[Vào đầu phần bàn luận, tác giả nhắc lại kết quả chính của nghiên cứu. Lúc nào cũng phải nhắc lại, vì độc giả có thể … quên.]

Our data show that, as compared with placebo or with other antidiabetic regimens, treatment with rosiglitazone was associated with a significant increase in the risk of myocardial infarction and with an increase in the risk of death from cardiovascular causes that was of borderline significance. [Nhấn mạnh rằng rosiglitazone có hại – kĩ thuật tuyên truyền một cách khoa học] The similar odds ratio for comparison with placebo suggests that the increased risk associated with rosiglitazone was not a function of the protective effects of active comparator drugs. [Nhưng nghiên cứu có vài hạn chế] However, these findings are based on limited access to trial results from publicly available sources, not on patient-level source data. Furthermore, results are based on a relatively small number of events, resulting in odds ratios that could be affected by small changes in the classification of events. [Mặc dù hạn chế nhưng kết quả này đáng quan tâm, vì tầm quan trọng của nó. Chú ý tác giả nhấn mạnh rằng kết quả có tầm y tế cộng đồng vì thuốc được nhiều người sử dụng] Nonetheless, our findings are worrisome because of the high incidence of cardiovascular events in patients with diabetes.4 Because exposure of such patients to rosiglitazone is widespread, the public health impact of an increase in cardiovascular risk could be substantial if our data are borne out by further analysis and the results of larger controlled trials.

[Đây là đoạn văn tác giả biện minh rằng kết quả đó có thể không phải do yếu tố ngẫu nhiên] Although we did not have access to the source data to construct a composite outcome that included myocardial infarction or death from cardiovascular causes, the increase in the odds ratios for both of these end points suggests that observed adverse effects associated with rosiglitazone were probably not due to chance alone. This meta-analysis included a group of trials that were of relatively short duration (24 to 52 weeks). The odds ratio for these shorter-term trials was similar to the overall results of the meta-analysis. Thus, in susceptible patients, rosiglitazone therapy may be capable of provoking myocardial infarction or death from cardiovascular causes after relatively short-term exposure. In contrast, long-term therapies that improve cardiovascular outcomes, such as statins and antihypertensive drugs, often take several years to provide benefits. Notably, the estimates for the odds ratios for myocardial infarction and death from cardiovascular causes appear elevated for rosiglitazone in comparison with placebo or other commonly prescribed antidiabetic therapies.

[Sau khi loại bỏ yếu tố ngẫu nhiên trong đoạn trên, tác giả luận bàn về cơ chế sinh học của rosiglitazone. Tại sao thuốc có hại cho sức khoẻ tim mạch?] The mechanism for the apparent increase in myocardial infarction and death from cardiovascular causes associated with rosiglitazone remains uncertain. One potential contributing factor may be the adverse effect of the drug on serum lipids. The FDA-approved rosiglitazone product label reports a mean increase in low-density lipoprotein (LDL) cholesterol of 18.6% among patients treated for 26 weeks with an 8-mg daily dose, as compared with placebo.25 In observational studies and lipid-lowering trials, elevated levels of LDL cholesterol were associated with an increase in adverse cardiovascular outcomes. Thus, an increase in LDL cholesterol of the magnitude observed in the rosiglitazone group may have contributed to adverse cardiovascular outcomes, although the rapidity and magnitude of the apparent hazard was not consistent with an effect produced by lipid changes alone.

[Lại thêm một bàn luận về cơ chế ảnh hưởng của rosiglitazone] Several other properties of rosiglitazone may contribute to adverse cardiovascular outcomes. Rosiglitazone and other thiazolidinediones are known to precipitate congestive heart failure in susceptible patients.26 Congestive heart failure is a physiological state that is associated with an increased intravascular volume. Volume overload increases stress on the left ventricular wall, a factor that determines myocardial oxygen demand. In susceptible patients, an increase in myocardial oxygen demand could theoretically provoke ischemic events. The administration of thiazolidinediones, including rosiglitazone, also produces a modest reduction in the hemoglobin level.25 In susceptible patients, a reduced hemoglobin level may result in increased physiological stress, thereby provoking myocardial ischemia. A study of rosiglitazone that was conducted in rats reported an increase in the rate of death after experimentally induced myocardial infarction.

[Bàn về các diễn giải khác] Rosiglitazone is not the first PPAR agonist that has been reported to increase adverse cardiovascular events. Muraglitazar, an investigational dual PPAR-α and PPAR-γ agonist, increased adverse cardiovascular events, including myocardial infarction, during phase 2 and 3 testing.28 After publication of an analysis of cardiovascular outcomes, muraglitazar was not approved by the FDA, and further development was subsequently halted by the manufacturer. Development programs for many other PPAR agonists have been terminated after evidence of toxicity emerged during preclinical studies or initial trials in humans. According to a former FDA official, more than 50 Investigational New Drug applications for novel PPARs have been filed, but no additional drugs have successfully reached the market in more than 6 years.29 In some cases, these drugs have failed because of evidence of direct myocardial toxicity in studies in animals,29 but few data on toxicity are available in the public domain because of the common industry practice of not publishing safety findings for failed products.

[Thêm một giả thuyết khác về cơ chế] PPAR agonists such as rosiglitazone have very complex biologic effects, resulting from the activation or suppression of dozens of genes.30 The patterns of gene activation or suppression differ substantially among various PPAR agonists, even within closely related compounds. The biologic effects of the protein targets for most of the genes influenced by PPAR agonists remain largely unknown. Accordingly, many different and seemingly unrelated toxic effects have emerged during development of other PPAR agents.29 Some drugs have provoked multispecies, multi–organ system cancers; others have resulted in rhabdomyolysis or nephrotoxicity.29 Troglitazone was withdrawn from the market for rare, but sometimes fatal, liver toxicity. Accordingly, it must be assumed that a variety of unexpected toxic effects are possible when PPAR agonists are administered to patients.

[Còn các thuốc khác trong nhóm thì sao?] The question as to whether the observed risks of rosiglitazone represent a “class effect” of thiazolidinediones must also be considered. Pioglitazone is a related agent also widely used to treat type 2 diabetes mellitus. However, unlike rosiglitazone, pioglitazone has been studied in a prospective, randomized trial of cardiovascular outcomes, called Prospective Pioglitazone Clinical Trial in Macrovascular Events (PROACTIVE).31 The primary end point, a broad composite that included coronary and peripheral vascular events, showed a trend toward benefit from pioglitazone (hazard ratio, 0.90; P=0.095). A secondary end point consisting of myocardial infarction, stroke, and death from any cause showed a significant effect favoring pioglitazone (hazard ratio, 0.84; P=0.027). Notably, pioglitazone appears to have more favorable effects on lipids, particularly triglycerides, than does rosiglitazone.

[Bàn về những điểm yếu của nghiên cứu] Our study has important limitations. We pooled the results of a group of trials that were not originally intended to explore cardiovascular outcomes. Most trials did not centrally adjudicate cardiovascular outcomes, and the definitions of myocardial infarction were not available. Many of these trials were small and short-term, resulting in few adverse cardiovascular events or deaths. Accordingly, the confidence intervals for the odds ratios for myocardial infarction and death from cardiovascular causes are wide, resulting in considerable uncertainty about the magnitude of the observed hazard. Furthermore, we did not have access to original source data for any of these trials. Thus, we based the analysis on available data from publicly disclosed summaries of events. The lack of availability of source data did not allow the use of more statistically powerful time-to-event analysis. A meta-analysis is always considered less convincing than a large prospective trial designed to assess the outcome of interest. Although such a dedicated trial has not been completed for rosiglitazone, the ongoing Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD) trial may provide useful insights.

[Dù có hạn chế, câu kết luận phải ấn tượng] Despite these limitations, our data point to the urgent need for comprehensive evaluations to clarify the cardiovascular risks of rosiglitazone. The manufacturer's public disclosure of summary results for rosiglitazone clinical trials is not sufficient to enable a robust assessment of cardiovascular risks. The manufacturer has all the source data for completed clinical trials and should make these data available to an external academic coordinating center for systematic analysis. The FDA also has access to study reports and other clinical-trial data not within the public domain. Further analyses of data available to the FDA and the manufacturer would enable a more robust assessment of the risks of this drug. Our data suggest a cardiovascular risk associated with the use of rosiglitazone. [Một câu khuyến cáo] Until more precise estimates of the cardiovascular risk of this treatment can be delineated in patients with diabetes, patients and providers should carefully consider the potential risks of rosiglitazone in the treatment of type 2 diabetes.