Eligible patients had advanced/metastatic solid tumors refractory to standard therapy (Part 2 required NSCLC/ovarian/breast cancer with target expression), ECOG 0-1, and adequate organ function, excluding those with active CNS metastases, recent anticancer therapies, or uncontrolled infections.

Part 1 - PF-06664178 will be administered intravenously every 21 days in cohorts of 2 or more patients starting at a dose of 0.15 mg/kg. Increases in dose will continue until MTD is determined.Part 2 - patients with select tumor types (Non Small Cell Lung Cancer ovarian cancer, and breast cancer ) will be treated at the MTD selected in Part 1.

The study assesses first-cycle dose-limiting toxicities (DLTs) to determine MTD, along with treatment-emergent adverse events (TEAEs) and laboratory abnormalities (hematology, chemistry, coagulation, urinalysis) monitored at multiple timepoints during cycles 1-4 and follow-up.

Key outcomes include tumor response per RECIST 1.1, immunogenicity (anti-PF-06664178 antibodies), pharmacokinetics (Cmax, AUCtau, CL, Vss, halflife for PF-06664178, total antibody, and unconjugated payload), Trop-2 expression levels, and drug accumulation ratios across all study parts.

Advanced solid tumors resistant to standard therapy, or for which no other therapy was available, and at least one measurable lesion defined by Response Evaluation Criteria in Solid Tumors (RECIST version 1.1).

Once every 21 days as an intravenous infusion over approximately 60 min, doses starting from 0.15 mg/kg to 6.14 mg/kg.

In the 29 response-evaluable patients,the best overall response observed was limited to stable disease (SD) in 11 patients(37.90%) with PR or CR.

Doses explored ranged from 0.15 mg/kg to 4.80 mg/kg. Doses of 3.60 mg/kg,4.20 mg/kg and 4.80 mg/kg were considered intolerable due to DLTs. MTD and RP2D were not determined.