-MesoC2. PF-08052666/SGN-MesoC2 is a type of antibody-drug conjugate (ADC). ADCs are designed to stick to cancer cells and kill them. They may also stick to some normal cells.

This study will have 3 parts. Part A and Part B of the study will find out how much PF-08052666/SGN-MesoC2 should be given to participants. Part C will use the information from Parts A and B to see if PF-08052666/SGN-MesoC2 is safe and if it works to treat solid tumor cancers.

Eligibility

Inclusion Criteria:

• An Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1.
• Participants must have histologically- or cytologically-confirmed metastatic or locally advanced unresectable ovarian cancer, non-small cell lung cancer (NSCLC), pancreatic adenocarcinoma, endometrial cancer (EC), colorectal cancer (CRC), mesothelioma.
• Must have at least one measurable lesion at baseline based on RECIST v1.1.
• Archival tumor tissue is required, or, if unavailable, a fresh tumor biopsy (if it is safe and feasible) during the screening period.
• Participants weighing ≥40 kg
• Additional inclusion criterion for platinum resistant ovarian cancer (PROC) participants: Histologically or cytologically documented invasive epithelial ovarian, primary peritoneal, or fallopian tube cancer (tumors with pseudomyxomatous or mucinous histology are excluded) or advanced predominantly epithelioid peritoneal, must have relapsed or progressed following local standard therapies or for which no standard therapy is available.
• Platinum prior exposure unless it is contraindicated or not available.
• Participants with known FRa high expression, must have progressed after mirvetuximab soravtansine or other FRa-directed therapy) unless contraindicated or not available. Participants whose cancer is associated with homologous recombination deficiency (HRD)-positive status must have been exposed to PARP inhibitors, unless contraindicated or not available.
• Additional inclusion criterion for pancreatic ductal adenocarcinoma (PDAC) participants (Part A only): Histologically or cytologically documented, locally advanced unresectable or metastatic pancreatic adenocarcinoma, including recurrence of previously resected disease.
• Participant must have progressed after standard cytotoxic therapies, or for which no standard therapy is available. Participants must have received fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy, gemcitabine and nab-paclitaxel combination or gemcitabine-based chemotherapy.
• Additional inclusion criterion for NSCLC participants (Part A only): Histologically or cytologically confirmed advanced and/or metastatic NSCLC, must have progressed after standard therapies, or for which no standard therapy is available.
• Participants do not need to have expression of MSLN in tumor to be selected for Part C enrollment unless retrospective analysis of the immunohistochemistry (IHC) data in dose escalation suggests it as a requirement.
• a. If participants have a specific mutation for which standard therapy is available (eg, ALK, ROS1, MET, NTRK, BRAF V600E, EGFR Exon 20 ins, RET, KRAS G12C, HER2), they must have documented progression after treatment with appropriate tyrosine kinase inhibitor or other agent and have documented progression after platinum doublet chemotherapy treatment, unless not tolerated, contraindicated, or not available.
• b. If participants do not have a specific mutation for which standard therapy is available, they must have documented progression after treatment with a check point inhibitor and platinum based chemotherapy, unless not tolerated, contraindicated, or not available.
• Additional inclusion criterion for CRC participants (Part A only): Histologically confirmed metastatic or locally advanced colorectal adenocarcinoma.
• Participant must have progressed after standard therapy, or for which no standard therapy is available. Participants must have received fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy, unless not tolerated, contraindicated, or not available.
• Participants with microsatellite instability (MSI)-H/mismatch repair deficient (dMMR) tumors must have received treatment with a PD-1 mAb, unless not tolerated or available. If participants have an BRAF mutation or other mutations, they must have documented progression after treated with appropriate therapies (eg, encorafenib + cetuximab), unless not tolerated or available. Particpants with HER2 positive tumors, must have received treatment with HER2-directed therapies (eg, tucatinib + trastuzumab), unless not tolerated or available.
• Participants do not need to have expression of MSLN in tumor to be selected for Part C enrollment unless retrospective analysis of the IHC data in dose escalation suggests it as a requirement.
• Additional inclusion criteria for EC participants (Part A only): Participant must have received at least 1 line of platinum-based chemotherapy.
• Participant must have received up to 2 lines of systemic therapy in metastatic setting.
• If appropriate by biomarker status (including but not limited to microsatellite instability [MSI] and dMMR status) and available per local SOC, must have received a prior PD-1 inhibitor and/or the combination of pembrolizumab and lenvatinib, unless not tolerated.
• Additional inclusion criteria for mesothelioma participants (Part A only): Histologically or cytologically confirmed advanced and/or metastatic mesothelioma, must have progressed after standard therapies, or for which no standard therapy is available.
• Additional inclusion criteria for all tumor types (Parts B and C only): Participants must have histologically- or cytologically-confirmed metastatic or locally advanced unresectable ovarian cancer, non-small cell lung cancer (NSCLC), pancreatic adenocarcinoma, endometrial cancer (EC), colorectal cancer (CRC), or mesothelioma.
• Participants must not have received more than 2 lines of cytotoxic systemic therapy in metastatic setting.

Exclusion Criteria:

• Participants previously received or is currently receiving the following anticancer medications or investigational drugs will be excluded:
  • Any systemic anticancer therapy or focal radiotherapy within 4 weeks prior to first dose of PF-08052666or within 2 weeks prior to the first dose of PF-08052666if the underlying disease has progressed on treatment.
  • For Part C, prior anti-Mesothelin (MSLN) antibody (mAb or BsAb), MSLN- directed ADC.
• Major surgery (excluding placement of vascular access) within 4 weeks, or minor

  surgery within 7 days, prior to first dose of study intervention.

Participants must have recovered adequately from the toxicity or complications from the surgery prior to starting PF-08052666. Participants who have planned major surgery during the treatment period must be excluded from the study.

• History of another malignancy within 3 years before the first dose of study intervention, or any evidence of residual disease from a previously diagnosed malignancy. Exceptions are malignancies with a negligible risk of metastasis or death.
• Known to be positive for human immunodeficiency virus (HIV). Participants with severe or uncontrolled systemic diseases, including uncontrolled hypertension, uncontrolled diabetes mellitus, or active bleeding diatheses.
• Participants with medical history of clinically significant lung diseases (eg, interstitial pneumonia, pneumonitis, pulmonary fibrosis, and severe radiation pneumonitis) or who are suspected to have these diseases by imaging at screening period.
• Previously untreated brain metastases. Participants who have received radiation or surgery for brain metastases are eligible if therapy was completed at least 4 weeks prior to initiation of study treatment, there is no evidence of central nervous system (CNS) disease progression, and there is no requirement for chronic corticosteroid therapy. Leptomeningeal metastases or spinal cord compression due to disease.