What is Mepact?
Mepact (mifamurtide) is a liposomal formulation of muramyl tripeptide phosphatidyl ethanolamine (MTP-PE). This is a synthetic analogue of muramyl dipeptide, the smallest natural immuno-adjuvant from the mycobacterium cell wall.1
Mepact is indicated in children, adolescents and young adults for the treatment of high-grade resectable non-metastatic osteosarcoma after macroscopically complete surgical resection. It is used in combination with post-operative multi-agent chemotherapy.2
How does it work?
Mepact has a different mechanism of action to chemotherapy. Mepact works by activating the host immune system to release inflammatory cytokines3 that in turn target micro-metastatic lung disease. Micro-metastatic lung disease is the primary cause of death in osteosarcoma.4
Mepact enters the macrophage where it is broken down to muramyl di-peptide (MDP), which then binds to the NOD-2 receptor.1,3 Intracellular pathways are activated3 which induce cytotoxic function1,5,6,7 and secretion of numerous cytokines and chemokines1,7,8 which along with other recruited and activated immune cells,1 directly affect the micro-metastases1,5 causing tumour cell apoptosis.1,7,8
Mepact: Mechanism of action 1,3,5-8
The development of Mepact included one of the world’s largest independent osteosarcoma studies:9-11
- 622 newly diagnosed patients with osteosarcoma, with resectable primary tumours and without metastases9,10
- Independently designed, funded and managed by the Children’s Oncology Group (a consolidation of the Children’s Cancer Group and the Pediatric Oncology Group)
This study was designed to answer whether the addition of Mepact to chemotherapy would improve outcome, measured as co-primary endpoints of overall survival and event-free survival.9,10