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Fluorouracil · Efudex, Tolak

Small molecule · Antagonist of thymidylate synthase (TYMS) · developed by Hill Dermaceuticals

Approved FDA, Sep 2015

21 Registered trials

What is Fluorouracil?

Fluorouracil is a fluoropyrimidine antimetabolite nucleoside analog. Its metabolites inhibit thymidylate synthase, depleting thymidine triphosphate needed for DNA synthesis, and incorporate into RNA to disrupt RNA processing. It is studied in gastrointestinal, lung, head and neck, pancreatic and other solid tumors, including colorectal and gastric cancers.

Summary written with AI from the sources listed at the end of this page.

At a glance

Also known as: Efudex, Tolak, 5-FU
Drug type: Small molecule
Targets: thymidylate synthase (TYMS)
Mechanism: Antagonist of thymidylate synthase (TYMS)
Pathways: DNA synthesis, RNA processing
Therapy area: Oncology
Developer: Hill Dermaceuticals
In trials of: ALXO, AZN, BLRX, BNTX, CHRS, CMPS, CMPX, ELVN, GALT, GMAB
FDA status: Approved as Efudex, Tolak (September 18, 2015), NDA022259 · FDA label

✅ FDA-approved uses

Actinic keratosis (Tolak)
Superficial basal cell carcinoma (Fluorouracil)

From the indications section of the FDA label (version of Sep 6, 2022). Read the full label for the exact wording, limitations and safety information.

🧪 Clinical trials

Trial	Phase	Condition	Status	Sponsor
NCT07775287	Phase 3	Colorectal Cancer	Recruiting	GMAB
NCT06997497	Phase 3	Colon Adenocarcinoma	Recruiting	MRK
NCT05152147	Phase 3	Gastric Neoplasms	Active not recruiting	JAZZ
NCT07662031	Phase 2	Colorectal Cancer	Not yet recruiting	CMPS
NCT07290985	Phase 2	Gastroesophageal Adenocarcinoma	Recruiting	JAZZ
NCT06109467	Phase 2	GastroEsophageal Cancer	Active not recruiting	PBYI
NCT06219941	Phase 2	Gastric Cancer	Recruiting	AZN
NCT05382442	Phase 2	Metastatic Colorectal Cancer	Active not recruiting	SMMT
NCT04390399	Phase 2	Pancreatic Cancer	Active not recruiting	IBRX
NCT04083599	Phase 1/2	Malignant Solid Tumor	Active not recruiting	BNTX
NCT03169790	Phase 1/2	Non Hodgkin Lymphoma	Withdrawn	IBRX
NCT03281369	Phase 1/2	Gastric Adenocarcinoma or Gastroesophageal Junction Adenocarcinoma or…	Terminated	BLRX
NCT00388700	Phase 2	Colorectal Cancer	Withdrawn	GALT
NCT00386516	Phase 2	Cancer of the Bile Duct	Withdrawn	GALT
NCT00110721	Phase 2	Colorectal Cancer	Terminated	GALT
NCT06657144	Phase 1	Metastatic Solid Tumor	Recruiting	CHRS
NCT06328738	Phase 1	HER2-positive Breast Cancer	Active not recruiting	ELVN
NCT06057038	Phase 1	Malignant Solid Tumor	Active not recruiting	BNTX
NCT03013218	Phase 1	Metastatic Cancer	Completed	ALXO
NCT02620423	Phase 1	Pancreatic Adenocarcinoma	Completed	ONCY
NCT01274624	Phase 1	KRAS Mutant Metastatic Colorectal Cancer	Completed	ONCY

Trials of the companies BioRadar tracks, from ClinicalTrials.gov, most advanced phase first.

Conditions studied

Biliary Tract CancerColorectal Cancer (CRC)Esophageal AdenocarcinomaGastric CancerGastric NeoplasmsGastroesophageal AdenocarcinomaGastroEsophageal CancerGastroesophageal Junction CancerHead and Neck Squamous Cell Carcinoma (HNSCC)Malignant Solid TumorMelanomaMetastatic Colorectal CancerNon-Small Cell Lung Cancer (NSCLC)Pancreatic Cancer

Other drugs acting on TYMS

Capecitabine FDA approved Trifluridine and Tipiracil FDA approved

Sources

Updated Oct 11, 2026.

Data: FDA (Drugs@FDA, Purple Book, DailyMed), NIH (NCI Thesaurus, GSRS, RxNorm), ClinicalTrials.gov • Informational purposes only, not medical or investment advice. • All drugs A–Z