There is a glycoprotein globulin made naturally in the human body called Gc protein-derived macrophage activating factor, or GcMAF for short.
Recently, it's become one of those purported "miracle cures" for many things, most notably all forms of cancer and autism. It is also surrounded by conspiracy theories of the "big pharma" variety, and specifically regarding the death of an autism doctor, Jeff Bradstreet.
Naturally, I'm skeptical about this molecule's health benefits.
The best scientific information I could find about it was on ScienceBasedMedicine.org
The production of GcMAF can be blocked by an enzyme called Nagalase (alpha-N-acetylgalactosaminidase), produced by many cancers, which led to its first incarnation in quackery as a "cure" for many cancers by Bill Sardi (remember him?) and Timothy Hubbell, based on dubious science and a clinical trial that didn't show what its proponents claimed it did and was later retracted.
[Bradstreet's discovery of] elevated Nagalase activity in autistic children ... resulted in a paper based on 40 autistic children that [Bradstreet] published in Autism Insights in which he claimed to have found elevated Nagalase levels in autistic children that were reduced by injecting GcMAF. While it is possible that GcMAF injections could decrease Nagalase levels if they were pathologically elevated it just doesn’t seem particularly plausible. What GcMAF injections could theoretically do is simply bypass the activity of Nagalase (which, remember, blocks the production of GcMAF) and lead to increased GcMAF levels. And ultimately Bradstreet also claimed improvement in autistic symptoms. Of course, this was a single-arm uncontrolled study, so it's not particularly compelling evidence.
I don't particularly appreciate the tone and irreverence for a man who may have committed suicide or was murdered, but you have the claims made that GcMAF can effectively treat Cancer and Autism.
These claims are repeated more aggressively by Mike Adams of NaturalNews.com
Called, "GcMAF", this molecule has the potential to be a universal cancer cure for many people. It has also been shown to reverse signs of autism in the vast majority of patients receiving the treatment.
I want to be sure that prospective answers don't argue from a lack of evidence. I couldn't find much; Wikipedia mentions a few small scale studies that favor the treatment. It mentions a few others that were all retracted. The gold standard here would be a study that is not retracted that shows it doesn't work or isn't safe.