The term “ laetrile ” is an acronym (laevorotatory and mandelonitrile) used to describe a purified form of the chemical amygdalin, a cyanogenic glucoside (a plant compound that contains sugar and produces cyanide) found in the pits of many fruits and raw nuts and in other plants such as lima beans, clover, and sorghum. Reviewed in [1-6] In the 1970s, laetrile gained popularity as an anticancer agent. By 1978, more than 70,000 individuals in the United States were reported to have been treated with it. Reviewed in [2,7,8] Laetrile has been used for cancer treatment both as a single agent and in combination with a metabolic therapy program that consists of a specialized diet, high-dose vitamin supplements, and pancreatic enzymes.[9] Reviewed in [10]

In the United States, researchers must file an Investigational New Drug (IND) application with the US Food and Drug Administration (FDA) to conduct drug research in human subjects. In 1970, an application for an IND to study laetrile was filed by the McNaughton Foundation (San Ysidro, California). This request was initially approved but later rejected because preclinical evidence in animals showed that laetrile was not likely to be effective as an anticancer agent, Reviewed in [3,11,12] and because there were questions about how the proposed study was to be conducted. Reviewed in [13] Laetrile supporters viewed this reversal as an attempt by the US government to block access to new and promising cancer therapies, and pressure mounted to make laetrile available to the public. Court cases in Oklahoma, Massachusetts, New Jersey, and California challenged the FDA’s role in determining which drugs should be available to cancer patients. Consequently, laetrile was legalized in more than 20 states during the 1970s. In 1980, the US Supreme Court overturned decisions by the lower courts, thereby reaffirming the FDA’s position that drugs must be proven to be both safe and effective before widespread public use. Reviewed in [2,14] As a result, the use of laetrile as a cancer therapy or as a treatment for any other medical condition is not approved in the United States, but the compound continues to be manufactured and administered as an anticancer therapy, primarily in Mexico. Inappropriate advertisement of laetrile as a cancer treatment has resulted in an FDA investigation that culminated in charges and conviction of one distributor.[15]

Although the names laetrile, Laetrile, and amygdalin are often used interchangeably, they are not the same product. The chemical composition of US-patented Laetrile (mandelonitrile-beta-glucuronide), a semisynthetic derivative of amygdalin, is different from the laetrile/amygdalin produced in Mexico (mandelonitrile beta-D-gentiobioside), which is made from crushed apricot pits. Reviewed in [16,17] Mandelonitrile, which contains cyanide, is a structural component of both products. Reviewed in [16] It has been proposed that cyanide is the active cancer-killing ingredient in laetrile, but 2 other breakdown products of amygdalin—prunasin (which is similar in structure to Laetrile) and benzaldehyde —may also be cancer cell inhibitors.[18-21] The studies discussed in this summary used either Mexican laetrile/amygdalin or the patented form. In most instances, the generic term “laetrile” will be used in this summary; however, a distinction will be made between the products when necessary.

Laetrile can be administered orally as a pill, or it can be given by injection (intravenous or intramuscular). It is commonly given intravenously over a period of time followed by oral maintenance therapy. The incidence of cyanide poisoning is much higher when laetrile is taken orally [22] Reviewed in [23,24] because intestinal bacteria and some commonly eaten plants contain enzymes (beta-glucosidases) that activate the release of cyanide after laetrile has been ingested. Reviewed in [18,23] Relatively little breakdown to yield cyanide occurs when laetrile is injected. Reviewed in [7,23] Administration schedules and the length of treatment in animal models and humans vary widely.

References

1. Howard-Ruben J, Miller NJ: Unproven methods of cancer management. Part II: Current trends and implications for patient care. Oncol Nurs Forum 11 (1): 67-73, 1984 Jan-Feb.  [PUBMED Abstract]
   
   
2. Curt GA: Unsound methods of cancer treatment. Princ Pract Oncol Updates 4 (12): 1-10, 1990. 
   
   
3. Dorr RT, Paxinos J: The current status of laetrile. Ann Intern Med 89 (3): 389-97, 1978.  [PUBMED Abstract]
   
   
4. Calabrese EJ: Possible adverse side effects from treatment with laetrile. Med Hypotheses 5 (9): 1045-9, 1979.  [PUBMED Abstract]
   
   
5. The laetrile controversy. In: Moss RW: The Cancer Industry: The Classic Expose on the Cancer Establishment. Brooklyn, NY: First Equinox Press, 1996, pp 131-52. 
   
   
6. Laetrile at Sloan-Kettering: a case study. In: Moss RW: The Cancer Industry: The Classic Expose on the Cancer Establishment. Brooklyn, NY: First Equinox Press, 1996, pp 153-86. 
   
   
7. Lerner IJ: Laetrile: a lesson in cancer quackery. CA Cancer J Clin 31 (2): 91-5, 1981 Mar-Apr.  [PUBMED Abstract]
   
   
8. Ellison NM, Byar DP, Newell GR: Special report on Laetrile: the NCI Laetrile Review. Results of the National Cancer Institute's retrospective Laetrile analysis. N Engl J Med 299 (10): 549-52, 1978.  [PUBMED Abstract]
   
   
9. Moertel CG, Fleming TR, Rubin J, et al.: A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med 306 (4): 201-6, 1982.  [PUBMED Abstract]
   
   
10. Ross WE: Unconventional cancer therapy. Compr Ther 11 (9): 37-43, 1985.  [PUBMED Abstract]
    
    
11. Lewis JP: Laetrile. West J Med 127 (1): 55-62, 1977.  [PUBMED Abstract]
    
    
12. Unproven methods of cancer management. Laetrile. CA Cancer J Clin 22 (4): 245-50, 1972 Jul-Aug.  [PUBMED Abstract]
    
    
13. Rosen GM, Shorr RI: Laetrile: end play around the FDA. A review of legal developments. Ann Intern Med 90 (3): 418-23, 1979.  [PUBMED Abstract]
    
    
14. Curran WJ: Law-medicine notes. Laetrile for the terminally ill: Supreme Court stops the nonsense. N Engl J Med 302 (11): 619-21, 1980.  [PUBMED Abstract]
    
    
15. U.S. Department of Justice, United States Attorney -- Eastern District of New York.: President of Queens Firm Found Guilty of Criminal Contempt For Violating Court Order Not to Market Bogus Cancer Cure Over the Internet. Rockville, Md: U.S. Food and Drug Administration, 2003. Available online. ¹ Last accessed May 2, 2006. 
    
    
16. Fenselau C, Pallante S, Batzinger RP, et al.: Mandelonitrile beta-glucuronide: synthesis and characterization. Science 198 (4317): 625-7, 1977.  [PUBMED Abstract]
    
    
17. Chandler RF, Anderson LA, Phillipson JD: Laetrile in perspective. Can Pharm J 117 (11): 517-20, 1984. 
    
    
18. Newmark J, Brady RO, Grimley PM, et al.: Amygdalin (Laetrile) and prunasin beta-glucosidases: distribution in germ-free rat and in human tumor tissue. Proc Natl Acad Sci U S A 78 (10): 6513-6, 1981.  [PUBMED Abstract]
    
    
19. Rauws AG, Olling M, Timmerman A: The pharmacokinetics of prunasin, a metabolite of amygdalin. J Toxicol Clin Toxicol 19 (8): 851-6, 1982.  [PUBMED Abstract]
    
    
20. Kochi M, Takeuchi S, Mizutani T, et al.: Antitumor activity of benzaldehyde. Cancer Treat Rep 64 (1): 21-3, 1980.  [PUBMED Abstract]
    
    
21. Kochi M, Isono N, Niwayama M, et al.: Antitumor activity of a benzaldehyde derivative. Cancer Treat Rep 69 (5): 533-7, 1985.  [PUBMED Abstract]
    
    
22. Gostomski FE: The effects of amygdalin on the Krebs-2 carcinoma and adult and fetal DUB(ICR) mice. [Abstract] Diss Abstr Int B 39 (5): 2075-B, 1978. 
    
    
23. Herbert V: Laetrile: the cult of cyanide. Promoting poison for profit. Am J Clin Nutr 32 (5): 1121-58, 1979.  [PUBMED Abstract]
    
    
24. Viehoever A, Mack H: Bio-chemistry of amygdalin (bitter, cyanogenetic principle from bitter almonds). Am J Pharm 107(Oct): 397-450, 1935. 
    
    

Glossary Terms

A substance found in the pits of many fruits such as apricots and papayas, and in other foods. It has been tried in some countries as a treatment for cancer, but it has not been shown to work in clinical studies. Amygdalin is not approved for use in the United States. Also called laetrile.

An animal with a disease either the same as or like a disease in humans. Animal models are used to study the development and progression of diseases and to test new treatments before they are given to humans. Animals with transplanted human cancers or other tissues are called xenograft models.

A large group of single-cell microorganisms. Some cause infections and disease in animals and humans. The singular of bacteria is bacterium.

A colorless oily liquid used as a flavoring agent and to make dyes, perfumes, and pharmaceuticals. Benzaldehyde is chemically related to benzene.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

A plant compound that contains sugar and produces cyanide.

In chemistry, a compound produced from or related to another.

A protein that speeds up chemical reactions in the body.

FDA. An agency in the U.S. federal government whose mission is to protect public health by making sure that food, cosmetics, and nutritional supplements are safe to use and truthfully labeled. The Food and Drug Administration also makes sure that drugs, medical devices, and equipment are safe and effective, and that blood for transfusions and transplant tissue are safe. Also called FDA.

Taking into the body by mouth.

Use of a syringe and needle to push fluids or drugs into the body; often called a "shot."

Having to do with the intestines.

IM. Within or into muscle. Also called IM.

Into or within a vein. Intravenous usually refers to a way of giving a drug or other substance through a needle or tube inserted into a vein. Also called I.V.

In clinical trials, refers to a drug (including a new drug, dose, combination, or route of administration) or procedure that has undergone basic laboratory testing and received approval from the U.S. Food and Drug Administration (FDA) to be tested in human subjects. A drug or procedure may be approved by the FDA for use in one disease or condition, but be considered investigational in other diseases or conditions. Also called experimental.

A substance found in the pits of many fruits such as apricots and papayas, and in other foods. It has been tried in some countries as a treatment for cancer, but it has not been shown to work in clinical studies. Laetrile is not approved for use in the United States. Also called amygdalin.

Treatment that is given to help a primary (original) treatment keep working. Maintenance therapy is often given to help keep cancer in remission.

Treatment to correct changes in metabolism that can be caused by disease.

By or having to do with the mouth.

A protein secreted by the pancreas that aids in the digestion of food.

Research using animals to find out if a drug, procedure, or treatment is likely to be useful. Preclinical studies take place before any testing in humans is done.

Treatment.

A key nutrient that the body needs in small amounts to grow and stay strong. Examples are vitamins A, C, and E.