Bristol-Myers Squibb Company announced new results of the Baraclude (entecavir) resistance monitoring programme, which found a continued low incidence of resistance in studies of nucleoside-naive chronic hepatitis B patients through four years of treatment (n=663). In the three nucleoside- naive studies analyzed, two patients, or less than one per cent, experienced virologic breakthrough due to Baraclude resistance through the third year, and no additional patients developed resistance in the fourth year. In lamivudine- refractory patients, virologic breakthrough due to Baraclude resistance occurred in 15 per cent (n=8/53) of patients during year four.

The study results were presented at the 42nd Annual Meeting of the European Association for the Study of Liver Diseases (EASL) in Barcelona, Spain.

Drug resistance occurs when a virus mutates to avoid the effects of the medication. This can make treatment of hepatitis B challenging, because it can decrease the efficacy of the current medication and may compromise future treatment options. To date, studies have shown that multiple mutations are required to develop Baraclude resistance.

"The low incidence of resistance seen in nucleoside-naive patients through four years of treatment reflects Baraclude's high barrier to resistance in this patient population," said Richard Colonno, Ph.D., vice president for virology drug discovery at Bristol-Myers Squibb.

More than 700 patients across six studies initiated therapy on Baraclude (entecavir) and were monitored for treatment response and resistance.

The year four analysis evaluated those patients who received treatment with Baraclude during the fourth year (n=120 for patients in nucleoside-naive studies and n=53 for patients in lamivudine-refractory studies). In this comprehensive analysis, all patients enrolled in Bristol-Myers Squibb clinical trials ETV-014, -015, -022, -027, -026 and -901 who experienced a virologic breakthrough (greater than or equal to one log increase in HBV DNA from nadir as measured by a common assay - polymerase chain reaction or PCR), or whose virus had not yet reached undetectable levels - a measurement of the levels of hepatitis B virus in the blood (HBV DNA levels >300 copies/mL by PCR assay) at weeks 48, 96, 144, 192 or end of dosing were sequenced to determine if any changes occurred in the genetic code of the virus that would result in resistance or loss of effectiveness of Baraclude.

Viral load reduction in chronic hepatitis B patients treated with Baraclude in nucleoside-naive and lamivudine-refractory studies was also evaluated.