Pfizer distances Celebrex from COX-II safety concerns
pharmafile | October 7, 2004 | News story | |
Pfizer has restated the safety of its blockbuster arthritis pain drug Celebrex following the withdrawal of Merck's rival drug Vioxx because of increased risk of heart attack and stroke.
Merck's immediate withdrawal of its drug on 30 September has caught healthcare regulators and prescribers by surprise, and has also raised immediate questions about whether the increased risk is common to all the drugs in the class.
Pfizer has responded swiftly to the safety concerns by claiming Celebrex has not demonstrated the same increased risk, even when taken at higher than recommended doses.
The first COX-II to market in 1998, Celebrex represented a new generation of painkiller drugs promising pain relief as effective as traditional non-specific non-steroidal anti-inflammatory drugs (NSAIDs) without the gastrointestinal side-effects seen in the older drugs.
Vioxx's withdrawal could also represent a huge opportunity for Pfizer to claim the market share left by its rival's departure, Merck's drug earning $2.5 billion in 2003, just behind Celebrex on $2.7 billion.
Pfizer has used a number of large-scale studies to support its claim, including one of 54,000 elderly patients published in the journal Circulation as well as a recent FDA-sponsored study of 1.4 million patients which showed similar outcomes.
"Each COX-II inhibitor has a distinct chemical structure and we would not expect them to have the same side-effect profile," said Dr Joe Feczko, Pfizer president of worldwide development.
"The data we've accumulated over time demonstrate that Celebrex does not increase the risk of serious cardiovascular events in patients with arthritis and pain, even at higher than recommended doses."
Pfizer is seeking further indications for its blockbuster: three ongoing trials, involving about 6,000 patients, are testing the drug's effectiveness in treating Alzheimer's disease and colorectal cancer.
Two of the large placebo-controlled studies under way – one sponsored by the National Cancer Institute and the other by Pfizer – are designed to determine whether Celebrex reduces the recurrence of pre-cancerous polyps in patients who have previously had polyps removed.
A third placebo-controlled study examining Celebrex's potential to prevent or slow the progression of Alzheimer's disease, is sponsored by the National Institutes of Health and has enrolled about 2,400 patients over the past three years.
"It is important to note that Alzheimer's patients are typically elderly and therefore at higher risk for cardiovascular events," said Dr John Breitner of the Seattle VA and the University of Washington and Alzheimer's Disease Anti-Inflammatory Prevention Trial (ADAPT) study chair.
"To date we have seen no evidence that there is any increased cardiovascular safety risk among study patients," Dr Feczko concluded.
In the long-term, Vioxx's withdrawal could mean renewed regulatory scrutiny of the COX-II class, which has undergone a number of inquiries in Europe and the US.
This could add an element of uncertainty to the future of Pfizer's other approved COX-II, Bextra. Meanwhile, Merck's second generation COX-II Arcoxia is already available in Europe but is still awaiting clearance in the US, and is likely to face further delay following Vioxx's withdrawal.
Novartis' new entrant to the market, Prexige (lumiracoxib), is another COX-II which has failed to gain FDA approval at the first time of asking, despite receiving marketing clearance in the UK in September 2003.
Related links:
Markets stunned as Merck withdraws blockbuster Vioxx
Friday , October 01, 2004
