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This is duplicated text of a letter from Pfizer Canada Inc.
Contact the company for a copy of any references, attachments or enclosures.
September 10, 2007
Dear Health Care Professional,
Subject: Process-Related Impurity (ethyl methanesulfonate - EMS) in all strengths and formulations of VIRACEPT (nelfinavir mesylate)
Pfizer and Health Canada wish to notify you of the presence of low levels of ethyl methanesulfonate (EMS), a process-related impurity in VIRACEPT (nelfinavir mesylate) and to provide guidance on the use of VIRACEPT in patients, including pregnant women and pediatric patients.
EMS is a potential human carcinogen. Data from animal studies indicate that EMS is teratogenic, mutagenic and carcinogenic. However, no data from humans exists. Animal studies do not necessarily predict human risk.
Patients taking VIRACEPT should contact their physician for discussion of whether they should continue or be switched to other treatment. For patients without other reasonable treatment options, Health Canada and Pfizer agree that there remains a positive benefit/risk for continued use of VIRACEPT.
VIRACEPT was removed by Roche Ltd. from the European market in June 2007, due to detection of high levels of EMS in some product there. In the Canadian product (manufacturing source is different from that of the European formulations), the level of exposure is over 200 times less than that found in Europe.
The levels currently deemed acceptable for long-term exposure to EMS suggest a theoretical lifetime increased cancer risk in adults of less than 1 case per 100,000 patients exposed. While no data on the impact of high EMS levels in humans exist, estimates from in-vitro and animal data suggest that currently observed EMS levels in Canadian formulations may result in cancer risk in adults between 1 and 17 cases per 100,000 patients exposed for a lifetime. Current estimates of the background incidence of cancer in the HIV population are about 20 to 30 cases per 1000 patient-years. Toxicology experts generally agree that the lifetime risk associated with exposure to a carcinogen is about 3-fold greater among pediatric patients between 2 and 16 years of age, and even higher among pediatric patients younger than 2 years of age.
Pfizer is working with Health Canada to prospectively limit EMS levels in VIRACEPT while still considering the immediate needs of patients on therapy. Further relevant information will be provided as it becomes available.
Healthcare professionals and patients who have additional questions may contact Pfizer Canada's medical information line at 1-800-463-6001.
Managing marketed health product-related adverse reactions depends on health care professionals and consumers reporting them. Reporting rates determined on the basis of spontaneously reported post-marketing adverse reactions are generally presumed to underestimate the risks associated with health product treatments. Any case of serious adverse reactions in patients receiving VIRACEPT should be reported to Pfizer Canada Inc. or Health Canada at the following addresses:
Sincerely,
original signed by
Dr Bernard Prigent
Vice-President and Medical Director
Pfizer Canada Inc.