Shares in Wyeth have fallen 8% after the firm posted flat profits for the third quarter and warned of regulatory difficulties involving its much-touted investigational Alzheimer’s disease drug bapineuzumab.

Net income was $1.14 billion, while group sales were up 4% to $5.83 billion. Pharmaceutical revenues contributed $4.89 billion (+5%) and the most impressive performances came from the pneumococcal disease vaccine Prevnar, which grew 13% to $717 million, and the arthritis and psoriasis therapy Enbrel (etanercept), which jumped 32% to $697 million (excluding the USA and Canada, where it is co-marketed with Amgen). Wyeth’s best-seller continues to be the antidepressant Effexor (venlafaxine), which rose 3% to $982 million.

The firm’s Premarin (conjugated oestrogens) range of hormone replacement therapies fell 8% to $262 million, while the antibiotic Zosyn (piperacillin/tazobactam) climbed 7% to $305 million.

As for the antiulcerant Protonix, sales sank 45% to $234 million as a result of ‘at risk’ generic launches in the USA by Teva and Sun Pharmaceutical Industries. The New Jersey-based firm launched its own copy of Protonix which brought in $142 million of that total.

The company revised its earnings guidance from a previous estimate of $3.47-$3.55 per share to $3.49-$3.55 and chief executive Bernard Poussot said that "in a tough economy, Wyeth delivered a solid quarter". Wyeth also noted that it took a $68 million pre-tax charge in the quarter because of investments that have gone down the pan in Lehman Brothers and Washington Mutual.

However much attention focused on the announcement that the company is facing a delay enrolling patients in two late-stage European trials of bapineuzumab, which is partnered with Ireland’s Elan Corp. After a mixed set of Phase II study results raised questions about safety and efficacy this summer, several European countries are reviewing the findings and the Phase III study design before allowing enrollment.

The studies are scheduled to begin in June next year but could now be delayed depending on how the discussions with European regulators go.