Merck Corrects Description of a Statistical Method Used in APPROVe Study; Study Results Unchanged

Business Wire, May 30, 2006

WHITEHOUSE STATION, N.J. -- Merck & Co., Inc. is correcting its prior description of one of the statistical methods used to analyze certain data in the APPROVe study published in 2005, and has notified the study authors, the New England Journal of Medicine (NEJM) and regulatory authorities. Merck recently discovered the need for this correction while reviewing the preliminary analyses of the off-drug extension data for the APPROVe study. Merck believes that this correction does not change the results of the APPROVe study, in which an increased relative risk for confirmed thrombotic cardiovascular events for VIOXX compared to placebo was observed beginning after 18 months of continuous daily treatment. This correction is unrelated to the recently announced preliminary analysis of the off-drug extension of the APPROVe study.

The VIOXX cardiovascular data analysis plan called for numerous statistical and graphical methods to be used to assess whether the relative risk of VIOXX compared to placebo was constant over time or if it changed over time (see attached). The use of the variable, logarithm of time, was an element in the primary method specified. The reference to logarithm of time in the description of methods published in the NEJM and submitted to regulatory agencies was in error. The reported result (p-value = 0.01) came from a statistical model using linear time, not logarithm of time. Recent tests show that the result using logarithm of time has a p-value = 0.07. The results of diagnostic steps specified in the data analysis plan indicate that the linear test is an appropriate method to assess changes in relative risk over time.

As specified in the analysis plan, Merck used additional analytical and graphical methods to evaluate whether the relative risk changed over time. These methods included a Kaplan-Meier plot that showed similar curves for placebo and VIOXX during the first 18 months, which then began to separate at approximately 18 months. Relative risks were also calculated over successive six-month intervals in the study. Over the 36-month period of the study, the relative risk was lowest in the first three sets of six-month intervals and highest in the last three sets of six-month intervals, again demonstrating changing relative risk over time. The results of the linear time analysis, the Kaplan-Meier plot, and the interval relative risks together confirm that the relative risk changes over time.

The linear time and logarithm of time analyses only test whether relative risk changes over time, they do not test the overall magnitude of relative risk. The overall magnitude of the relative risks and their associated p-values were described correctly.

Merck believes that today's correction does not change the results of the APPROVe study. Nonetheless, Merck intends to retain an independent statistical expert to review data and analyses from the APPROVe study. The study's authors advised Merck that they intend to submit a correction to the NEJM.

About the APPROVe Study

APPROVe (Adenomatous Polyp Prevention on VIOXX) was a multi-center, randomized, placebo-controlled, double-blind study designed to evaluate the efficacy of 156 weeks (three years) of treatment with VIOXX 25 mg in preventing recurrence of colorectal polyps in patients with a history of colorectal adenomas. There was no Statistical Analysis Plan (SAP) for the cardiovascular data from APPROVe alone. Merck planned to combine the cardiovascular data from APPROVe with data from two other placebo-controlled studies, VICTOR and ViP. Given the decision to stop the study early, the APPROVe data were analyzed separately.

About Merck

Merck & Co., Inc. is a global research-driven pharmaceutical company dedicated to putting patients first. Established in 1891, Merck currently discovers, develops, manufactures and markets vaccines and medicines to address unmet medical needs. The Company devotes extensive efforts to increase access to medicines through far-reaching programs that not only donate Merck medicines but help deliver them to the people who need them. Merck also publishes unbiased health information as a not-for-profit service. For more information, visit www.merck.com.

Forward-Looking Statement

This press release (including the attachment) contains "forward-looking statements" as that term is defined in the Private Securities Litigation Reform Act of 1995. These statements are based on management's current expectations and involve risks and uncertainties, which may cause results to differ materially from those set forth in the statements. The forward-looking statements may include statements regarding product development, product potential or financial performance. No forward-looking statement can be guaranteed, and actual results may differ materially from those projected. Merck undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events, or otherwise. Forward-looking statements in this press release should be evaluated together with the many uncertainties that affect Merck's business, particularly those mentioned in the cautionary statements in Item 1 of Merck's Form 10-K for the year ended Dec. 31, 2005, and in its periodic reports on Form 10-Q and Form 8-K, which the Company incorporates by reference.