Fenbendazole vs Mbendazole vs Ivermectin in Cancer 

Fenbendazole and mebendazole are benzimidazole anthelmintic drugs used to treat parasitic worm infections. Here are the key points comparing their efficacy and safety based on the provided sources:

Efficacy Against Parasites

• Both fenbendazole and mebendazole were effective against developing muscle larvae of Trichinella spiralis in mice. Mebendazole was also effective against encysted muscle larvae, while fenbendazole failed to have any effect on this stage.
• Mebendazole showed partial activity against adult T. spiralis worms at 72 hours post-infection, while fenbendazole had no effect.
• Mebendazole was found to be ineffective against Onchocerca volvulus (river blindness) microfilariae and adult worms in a chimpanzee model, likely due to poor absorption.

Anti-Cancer Activity

• Mebendazole has shown potent anti-tumor effects on various human cancer cell lines both in vitro and in vivo. It induces mitotic arrest, apoptosis, and inhibits tumor growth in xenograft models of melanoma, adrenocortical carcinoma, glioblastoma, and colon cancer.
• Limited data suggests fenbendazole may also have anti-neoplastic activity in humans, but large-scale clinical evidence is lacking.

Safety and Toxicity

• Mebendazole is generally well-tolerated with a good safety profile when used at recommended anti-parasitic doses.
• Albendazole (a related benzimidazole) has higher toxicity, with myelosuppression being the main dose-limiting side effect at high doses used for anti-cancer treatment. Therefore, mebendazole is considered safer for repurposing as an anti-cancer agent.

In summary, while both drugs are effective against certain parasites, mebendazole appears to have better efficacy against some stages and species. Mebendazole also has more evidence supporting its anti-cancer potential with a favorable safety profile compared to related compounds like albendazole.