A Study of LY4337713 in Participants With FAP-Positive Solid Tumors

Inclusion Criteria: * Must have clinical or imaging evidence of fibroblast activation protein (FAP) expression per local assessment * Must have histologically or cytologically confirmed diagnosis of one of the following: * Adenocarcinoma of the pancreas * Hormone receptor (HR)-positive human epidermal growth factor 2 (HER2)-negative breast cancer * HER2-positive breast cancer * Triple negative breast cancer (TNBC) * Platinum-resistant or refractory ovarian cancer * Other solid tumors * Gastric cancer (adenocarcinoma) * Colorectal cancer (CRC) * Esophageal cancer (squamous cell carcinoma or adenocarcinoma) * Cholangiocarcinoma * Must have received prior treatments as indicated below: * Phase 1a * Adenocarcinoma of the pancreas: Participants must have progressed after at least 1, but no more than 2 prior regimens for locally advanced unresectable or metastatic disease. * HR-positive HER2-negative breast cancer: Participants must have received less than or equal to (≤)5 prior lines of treatment for advanced or metastatic disease, which must include a cyclin-dependent kinase 4/6 inhibitor. * HER2-positive breast cancer: Participants must have progressed on at least 2 lines of HER2-targeted therapy, which should include at least 1 antibody-drug conjugate (ADC) for metastatic disease (if locally available). * TNBC: Participants must have progressed on at least 2 lines of therapy for metastatic disease. * Platinum-resistant or refractory ovarian cancer: Participants must have progressed on or after at least 1 platinum-based therapy. * Other solid tumors (gastric cancer, CRC, esophageal and cholangiocarcinoma): Participants must have received greater than or equal to (≥)1 prior line of systemic therapy for advanced or metastatic disease; including prior line(s) in combination with immunotherapy or vascular endothelial growth factor inhibitor. * Phase 1b: * Participants must have advanced or metastatic solid tumors and have received ≥1 prior line of therapy. * Must have an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 to 1. * Measured creatinine clearance ≥60 milliliters per minute (mL/min) Exclusion Criteria: * Have known active central nervous system (CNS) metastases or carcinomatous meningitis. * Have history of Grade 4 myelosuppression lasting greater than (\>)7 days, or Grade 3 myelosuppression requiring more than 6 weeks recovery. * Have significant cardiovascular disease * Have prolongation of the corrected QTcF \>470 milliseconds (msec) during screening. QTcF is calculated using Fridericia's Formula: QTcF = QT/(RR0.33) * Have evidence of ongoing and untreated urinary tract obstruction * Had previous hemi- or total-body radiation. * Had previous adoptive T-cell therapy (e.g., chimeric antigen receptor T-cell \[CAR-T therapy, T-cell receptor \[TCR\] therapy, etc.) * Unable to lie flat during, or otherwise tolerate, single photon emission computed tomography (SPECT), positron emission tomography (PET), computed tomography (CT) or magnetic resonance imaging (MRI).