Lonsurf®

Lonsurf^® is comprised of two active ingredients: trifluridine (a nucleoside metabolic inhibitor) and tipiracil (a thymidine phosphorylase inhibitor). The tablets come in strengths expressed in milligrams of trifluridine/tipiracil: i.e. 15/6.14mg or 20/8.19mg.

Currently, Lonsurf^® is indicated for the treatment of adult patients with metaic colorectal cancer. It is not on the Pharmaceutical Benefits Scheme (PBS) as yet and is available to people who have been previously treated with or cannot tolerate fluoropyrimidine, oxaliplatin and irinotecan chemotherapies, anti-vascular endothelial growth factor (VEGF) and anti-epidermal growth factor receptor (EGFR) agents with a private prescription.

Trifluridine is incorporated into replicating DNA strands where it inhibits DNA synthesis and prevents cell proliferation. However, trifluridine is rapidly metabolised by the enzyme thymidine phosphorylase. It is therefore formulated with tipiracil to prevent its rapid metabolism.

Adverse effects associated with Lonsurf^® include fatigue, dizziness, malaise and dyspnoea. Patients should be cautioned not to drive if dizziness or fatigue are experienced. Bone marrow suppression and gastrointestinal toxicity (e.g. diarrhoea, nausea and vomiting) were of most significance. Due to myelosuppression (anaemia, neutropenia, leucopenia, thrombocytopenia), complete blood cell counts are mandatory prior to starting treatment and are to be monitored throughout treatment.

Dosing of Lonsurf^® is based on body surface area. The recommended starting dose, based on the trifluridine component, is 35 mg/m²/dose. This dose should be administered twice daily on Days 1 to 5 and Days 8 to 12 of each 28-day cycle. A dosing calendar is available for patients to prevent confusion. Treatment should continue as long as benefit is observed or until unacceptable toxicity occurs. Tablets should be taken with food or within one hour after a meal. Patients and healthcare professionals should wash their hands after handling tablets.

Dosing considerations:

• Maximum dose of 80mg/dose
• The absolute neutrophil count (ANC) must be >1.5 ×10⁹ /L to initiate therapy
• Platelet count must be >75× 10⁹ /L to initiate
• Minimum dose of 20mg/m² twice daily
• After any dosage reductions, dose may not be re-escalated
• Patients with moderate renal dysfunction should be monitored closely for haematological toxicity. They do not require lower starting doses, although dose adjustment may be required throughout therapy. Patients with severe renal dysfunction were not studied. This medication is not recommended to be administered to these patients due to the lack of data.

The product information should be consulted for more detailed information.