HUM-MOLGEN archive: ETHI: Multiplex screening

Genzyme, one of the most successful biotech companies, recently announced that they have developed, and are starting to commercially introduce a multiplex genetic screening assay. The tests are not limited to indentifying multiple mutations associated with a single disease: these are simultaneous tests of hundreds of people for multiple disease genes. A copy of Genzyme's press release is below. A number of other companies, most notably Affymetrix, are working on similar multiplex tests. One has to ask: 1) What is the major market for this incredibly powerful technology? Is it limited to insurance companies, employers, governments, armies and other institutions which wish to screen large numbers of people for many different predispositions? Or are there large numbers of people who wish to know which of many genetically mediated diseases or behaviors they or their children are likely to develop? 2) What enforceable safeguards or assurances of accuracy are there for each of these many proposed scans? Like many US biotech companies Genzyme is apparently taking the position that FDA approval of these tests is not required. Presumably the technology will be quickly exported and regulators in many countries will have to face these questions. 3) How will genetic counseling for so many diseases at once be handled? For that matter, how many physicians are sufficiently versed in genetics and many different diseases to provide competent advice? Comments are solicited. Hans Goerl ETHI editor ***************************************************************************** ********************** Wire Service: PR (PR Newswire) Date: Wed, Nov 8, 1995 GENZYME UNIT'S NEW TECHNOLOGY MAKES MORE GENETIC TESTS FEASIBLE CAMBRIDGE, Mass., Nov. 8 /PRNewswire/ -- Integrated Genetics has developed a new genetic diagnostic technology that can simultaneously analyze hundreds of patient DNA samples for the presence of more than a hundred mutations in a single test. To validate the technology, Integrated Genetics, a unit of Genzyme Corp.'s General Division (Nasdaq: GENZ), analyzed DNA samples from 500 patients for the presence of 106 different mutations on seven genes. The results of this research were presented last month at a meeting of the American Society of Human Genetics in Minneapolis. The new technology, called Multiple Allele-Specific Diagnostic Assay (MASDA), makes it technically feasible to conduct the complex analyses needed to assess genetic predisposition and diagnose a wide range of genetically influenced disorders, including cancer and cardiovascular disease. The MASDA technology is particularly powerful for these applications because it can analyze hundreds of mutations on one gene or across a number of genes acting in concert. MASDA brings together two capabilities that previously were mutually exclusive: the ability to test large numbers of samples cost- effectively and the ability to ask hundreds of complex genetic questions about each sample. Current diagnostic tests that are capable of analyzing large numbers of genetic mutations are expensive and time- consuming. "With MASDA, we have added a significant capability," said Elliott D. Hillback Jr., Integrated Genetics' president. "This technology is an answer to an existing need for a more powerful and efficient method of genetic diagnostic testing. And it is elegant in its simplicity." Even though MASDA can detect multiple mutations, Integrated Genetics will not test every patient sample for all mutations unless such analysis is requested by the patient's physician and meets other guidelines for responsible use of genetic testing. How MASDA Works. MASDA's benefit is inherent in its simple but powerful two-step approach to known mutation detection. In step one, individual samples of DNA from numerous patients are broken into fragments that might contain mutations of interest to the patients' physicians. The DNA fragments from each patient are placed in a unique location on a filter membrane. The membrane can hold samples from hundreds of patients. The membrane with the patient samples is incubated with a mixture of DNA probes, each of which is a strand of DNA that hybridizes, or binds, with a particular mutation. Patient samples possessing mutations can be identified because the DNA probes carry either a radioactive or a fluorescent label. At this point, all patients who do not test positive can be informed that they do not possess any of the mutations for which they were being tested. Eliminating the negative samples in this way produces considerable cost savings. In conventional testing methods, each of these samples would have to undergo tedious analysis before a negative result could be reported. In the second step, the positive samples are tested, using a modified DNA sequencing procedure, to determine which mutation is present in the patient sample. The part of the filter containing a positive sample is punched out of the filter and chemically treated to separate the DNA probe from the patient's DNA and break the probe into fragments. The probe fragments are placed on a gel in an electric field, which separates them by length. Radioactive isotopes attached to the DNA probes create a series of dark bars on photographic film placed over the gel. To the trained eye, the resulting unique band pattern reveals exactly which mutation the patient has. In addition to being able to identify multiple mutations to a single gene, MASDA can identify multiple genetic disorders within a single patient. For example, if a patient sample contains mutations for cystic fibrosis and Gaucher disease, the resulting band pattern will identify both mutations. "Theoretically, there is no limit to the number of mutations that we can identify with the MASDA technology," said Tony Shuber, inventor of the technology and senior research scientist at Integrated Genetics. "Until MASDA, there was no technology for DNA testing for known mutations that had the potential to meet the necessary complexity and accuracy requirements at a reasonable cost." Seeking Broad Applications. Integrated Genetics, the world's leading provider of genetic diagnostic services, plans to introduce MASDA into its clinical DNA lab in 1996. Integrated Genetics will also use MASDA in the company's research program on predispositional testing, which is developing methods for determining susceptibility to various cancers and other diseases with a complex genetic component. Commercialization of these predispositional tests will depend on development of adequate mutation data bases and counseling protocols. Additional potential applications of the MASDA technology include other types of DNA-based testing such as infectious disease diagnosis. Integrated Genetics is talking to potential partners about applying MASDA in these areas. Integrated Genetics has filed several patent applications that cover MASDA and associated technologies. One of the world's top five biotechnology companies, Genzyme focuses on developing innovative products and services for major unmet medical needs.