Inclusion Criteria: 

• Histologically or cytologically confirmed solid tumor malignancy that is advanced or metastatic or is surgically unresectable. 
• Radiographically measurable disease (per RECIST v1.1 or RANO for primary brain tumors). Tumor lesions located in a previously irradiated area or in an area subjected to other loco-regional therapy are considered measureable if progression has been clearly demonstrated in the lesion. 
• Documentation of an FGFR1-3 gene mutation or translocation. 
• Objective progression after at least 1 prior therapy and no therapy available that is likely to provide clinical benefit. Participants who are intolerant to or decline the approved therapy are eligible only if they have no therapy available that is likely to provide clinical benefit. 
• Eastern Cooperative Oncology Group performance status 0 to 2.
• Baseline archival tumor specimen (if < 12 months from date of screening) or willingness to undergo a pretreatment tumor biopsy to obtain the specimen. Must be a tumor block or approximately 15 unstained slides from biopsy or resection of primary tumor or metastasis. 
• Willingness to avoid pregnancy or fathering children.

Exclusion Criteria: 

• Prior receipt of a selective FGFR inhibitor in the past 6 months. 
• Receipt of anticancer medications or investigational drugs for any indication or reason within 28 days before first dose of pemigatinib. 
• Cannot be a candidate for potentially curative surgery. 
• Current evidence of clinically significant corneal or retinal disorder as confirmed by ophthalmologic examination. 
• Radiation therapy administered within 2 weeks of enrollment/first dose of study treatment.
• Untreated brain or central nervous system (CNS) metastases or brain or CNS metastases that have progressed (e.g., evidence of new or enlarging brain metastasis or new neurological symptoms attributable to brain or CNS metastases). 
• Known additional malignancy that is progressing or requires active treatment. 
• History of calcium and phosphate hemostasis disorder or systemic mineral imbalance with ectopic calcification of soft tissues.
• Clinically significant or uncontrolled cardiac disease. 
• Active chronic or current infectious disease requiring systemic antibiotic, antifungal, or antiviral treatment within 2 weeks before enrollment (participants with asymptomatic chronic infections on prophylactic treatment are allowed). 
• Evidence of active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection (defined as elevated transaminases or cirrhosis; chronic HBV/HCV infection with no cirrhosis and no elevated transaminases is allowed). 
• Known HIV infection. 
• Use of any potent CYP3A4 inhibitors or inducers or moderate CYP3A4 inducers within 14 days or five half-lives (whichever is longer) before the first dose of study drug/treatment. 
• Women who are pregnant or breastfeeding.