ALICIA CHANG AP Science Writer LOS ANGELES (AP) — An experimental drug greatly increased the number of people who appear to be cured of hepatitis C infection, according to results of mid-stage testing. The findings also suggest the drug telaprevir, made by Vertex Pharmaceuticals Inc., which sponsored the two studies, can cut treatment time from one year to six months. However, those taking the drug reported more side effects including severe rash, nausea and anemia than those on standard treatment alone. Still, telaprevir and similar drugs that other companies are testing offer hope of a major advance against the disease, which afflicts about 3.2 million Americans and 180 million people worldwide. It is caused by a bloodborne virus that can lead to liver scarring or liver cancer. Treatment is aimed at helping the immune system eliminate the virus. Current therapy combines the drugs peginterferon and ribavirin, but less than half on it are cured. Telaprevir and similar drugs under development are a potential game-changer because they specifically attack the hepatitis C virus. In the two studies, roughly two-thirds given telaprevir with standard therapy for six months showed no signs of the virus after six months, which doctors considered being cured of the disease. That's compared to 40 to 50 percent on standard treatment alone. "We can now sit down with our patients and tell them that 2 of 3 patients can be cured with a 24-week course of therapy," said Dr. John McHutchison, a Duke University doctor who led one study and has consulted for Vertex, based in Cambridge, Mass. Telaprevir is in late-stage testing and is not available commercially; the company plans to seek government approval next year. Results were published in Thursday's New England Journal of Medicine. Hepatitis C is a huge and growing problem because for years there was no way to screen the blood supply for the virus. Infection often doesn't produce symptoms for many years, so many of these cases are just now being recognized even though they may stem from transfusions a decade or more ago. The virus is mainly spread through contact with the blood of an infected person. It can be contracted by sharing dirty drug needles, getting pricked with a hospital needle with infected blood or being born to an infected mother. About a quarter of people exposed to hepatitis C clear it out of their bodies without treatment. But the rest develop a lifelong infection that attacks their livers. There is no vaccine against hepatitis C. In one study of 250 people with chronic hepatitis C in the United States, 61 percent who took telaprevir with standard therapy for six months cleared the virus, compared with 41 percent on standard therapy alone. Among those who took the drug and standard therapy for a year, 67 percent had no signs of infection. However, twice as many on telaprevir stopped treatment because of side effects. In another study of 334 people in Europe, 69 percent on telaprevir and standard therapy for six months had undetectable virus levels compared with 46 percent on standard treatment alone. The European study was led by Dr. Christophe Hezode of Henri Mondor Hospital in France. Hezode has consulted for Swiss drug maker Roche, which makes peginterferon and ribavirin. Testing of even shorter treatment times did not show benefit in either study. "Telaprevir appears to be a material advance in the therapy of hepatitis C, beginning a new era of treatment," Dr. Jay H. Hoofnagle of the National Institute of Diabetes and Digestive and Kidney Diseases wrote in an accompanying editorial. Other doctors were more cautious. "The new drug does show promise. However, its side effects remain a concern," said Dr. James Ou, a hepatitis expert at the University of Southern California's Keck School of Medicine. Other companies developing similar drugs include Idenix Pharmaceuticals, Schering-Plough Corp. and InterMune Inc.