In sum, Dr. Levy notes, the Massa chusetts mass screening program has tested for and diagnosed 16 types of metabolic errors. At one extreme, rapidly lethal maple sirup urine dis ease has been found once in 330,000 births, while at the other extreme, nonfatal but debilitating PKU has been found once in 14,000 births. Problems. Even when the screening program detects a metabolic defect, there remain two unsolved problems: How long treatment is necessary, and what can be done about pregnan cies of phenylketonuric women. PKU and other amino acidurias (difficul ties in metabolizing amino acids) usually express themselves in mental retardation, says Dr. Robert Guthrie, State University of New York (SUNY), Buffalo. Chronically high phenylalanine concentrations, for ex ample, compete with other amino acids and interfere with brain pro tein synthesis. Treatment is a low phenylalanine diet. Pregnant phenylketonuric women pass their high phenylalanine levels to the fetus, causing what is called maternal PKU and affecting not only the brain but also other organ sys tems. Microcephaly (small heads) and congenital heart disease can re sult. Automation. To carry out the largescale tests mass screening involves, increased automation of test proce dures will be necessary (C&EN, June 15, 1970, page 47). One step in this direction is development of an auto mated sampling machine—the "Phil lips machine"—named for its manu facturer, Robert Phillips, president of Fundamental Products Co., North Hollywood, Calif. This machine can now be adapted to preparing samples for thin-layer chromatography (TLC), according to conferee Michael Garrick, SUNY-Buffalo. Before use of the Phillips machine, blood samples are placed on filter pa per and dried. Investigators find, Dr. Gar rick notes, that amino acid con tent and even enzyme activity survive drying. The machine punches 7» inch-diameter circles from the filter paper and distributes the circles in specified numbered order into test trays for subsequent TLC or other analysis. In general, chemical reagent and in strument manufacturers look for real growth in the clinical field with the proliferation of mass screening pro grams. For example, president Al bert L. Baldock of J. T. Baker Chem ical Co. envisions reagent chemical sales to the clinical market growing by 12 to 15% yearly, based on antici pated increases in mass screening.
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Rifampicins tested against leukemia Derivatives of rifampicin, an anti biotic, are being actively investigated in several laboratories for their abil ity to inhibit enzymes found in lymph ocytes from the blood of human leu kemia patients (C&EN, Dec. 7, 1970, page 46). Some of the derivatives also exhibit varying degrees of effective ness against similar enzymes—ribonu cleic acid (RNA)-dependent deoxynucleic acid (DNA) polymerases—found in some viruses that induce tumors in animals (C&EN, Feb. 8, page 47). Rifampicin and its derivatives are products of research by Prof. Piero Sensi at Gruppo Lepetit, S.p.A., Milan, Italy. Lepetit is partly owned by Dow Chemical Co. Rifampicin is a synthetic derivative of rifamycin, a naturally occurring antibiotic. In 1957, Lepetit scientists isolated Streptomyces mediterranei bacteria from a red soil sample collected near Saint Raphael in southern France. This microorganism was found to produce a mixture of five related antibiotics, named rifamycins by Lepetit scien tists. The first antibiotic in this series to be employed on a large scale, in 1962, was rifamycin SV, for treatment of gram-positive bacterial, biliary, and tubercular infections. Advantages. Subsequent research on rifamycin SV was directed toward obtaining—by chemical modifica tion of its structure—a derivative of fering improved properties, such as prolonged retention in the body, high blood levels following oral adminis tration, and, particularly, greater ac tivity in gram-negative and tubercular infections. Prof. Sensi synthesized 3-formylrifamycin, enabling preparation of sev eral high-activity antibiotics. Rifam picin had the best properties. Rifampicin, a 3-(4-methyl-l-piperazinyliminomethyl) derivative of ri famycin SV, has broad antibacterial action, does not give cross resistance with any other antibiotic in current use, and is particularly effective in treatment of tuberculosis. It also kills leprosy bacteria—which are sim ilar to tuberculosis bacteria—whereas other antileprosy drugs only inhibit bacterial growth. Antiviral. In 1969, virologists in Is rael and the U.K. discovered that ri fampicin inhibits in vitro growth of certain animal viruses. This inhibi tion runs counter to action of most other antibiotics, which are effective only against bacteria. During the same year, Swiss scientists found that rifampicin also seemed to inhibit the
Lepetlt's Sensi
ability of a virus to transform a normal cell into a cancerous one. Lepetit's Bovisa Research Center in Milan synthesized various rifampicin derivatives and made them available to scientists in several countries. In 1970, U.S. scientists discovered an en zyme in some tumor-producing viruses that permits viral RNA to direct the synthesis of DNA in infected animal cells. Dr. Maurice Green, director of the institute of molecular virology at St. Louis University, St. Louis, Mo., has been testing numerous rifampi cin derivatives for activity against RNA-dependent DNA polymerase. One of the strongest inhibitors tested is 4-A^-benzyl-N-demethylrifampicin. When Dr. Robert C. Gallo and his coworkers at National Cancer Insti tute, Bethesda, Md., found evidence for RNA-dependent DNA polymerases in cells from leukemia patients, Dr. Green suggested tests of the isolated enzymes with rifampicin and deriva tives. Although there is no evidence for viral origin of the leukemia en zyme, Dr. Gallo found Af-demethylrifampicin to be effective against the enzyme. He is continuing to test an extensive series of rifampicin deriva tives for inhibitory activity. Accord ing to a Lepetit spokesman, 2,6-dimethyl - 4 - Af-benzyl-N-demethylrif ampicin is another inhibitor found effective in Dr. Gallo's laboratory. The National Cancer Institute plans to test a large number of compoundsmany related to rifampicin—for activ ity against leukemia and other forms of cancer. Tests will be run on iso lated DNA polymerase enzymes in test tubes, on cell cultures, and on lab animals. Simultaneously, Lepetit scientists will try to synthesize more active rifampicin derivatives. MARCH 8, 1971 C&EN 51
