GcMAF (Gc protein-derived macrophage activating factor) is a blood product which proponents claim can cure cancer, HIV, autism and chronic fatigue syndrome. Cancer Research UK have described it as "scientifically extremely dubious".
As an injectable blood product of unknown source taking this is particularly stupid. The Medicines and Healthcare Products Regulatory Agency (MHRA) raided a factory in Cambridgeshire, England and found it was being made from blood plasma labelled "Not to be administered to humans or used in any drug products".
James Jeffrey Bradstreet, a US doctor who sold this as an autism cure committed suicide three days after being searched by the US authorities over this stuff. Supporters have claimed he was killed by Big Pharma.