Researchers presenting data on Neoprobe Corp.'s RIGS product todiagnose colorectal cancer reported Friday that the systemsignificantly improved detection, which resulted in extended survival.

Results came from a multi-center Phase II trial with 104 evaluablepatients that ran from late 1992 to mid-1994. The trial enrolled bothprimary and recurrent colorectal patients who had no prior exposureto a murine antibody product.

The trial showed surgical decisions were changed for 64 percent ofthe patients who initially had their cancer detected by CT scan andtraditional surgical exploration. The RIGS (radioimmunoguidedsurgery) system identified additional tissue in 56 percent of the 75primary colorectal cancer patients and 66 percent of the 29 patientswith recurrent disease, reported John Daly, now with CornellUniversity Medical Center.

"The Phase II clinical results show that RIGS technology may be anextremely sensitive method for identifying diseased tissue that cannotbe identified by the surgeon's sight and touch or even CT[computerized tomography]," Daly said. As to the resulting changedsurgical decisions, he said, "Many of these changes impacted thecourse of the patients' treatment and the resulting improvements inpatient management may ultimately improve the prognosis for thesepatients."

Data were presented at The Society of Surgical Oncology's 48thAnnual Cancer Symposium in Boston.

David Bupp, Neoprobe's president, told BioWorld the resultsconfirm the company's belief that the product can benefit thediagnosis of cancer of the colon or rectum. "The results certainlyconfirm that RIGS is providing tremendous incremental informationfor the surgeon," he said.

RIGS currently is being tested in Phase III trials in the U.S. andEurope, in both primary and recurrent colorectal cancer. Bupp saidthe company is on track to enroll all 408 patients in the trials by theend of this month. "We would expect to file [for regulatory approval]late in the third quarter [of 1995] in Europe and probably early in thefirst quarter of 1996 in the U.S.," he said. Review is expected in thesecond half of 1996 in Europe and in the second half of 1997 in theU.S., he said.

The RIGS system for colorectal cancer uses a monoclonal antibodylabeled with Iodine-125. The antibody is injected, and designed toadhere to cancer cells or antigens. During surgery the RIGS gammadetector is used to search for radioactivity in specific tissues,indicating the presence of cancer.

Edward Martin Jr., of Ohio State University's Comprehensive CancerCenter, presented data at the symposium on long-term survival froman earlier RIGS study sponsored by the National Cancer Institute. Inone study involving 32 primary colorectal cancer patients, all 16 whohad RIGS-identified tissue removed survived at least three years. Butonly two of 16 survived who had RIGS-identified tissue that couldnot be removed.

Also, in a study involving 131 recurrent colorectal cancer patients, 30of 49 patients survived who had RIGS-identified tissue removed,while only one of 82 survived whose RIGS-positive tissue was leftafter surgery.

In the Phase II study, the RIGS system did not localize, or attach to atumor, in 9 percent of primary cases, but did in 100 percent ofrecurrent cases, Bupp said.

Bupp said the ongoing Phase III studies are designed in a similar wayas the Phase II studies, with similar endpoints: the ability of thesystem to provide incremental diagnostic information. "Based uponthe RIGS findings, we expect patients can be more accurately staged,and the RIGS system will allow them to make better surgical andclinical decisions."

Bupp said discussions with potential marketing partners in the U.S.and Europe have accelerated as marketers have become aware of theclinical information.

Even though the RIGS presentation wasn't made until after themarket closed Friday, news that the presentation was going to bemade has resulted in heavy trading of Neoprobe stock(NASDAQ:NEOP). On Thursday, the stock lost 13 cents in tradingof nearly 900,000 shares, compared to a daily average of about55,000 shares. The stock was up 31 cents Friday, at $4.19, in tradingof 260,000 shares.n

-- Jim Shrine

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