Last reviewed 2026-04-20 · How we verify

Camptosar (irinotecan)

Irinotecan and its metabolite SN-38 bind to the topoisomerase I-DNA complex, preventing DNA repair and causing double-strand breaks.

Camptosar (irinotecan) is a topoisomerase inhibitor, a small molecule drug developed by Pfizer Inc, used to treat various cancers including adenocarcinoma of the pancreas, metastasis from malignant tumors of the colon, and secondary malignant neoplasms of the pancreas. It was approved by the FDA in 1996 and is now off-patent with 23 generic manufacturers. Camptosar works by inhibiting the enzyme topoisomerase I, which is essential for DNA replication, thereby preventing cancer cell growth. The drug has a half-life of 9.0 hours and bioavailability of 8%. It is a commercial product with no active Orange Book patents.

At a glance

Mechanism of action

Irinotecan is a derivative of camptothecin that interacts with topoisomerase I, an enzyme that helps relieve torsional strain in DNA by creating reversible single-strand breaks. By binding to the topoisomerase I-DNA complex, irinotecan and its active metabolite SN-38 prevent the rejoining of these breaks, leading to double-strand DNA damage during replication, which mammalian cells cannot efficiently repair.

Approved indications

• Metastatic colorectal cancer

Boxed warnings

• WARNING FULL PRESCRIBING INFORMATION WARNING: DIARRHEA and MYELOSUPPRESSION Early and late forms of diarrhea can occur. Early diarrhea may be accompanied by cholinergic symptoms which may be prevented or ameliorated by atropine. Late diarrhea can be life threatening and should be treated promptly with loperamide. Monitor patients with diarrhea and give fluid and electrolytes as needed. Institute antibiotic therapy if patients develop ileus, fever, or severe neutropenia. Interrupt Irinotecan hydrochloride injection and reduce subsequent doses if severe diarrhea occurs. Severe myelosuppression may occur. WARNING: DIARRHEA and MYELOSUPPRESSION See full prescribing information for complete boxed warning . • Early and late forms of diarrhea can occur. Early diarrhea may be accompanied by cholinergic symptoms which may be prevented or ameliorated by atropine. Late diarrhea can be life threatening and should be treated promptly with loperamide. Monitor patients with diarrhea and give fluid and electrolytes as needed. Institute antibiotic therapy if patients develop ileus, fever, or severe neutropenia. Interrupt irinotecan hydrochloride injection and reduce subsequent doses if severe diarrhea occurs. • Severe myelosuppression may occur.

Common side effects

• Diarrhea
• Fatigue/asthenia
• Vomiting
• Nausea
• Stomatitis
• Pyrexia
• Decreased appetite
• Neutropenia
• Lymphopenia
• Sepsis
• Gastroenteritis
• Intravenous catheter-related infection

Drug interactions

• phenytoin
• ritonavir

Key clinical trials

• Erlotinib Hydrochloride and Irinotecan Hydrochloride in Treating Patients With Advanced Solid Tumors (PHASE1)
• A Study to Compare Sacituzumab Tirumotecan (MK-2870) Monotherapy Versus Treatment of Physician's Choice as Second-line Treatment for Participants With Recurrent or Metastatic Cervical Cancer (MK-2870-020/TroFuse-020/Gog-3101/ENGOT-cx20) (PHASE3)
• Dinutuximab With Chemotherapy, Surgery and Stem Cell Transplantation for the Treatment of Children With Newly Diagnosed High Risk Neuroblastoma (PHASE3)
• M6620 and Irinotecan Hydrochloride in Treating Patients With Solid Tumors That Are Metastatic or Cannot Be Removed by Surgery (PHASE1)
• Neoadjuvant mFolfirinox With or Without Preoperative Concomitant Chemoradiotherapy in Patients With Borderline Resectable Pancreatic Carcinoma (PANDAS-PRODIGE 44) (PHASE2)
• Combination Chemotherapy With or Without Temsirolimus in Treating Patients With Intermediate Risk Rhabdomyosarcoma (PHASE3)
• Risk-Based Therapy in Treating Younger Patients With Newly Diagnosed Liver Cancer (PHASE3)
• Testing the Addition of an Individualized Vaccine to Durvalumab and Tremelimumab and Chemotherapy in Patients With Metastatic Triple Negative Breast Cancer (PHASE2)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Camptosar CI brief — competitive landscape report
• Camptosar updates RSS · CI watch RSS
• Pfizer portfolio CI