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 (including ovarian carcinosarcoma)
  * 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 received 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 received 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 received at least 2 lines of therapy for metastatic disease.
    * Platinum-resistant or refractory ovarian cancer: Participants must have received 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 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).