The first US trial involving women who claim to have developed breast cancer as a result of taking hormone replacement therapy has been scheduled for July 31.

The lawsuit will cite a number of manufacturers of HRT products, including Wyeth and Pfizer, according to lawfirm Morgan & Weisbrod, which is representing one of two ‘bellwether’ plaintiffs whose cases will be examined closely in the trial.

The lawsuits were filed in the wake of the Women’s Health Initiative study, which revealed health risks associated with long-term use of HRT products. The WHI suggested that Wyeth’s combination estrogen and progestin product Prempro was associated with a greater risk of breast cancer, stroke and heart disease, findings that were replicated in the UK's Million Women Study and spurred a dramatic fall-off in HRT product prescribing.

The suit is alleging that the manufacturers of HRT products suppressed evidence of their risks while over-stating their benefits. It accuses Wyeth in particular of illegally marketing Prempro as having cardiovascular benefits.

The trial will be heard in Little Rock, Arkansas, by District Judge William Wilson.

News of the trial date comes after a run of favourable verdicts for drugmakers fighting liability lawsuits. A few days ago Merck & Co won the fourth case to come to trial involving its painkiller Vioxx (rofecoxib), while Wyeth itself was recently victorious in a trial concerning alleged heart valve damage caused by its obesity drugs Redux/Pondimin.

Earlier this month, reports surfaced that the US Food and Drug Administration is planning to announce a proposed rule which would protect the pharmaceutical industry from liability litigation, by declaring that federally-approved drug labels pre-empt US state laws.