}} }} Laetrile (patented 1961) is a simpler semisynthetic
derivative of amygdalin. Laetrile is synthesized from amygdalin by hydrolysis. The usual preferred commercial source is from apricot kernels (
Prunus armeniaca). The name is derived from the words "
laevorotatory" (referring to the molecule's
stereochemistry) and "mandelonitrile" (the portion of the molecule from which cyanide is released by decomposition). A 500 mg laetrile tablet may contain between 2.5 and 25 mg of hydrogen cyanide. Like amygdalin, laetrile is hydrolyzed in the duodenum (alkaline) and the intestine (enzymatically) to D-
glucuronic acid and L-mandelonitrile; the latter hydrolyzes to benzaldehyde and hydrogen cyanide, that in sufficient quantities causes
cyanide poisoning. Claims for laetrile were based on three different hypotheses. One claimed that amygdalin was hydrolyzed to mandelonitrile, converted to a beta-glucuronide complex in the liver, then carried to cancer cells where it would release mandelonitrile and hydrogen cyanide. Mandelonitrile, however, dissociates to benzaldehyde and hydrogen cyanide, and cannot be stabilized by glycosylation. Finally, the third asserted that laetrile is the discovered vitamin B-17, further suggesting that cancer results from "B-17 deficiency". It postulated that regular dietary administration of this form of laetrile would, therefore, actually prevent all incidences of cancer. There is no evidence supporting this conjecture in the form of a physiologic process, nutritional requirement, or identification of any deficiency syndrome. The term "vitamin B-17" is not recognized as a valid vitamin or
micronutrient.
History of laetrile Early usage Amygdalin was first isolated in 1830 from bitter almond seeds (
Prunus dulcis) by
Pierre-Jean Robiquet and Antoine Boutron-Charlard.
Justus von Liebig and
Friedrich Woehler found three hydrolysis products of amygdalin: sugar, benzaldehyde, and hydrogen cyanide. Later research showed that
sulfuric acid hydrolyzes it into
D-glucose, benzaldehyde, and hydrogen cyanide; while
hydrochloric acid gives
mandelic acid, D-glucose, and
ammonia. In 1845, amygdalin was used as a cancer treatment in Russia, and in the 1920s in the United States, but it was considered too poisonous. and later marketed as laetrile for cancer treatment. Thereafter, 27 U.S. states legalized the use of amygdalin within those states.
Subsequent results In a 1977 controlled, blinded trial, laetrile showed no more activity than placebo. These mistakes were considered scientifically inconsequential, but
Nicholas Wade, in
Science, stated that "even the appearance of a departure from strict objectivity is unfortunate." The results from these studies were published all together. A 2015
systematic review from the
Cochrane Collaboration found: The authors also recommended, on ethical and scientific grounds, that no further clinical research into laetrile or amygdalin be conducted. Given the lack of evidence, neither the U.S. Food and Drug Administration nor the
European Commission has approved laetrile. The U.S.
National Institutes of Health evaluated the evidence separately and concluded that clinical trials of amygdalin showed little or no effect against cancer. For example, a 1982 trial by the
Mayo Clinic of 175 patients found that tumor size had increased in all but one patient. The authors reported that "the hazards of amygdalin therapy were evidenced in several patients by symptoms of cyanide toxicity or by blood cyanide levels approaching the lethal range." The study concluded, "Patients exposed to this agent should be instructed about the danger of cyanide poisoning, and their blood cyanide levels should be carefully monitored. Amygdalin (Laetrile) is a toxic drug that is not effective as a cancer treatment". Additionally, "No controlled clinical trials (trials that compare groups of patients who receive the new treatment to groups who do not) of laetrile have been reported." The FDA and AMA crackdown, begun in the 1970s, effectively escalated prices on the black market, played into the conspiracy narrative, and enabled unscrupulous profiteers to foster multimillion-dollar smuggling empires. Some American cancer patients have traveled to
Mexico for treatment with the substance, for example at the
Oasis of Hope Hospital in
Tijuana. The actor
Steve McQueen died in Mexico following surgery to remove a
stomach tumor, having previously undergone extended treatment for
pleural
mesothelioma—a cancer associated with
asbestos exposure—under the care of
William Donald Kelley, a de-licensed dentist and orthodontist who claimed to have devised a cancer treatment involving
pancreatic enzymes, 50 daily vitamins and minerals, frequent body shampoos, enemas, a specific diet, and laetrile. Laetrile advocates in the United States include
Dean Burk, a former chief chemist of the
National Cancer Institute cytochemistry laboratory, and national
arm wrestling champion Jason Vale, who falsely claimed that his
kidney and
pancreatic cancers were cured by eating apricot seeds. Vale was convicted in 2004 for, among other things, fraudulently marketing laetrile as a cancer cure. The court also found that Vale had made at least $500,000 from his fraudulent sales of laetrile. In New Zealand, laetrile was among the purported treatments for cancer promoted by
Milan Brych, who was later convicted of medical fraud. In the 1970s, court cases in several states challenged the FDA's authority to restrict access to what they claimed were potentially lifesaving drugs. More than twenty states passed laws making the use of laetrile legal. After the unanimous Supreme Court ruling in
United States v. Rutherford, which established that interstate transport of the compound was illegal, usage fell off dramatically. The FDA continues to seek jail sentences for vendors marketing laetrile for cancer treatment, calling it a "highly toxic product that has not shown any effect on treating cancer." == See also ==