FORAGER-1: A Study of Vepugratinib (LY3866288; LOXO-435) in Participants With Cancer With a Change in a Gene Called FGFR3

Inclusion Criteria:

* Cohort A1, C1, D1, and D2: Locally advanced or metastatic solid tumor malignancy with a qualifying FGFR3 alteration.
* Cohort A2, B2, B5 and B7: Urothelial cancer (UC) that is locally advanced or metastatic with a qualifying FGFR3 genetic alteration.
* Cohorts B1 and B4: Urothelial cancer that is locally advanced or metastatic and have received prior erdafitinib.
* Cohort B6: Muscle Invasive Bladder Cancer with a qualifying FGFR3 alteration.
* Cohort B7: Urothelial cancer that is locally advanced or metastatic with a qualifying FGFR3 genetic alteration and expression of human epidermal growth factor receptor 2 (HER2).
* Cohort B8: Low Grade Intermediate Risk Non-Muscle Invasive Bladder cancer and a qualifying FGFR3 genetic alteration.
* Measurability of disease:

  * Cohort A1, D1, and D2: Measurable or non-measurable disease as defined by Response Evaluation Criteria in Solid Tumors v 1.1 (RECIST v1.1).
  * Cohorts A2, B1, B2, B4, B5, B7, and C1: Measurable disease required as defined by RECIST v1.1.
  * Cohort B8: Baseline disease which includes at least 1 lesion.
* Have an Eastern Cooperative Oncology Group (ECOG) performance status of:

  * 0 or 1 for Cohorts A1, A2, B5, B6, B7, and B8.
  * Less than or equal to 2 for Cohorts B1, B2, B4, C1, DI and D2.
* Cohort B6: Must be eligible for radical cystectomy plus pelvic lymph node dissection and agree to undergo curative intent standard radical cystectomy plus pelvic lymph node dissection.

Exclusion Criteria:

* Participants with primary central nervous system (CNS) malignancy.
* Untreated or uncontrolled CNS metastases.
* Current evidence of corneal keratopathy or retinal disorder. Individuals with asymptomatic ophthalmic conditions may be eligible.
* Any serious unresolved toxicities from prior therapy.
* Significant cardiovascular disease.
* Prolongation of the QT interval corrected for heart rate using Fridericia's formula (QTcF).
* Active uncontrolled systemic infection or other clinically significant medical conditions.
* Participants who are pregnant, lactating, or plan to breastfeed during the study or within 6 months of the last dose of study treatment. Participants who have stopped breastfeeding may be enrolled.
* Cohort D1 only:

  * Have had renal transplantation.
  * Have a known history of nephrotic syndrome.
  * Have uncontrolled fluid overload, including clinically significant ascites, pleural effusion, or peripheral edema.
  * Have uncontrolled hypertension.
  * Are on hemodialysis or similar.
* Cohort D2 only:

  * Have a history of:
  * Ventricular tachycardia or ventricular fibrillation.
  * Hypertrophic obstructive cardiomyopathy unless managed concurrently with atrial fibrillation.
  * Wolff-Parkinson-White syndrome.
  * Second- or third-degree atrioventricular block unless a functioning pacemaker is in place.
  * Heart rate less than (\<) 50 bpm.
  * Have any of these medical conditions:
  * Severe respiratory insufficiency.
  * Sleep apnea syndrome.
  * Myasthenia gravis.
  * Acute narrow-angle glaucoma.
  * Active liver disease or clinically significant hepatic impairment.
  * History of myopathy or rhabdomyolysis with any HMG-CoA reductase inhibitor.