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".
Taking an injectable blood-product of unknown source is particularly dangerous, as it could provide route for serious/deadly infectious diseases. The Medicines and Healthcare Products Regulatory Agency (MHRA) raided an "Immuno Biotech" 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". Subsequently the CEO of Immuno Biotech, David Noakes, received a jail-sentence for "supplying and selling an unlicensed medicine" and "money laundering". 
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.