The Cardiovascular Safety of Diabetes Drugs — Insights from the Rosiglitazone Experience.


The management of type 2 diabetes has been challenged by uncertainty about possible cardiovascular effects related to treatment intensity and choice of drug. Although the Food and Drug Administration (FDA) considers a decrease in glycated hemoglobin an approvable end point, very intensive glycemic control is associated with increased cardiovascular and all-cause mortality.1 The safety of specific drugs for type 2 diabetes — particularly the thiazolidinediones — has also been questioned. After rosiglitazone had been approved in the United States in 1999 and in Europe in 2000, a highly publicized meta-analysis in 2007 reported a 43% increase in myocardial infarction (P=0.03) and a 64% increase in death from cardiovascular causes (P=0.06).2 This report and subsequent FDA advisory committee reviews led to a boxed warning of myocardial ischemia in 2007 and highly restricted access to rosiglitazone in 2010. In 2010, the FDA placed a full clinical hold on the Thiazolidinedione Intervention with Vitamin D Evaluation (TIDE) trial (ClinicalTrials.gov number, NCT00879970), a large cardiovascular-outcome trial designed to evaluate the benefit of rosiglitazone and pioglitazone as compared with placebo (superiority hypothesis) and the safety of rosiglitazone as compared with pioglitazone (noninferiority hypothesis). In part owing to the rosiglitazone experience, the FDA issued an updated Guidance for Industry in 2008 requiring that preapproval and postapproval studies for all new antidiabetic drugs rule out excess cardiovascular risk, defined as an upper bound of the two-sided 95% confidence interval for major adverse cardiovascular events (MACE) of less than 1.80 and less than 1.30, respectively.3 Regardless of the presence or absence of preclinical or clinical signals of cardiovascular risk, the guidance has been applied broadly to all new diabetes drugs, creating substantial challenges in the drug development and approval process.

On June 5 and 6, 2013, the FDA held a joint meeting of the Endocrinologic and Metabolic Drugs Advisory Committee (on which we serve) and the Drug Safety and Risk Management Advisory Committee to further evaluate the cardiovascular safety of rosiglitazone. When rosiglitazone was approved in Europe, the European Medicines Agency raised concern about the cardiovascular risks of the thiazolidinedione class, including fluid retention, heart failure, and increased levels of low-density lipoprotein cholesterol. This concern led to a postmarketing requirement that cardiovascular-outcome trials be conducted for both pioglitazone and rosiglitazone, and these were reviewed at subsequent FDA meetings. Although the results of the Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD) study (NCT00379769) did not suggest an increased risk of MACE,4issues with trial design and data integrity led the FDA to require the sponsor to perform an independent readjudication of the data. This extensive exercise, performed by the Duke Clinical Research Institute, had a minimal effect on the overall point estimates and confidence intervals for MACE, which remained at less than 1.30. The result was consistent with the FDA guidance and provided reassurance that rosiglitazone was not associated with excess cardiovascular risk.

Two groups of authors (Scirica et al. and White et al.) now report in the Journal the results of large, placebo-controlled, cardiovascular-outcome trials, these involving saxagliptin and alogliptin, members of the incretin drug class. Neither of these drugs had shown increased cardiovascular risk in its development program. Both trials were designed to first rule out excess cardiovascular risk by means of noninferiority testing; if that was shown, superiority testing followed, on the assumption that better glycemic control might yield cardiovascular benefit. Both trials clearly met the FDA 2008 guidance for cardiovascular safety, but neither showed a reduction in cardiovascular events. Saxagliptin was associated with an unexpected increased risk of hospitalization for heart failure and a high frequency of hypoglycemia. Neither trial showed any increased risk of pancreatic adverse events, including cancer.

Before rosiglitazone, the cardiovascular safety of diabetes drugs had not been well studied. The initial concern with rosiglitazone arose from observational and case–control epidemiologic studies that generated a legitimate signal of possible cardiovascular harm, but every study had substantial methodologic shortcomings, including multiplicity, which meant that a statistically positive finding might be a false positive result.5 Meta-analyses were also performed with preapproval studies that had been designed to show a positive glycemic effect as the primary end point. These studies enrolled patients at low cardiovascular risk, were short in duration, used both placebo and active controls, and did not prospectively adjudicate cardiovascular safety events. In such situations, comparison of a new drug with an active agent is challenged by the uncertain cardiovascular risk of the active comparator. In contrast, a placebo-controlled design may lead to imbalances in background therapy (as was the case with saxagliptin) that could influence the cardiovascular outcomes. Meta-analyses of these premarketing trials from phase 3 development programs were therefore relatively insensitive in assessing cardiovascular risk, making dedicated postmarketing cardiovascular-outcome trials such as the RECORD study necessary to substantiate any risk signals. But the design of the RECORD study had substantial limitations that precluded a complete assessment of the cardiovascular safety of rosiglitazone.

In 2010, the FDA took a cautious stance and limited exposure to rosiglitazone, given the numerous alternative therapies that were available. But this position did not acknowledge the uncertainty of cardiovascular risk associated with other diabetes drugs on the market, and the FDA decision may have had unintended consequences. The intense publicity about the ischemic cardiac risk of rosiglitazone may have diverted attention from the better-established risk of heart failure that is common to the drug class. Restricted access led patients to switch from rosiglitazone to other diabetes drugs of unproven cardiovascular safety. Patients who had a myocardial infarction while taking rosiglitazone may have concluded that the drug was the cause, adversely affecting their perceptions of their doctor, drug companies, and the FDA. And placing a hold on the TIDE trial, although arguably justifiable, prevented any further clarification of the cardiovascular risks or benefits of the thiazolidinedione drug class. The rosiglitazone experience also raises the question of how to define a regulatory standard for withdrawing drugs from the market. New drug approvals are based on “substantial evidence” of drug safety and efficacy. But there is little guidance on what constitutes substantial evidence of harm that is sufficient to justify market withdrawal or the imposition of severe market restrictions.

What have we learned from the rosiglitazone experience? Clearly, the presumed cardiovascular risks of rosiglitazone led to a major change in FDA policy regarding the approval of all new diabetes drugs. From a cardiovascular perspective, rosiglitazone, saxagliptin, and alogliptin appear to be relatively safe. It is disappointing, however, that neither intensive glycemic control nor the use of specific diabetes medications is associated with any suggestion of cardiovascular benefit. Thus the evidence does not support the use of glycated hemoglobin as a valid surrogate for assessing either the cardiovascular risks or the cardiovascular benefits of diabetes therapy.

Patients with type 2 diabetes and their physicians currently have numerous treatment options, and additional drugs are in development. Perhaps the recent experience with rosiglitazone will allow the FDA to become more targeted in its adjudication of the cardiovascular safety of new diabetes drugs, focusing the considerable resources needed to rule out a cardiovascular concern only on drugs with clinical or preclinical justification for that expenditure. New therapies targeting glycemic control may have cardiovascular benefit, but this has yet to be shown. The optimal approach to the reduction of cardiovascular risk in diabetes should focus on aggressive management of the standard cardiovascular risk factors rather than on intensive glycemic control.

Source: NEJM

 

r�a>�,� �b� n> At 2.5 years, the rate of repeat revascularization was less frequent in the immediate– and staged–preventive PCI groups combined, as compared with the group receiving no preventive PCI (11% and 33%, respectively), and there was a nonsignificant decrease in the rate of cardiac death (5% and 12%, respectively). These studies were limited by a lack of statistical power and a reliance on repeat revascularization as an outcome, which, as indicated above, may be subject to bias. However, the results of these studies are consistent with those of our study.

 

Current guidelines on the management of STEMI recommend infarct-artery-only PCI in patients with multivessel disease, owing to a lack of evidence with respect to the value of preventive PCI.2-5 This uncertainty has led to variations in practice, with some cardiologists performing immediate preventive PCI in spite of the guidelines, some delaying preventive PCI until recovery from the acute episode, and others limiting the procedure to patients with recurrent symptoms or evidence of ischemia. The results of this trial help resolve the uncertainty by making clear that preventive PCI is a better strategy than restricting a further intervention to those patients with refractory angina or a subsequent myocardial infarction. However, our findings do not address the question of immediate versus delayed (staged) preventive PCI, which would need to be clarified in a separate trial.

Several questions remain. First, are the benefits of preventive PCI applicable to patients with non-STEMI?21 Such patients tend to be difficult to study because, unlike those with STEMI (in whom the infarct artery is invariably identifiable), there is often uncertainty over which artery is the culprit. Second, do the benefits extend to coronary-artery stenoses of less than 50%? There is uncertainty over the level of stenosis at which the risks of PCI outweigh the benefits. Third, would a physiological measure of blood flow, such as fractional flow reserve,22,23 offer an advantage over angiographic visual assessment in guiding preventive PCI? Further research is needed to answer these questions.

In conclusion, in this randomized trial, we found that in patients undergoing emergency infarct-artery PCI for acute STEMI, preventive PCI of stenoses in noninfarct arteries reduced the risk of subsequent adverse cardiovascular events, as compared with PCI limited to the infarct artery.

 

Source: NEJM

 

 

 

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Cancer Risk From Diabetes Drugs Unproven, Say AACE/ACE.


There is insufficient evidence linking glucose-lowering medications with an increased risk for cancer, and clinicians can continue to “confidently” prescribe all such Food and Drug Administration (FDA)–approved agents for the management of hyperglycemia, the American Association of Clinical Endocrinologists (AACE) and the American College of Endocrinology (ACE) say in a joint consensus statement released yesterday.

“For most people with diabetes, the benefits of treatment should take precedence over concerns for potential low-grade cancer risk until more definitive evidence becomes available,” according to the AACE/ACE task force for diabetes and cancer.

However, the group also recommends that physicians should “exercise caution when choosing medications implicated in the etiology of cancer for patients with the specific organ-related risk.”

Recent concern has emerged regarding links between diabetes drugs and cancer. In particular, debate has surrounded both a possible link between incretin drugs and pancreatic cancer and between basal insulin glargine (Lantus, Sanofi) and cancer.

But, the AACE/ACA task force explains, evidence suggests that both diabetes itself and obesity may increase the risk for certain cancers, and thus far there are no large-scale randomized studies to definitively link any medication with an increased cancer risk.

The 19-page document reviews the current evidence related to cancer and obesity, endogenous insulin, and diabetes itself, as well as to the various antihypertensive medications.

The authors note that the time lag between exposure to any carcinogen and cancer in humans can be as long as 20 to 50 years. “This is an essential point to consider when weighing the totality of evidence linking disease-state relationships with cancer or the role that pharmacotherapy may play in cancer development.”

Cancer screening and counseling on lifestyle changes should be a part of regular preventive care in people with obesity and/or diabetes, the group advises. Conversely, people who develop “typical” obesity-related cancers, especially at a younger age, should be screened for metabolic abnormalities.

When a physician prescribes antihyperglycemic medications, “a comprehensive risk/benefit analysis must be performed to include assessment of baseline personal and familial risk of malignancies in specific organ systems.”

And in general, “the current totality of evidence should not change clinical practice, though clinicians should be alert to the potential risk and should monitor patients more closely.”

On the flip side, there has also been emerging evidence that metformin and possibly the thiazolidinediones (TZDs) could be associated with a lower risk for cancer, the task force says. “Nonetheless, it is premature to prescribe metformin and TZDs solely for these as-yet-unproven indications.”

Source: medscape.com

Diabetes treatments and cancer risk: the importance of considering aspects of drug exposure.


Summary

Investigations of the association between diabetes, diabetes treatments, and cancer risk have raised several epidemiological challenges. In particular, a patient’s exposure to glucose-lowering drugs needs to be represented accurately to allow unbiased assessment of the link between the treatments and cancer risk. Many studies have used a simple binary contrast (exposure to a specific drug vs no exposure), which has potentially serious drawbacks. In addition, methods used to determine the duration and cumulative dose of drug exposure differ widely between studies. In this Review, we discuss representation of drug exposure in pharmacoepidemiological investigations of the connection between diabetes drugs and cancer risk. We identify principles that might improve future research (particularly in observational studies), and consider issues related to reverse causation and detection bias.

Introduction

Diabetes mellitus is a major public health challenge in many countries. WHO estimates that 350 million people have diabetes worldwide.1 Investigators of epidemiological studies have identified associations between diabetes and an increased risk of some cancers. Evidence for these associations has been summarised in reviews and meta-analyses of cancer of the breast,2endometrium,3 prostate,45 liver,67 pancreas,89 bladder,10 colon and rectum,11—14 and kidney,15 and of non-Hodgkin lymphoma.16 In all these types of cancer, except cancer of the prostate, diabetes is linked to increased risk. Many possible explanations for these associations have been reviewed.17—20

Three mechanisms exist that might (alone or in combination) explain the link between diabetes and cancer: risk factors common to both disorders (eg, obesity or physical inactivity), direct causal effects of metabolic derangements in diabetes on cancer development, and the effect of diabetes treatments. We acknowledge the importance of lifestyle interventions (smoking cessation, increased physical activity, a healthy diet, and maintaining a healthy weight) in reducing cancer risk; however, this Review is limited to methodological challenges in studying the effects of diabetes drugs.

Conclusions

Investigation of the association between treatment of diabetes and risk of cancer is complex, and substantial scope exists for false-positive and false-negative conclusions to be made about causality. Accurate representation of exposure is one key dimension of high-quality studies in this specialty, and is arguably as important as other features of study design such as avoidance of other forms of bias, adequate sample size, appropriate adjustment for confounders, and the use of validated data sources. The use of validated data sources is arguably of particular importance in this article; we discussed how drug exposure can be represented in analysis, but the source data used to construct that representation should be of the highest possible quality. One example of a data source that has been subjected to extensive validation is the General Practice Research Database.67 This resource has an international reputation for the study of drug safety,67 and has been used in several studies of diabetes drugs and cancer risk.52—54 Two reports6869 have described the validity of cancer outcomes recorded in the General Practice Research Database and contributors suggest that validation could improve data quality.

Our examination of a small and opportunistic sample of studies about diabetes treatments and cancer risk suggests that a wide range of approaches have been used to represent exposure to glucose-lowering drugs. Although we recognise that all investigations are inevitably subject to resource constraints, we suggest that future studies observe three principles for the representation of exposure. First, investigators should carefully consider the restricted validity and value of simple binary representations (ever-or-never). Where such representations are unavoidable, investigators should apply of some form of sensitivity analysis (as Monami and colleagues32 used), if feasible. Second, construction of measures that represent total exposure (ie, dose—duration products), analogous to the pack year used in tobacco studies, offers potential benefits and could be explored. Third, the concept of continuity of exposure (ie, continuous versus interrupted treatment) has received relatively little attention. Representation of this concept in an analysis will be challenging, both to obtain the necessary detailed prescription data and in developing appropriate analysis techniques (eg, multistate models). However, continuity of treatment is, arguably, a meaningful component of the total exposure experience, and representation should be considered if possible. Finally, adherence to drug regimens is not likely to be complete, is difficult to assess, and could result in differential misclassification bias and underestimation of the real effect of a drug.

Source: Lancet

 

Has pancreatic damage from glucagon suppressing diabetes drugs been underplayed?.


Incretin mimetics have been called “the darlings of diabetes treatment” and they may soon also be licensed for treating obesity. But a BMJ investigation has found growing safety concerns linked to the drugs’ mechanism of action. Deborah Cohen asks why patients and doctors have not been told.

They’ve been touted as the “new darlings of diabetes treatment”—the biggest breakthrough since the discovery of insulin nearly a hundred years before. The so called incretin therapies—glucagon-like peptide-1 (GLP-1) agonists and dipeptidylpeptidase-4 (DPP-4) inhibitors—looked as if they might change the face of type 2 diabetes. Their dual action of switching on insulin and suppressing glucagon to help control blood glucose was the ultimate in diabetes care.

The promise of a Nobel prize for the investigators loomed large. Scientists had discovered a treatment that could potentially modify disease progression. Studies in experimental animals showed that GLP-1 caused a proliferation in new insulin producing β cells. The hope was that these new cells might be able to replace those that died off in the course of human diabetes.

Nor did the promise end there. GLP-1 acts on the brain to makes people feel less hungry and the more powerful drugs aid weight loss—rather than weight gain like many antidiabetic drugs before them.

It’s an effect companies are seeking to market in its own right. Spurred on by the US Food and Drug Administration’s willingness to license new obesity treatment, Novo Nordisk’s chief science officer Mads Krogsgaard Thomsen said last year that the “political establishment in the US now knows that behaviour change alone is not enough.”1

His company’s drug, liraglutide, is in the process of late stage clinical tests, which Thomsen says show promising results.

But an investigation by the BMJ suggests Thomsen’s confidence might be optimistic. Concerns held by some specialists about the potential side effects of GLP-1 drugs have emerged into the mainstream after both the FDA and the European Medicines Agency announced in March that they would launch a review into whether the drugs may cause or contribute to the development of pancreatic cancer.

As yet neither agency has reached any conclusions, but they are meeting to discuss the matter later this month. And, as this investigation has found, for the regulators it is not a new concern. Over the years, drug assessors have become increasingly concerned that the incretin drugs have the potential for unwanted proliferative effects.

Expert concerns

Concerns long held by some experts about the potential side effects of incretin mimetics have gathered momentum with three publications this year. An independent analysis of health insurance data published in February found that people taking exenatide and sitagliptin were at twice the risk of hospital admission for acute pancreatitis compared with people taking other antidiabetic drugs2—the absolute risk 0.6%. And in April an analysis of data from the US Food and Drug Administration’s adverse event reporting system showed an increase in reports for pancreatitis and pancreatic cancer in people taking incretin mimetics compared with those taking other antidiabetic drugs.3

The FDA and EMA have both confirmed to the BMJ that their own analyses also show increased reporting or signals of pancreatic cancer with incretin mimetics. But they emphasise that this does not mean the relation is causal.

Both agencies announced in March that they will review data from a study just published showing pre-cancerous and dysplastic changes to the pancreas in organ donors exposed to incretin mimetics.4

The evidence is fiercely contested, with manufacturers stoutly defending the safety of their products. Merck, for example, told the BMJ that independent observational studies and a meta-analysis of clinical trials involving 33 881 patients found no association between DPP-4 inhibitors and pancreatic cancer. Bristol-Myers Squibb says that “post-marketing data does not confirm a causal relationship between saxagliptin or exenatide and pancreatitis and/or pancreatic cancer” (see bmj.com for full questions and answers with manufacturers).

But a “Dear Doctor” letter from Bristol-Myers Squibb and AstraZeneca on the UK Medicine and Healthcare Products Regulatory Agency’s website says: “A review of reports of pancreatitis from post-marketing experience revealed that signs of pancreatitis occurred after the start of saxaglitpin treatment and resolved after discontinuation, which is suggestive of a causal relationship. Moreover, pancreatitis has been recognized as an adverse event for other DPP-4 inhibitors.”5 A spokeswoman for Boehringer Ingelheim told the BMJ: “Pancreatitis has been reported in clinical trials and spontaneous post marketing sources. Guidelines for the use of linagliptin in patients with suspected pancreatitis are included in the prescribing information of the treatment.”

The increasingly fractious debate among scientists and doctors was played out last month in the specialty journal Diabetes Care.

Experienced GLP-1 investigator, Professor Michael Nauck, head of the Diabeteszentrum in Bad Lauterberg, Germany, and a consultant to many of the manufacturers, argued that the published evidence against the drugs is weak. “The potential harms and risks typically refer to rare events and are discussed in a controversial manner,” he wrote.6 But a team of four academics from the US and UK (one an expert witness in litigation against one of the manufacturers) suggested that neither the safety nor the effectiveness of the class can be assumed. “The story is familiar. A new class of antidiabetic agents is rushed to market and widely promoted in the absence of any evidence of long-term beneficial outcomes. Evidence of harm accumulates, but is vigorously discounted,” they wrote in their response. 7

In the course of this investigation, the BMJ has reviewed thousands of pages of regulatory documents obtained under freedom of information and found unpublished data pointing to unwanted proliferative or inflammatory pancreatic effects.

The BMJ has also found that, despite published reports that indicated safety concerns, companies have not done critical safety studies; nor have regulators requested them. And access to raw data that would have helped resolve doubts about the safety of these drugs has been denied.

On their own, the individual pieces of unpublished evidence may seem inconclusive — increases in size and abnormal changes in animal pancreases, raised pancreatic enzyme concentrations in humans, reports of thyroid neoplasms, and pancreatitis in early clinical trials.

But when considered alongside other emerging and long standing evidence—such as concerns about the effect of GLP-1agonists on α cells first published in 19998; the presence of the GLP-1 receptor on cells other than the target pancreatic β cell; and increasing signals from regulatory databases2 9—a more coherent and worrying picture emerges, posing serious questions about the safety of this class of drug.

What’s going on in the pancreas?

In a world where the prevalence of type 2 diabetes is increasing rapidly, finding new targets for therapy is a high priority for drug companies. The discovery by scientists in the 1970s and the then publication in 1993 by Michael Nauck of the double action of GLP-1 (glucagon-like peptide-1) provided just such a target.

GLP-1 is a hormone-like peptide released by the intestine in response to a meal; its functions include regulating insulin and blood glucose and slowing gastric emptying. In his study, Nauck found that GLP-1 both increased the insulin made in the pancreas and, by inhibiting the secretion of glucagon, reduced the glucose released by the liver. Excessive glucose release by the liver underpins the high circulating glucose that defines type 2 diabetes. Following secretion, GLP-1 is quickly inactivated by an enzyme, dipeptidyl peptidase-4 (DPP-4). The GLP-1 drugs are either analogues that are not inactivated by DPP-4, taken by injection (exenatide, liraglutide) or oral drugs that inhibit DPP-4 (sitagliptin, saxagliptin, and linagliptin).

The saliva of the desert dwelling Gila monster was the source for the first GLP-1 analogue on the market, exenatide. A heavy slow moving lizard, it eats once or twice a year, and uses the secretion of its salivary hormone exendin-4—which displays similar properties to GLP-1—to induce proliferation of its pancreas and gut to assimilate a meal. Some say this should have provided a valuable clue to the unwanted effects of raised circulating levels of a hormone that usually lasts for only minutes before it is broken down.

But now that most of the other treatments for type 2 diabetes are off patent, these are valuable drugs. Merck’s market leading drug sitagliptin generated about $4.1bn (£2.6bn; €3bn) in sales in 2012 with liraglutide’s 2012 sales of $1.7bn coming in behind. The profit margins mean there is much at stake for the companies and the organisations and doctors who depend on their support.

However, serious doubts about the wisdom of basing treatments on GLP-1 agonists have existed since the beginning. And the companies and regulators have, on reflection, had in their hands ample warning signs—and chance to resolve some of the emerging controversies.

In 2005, the New England Journal of Medicine published a study that showed pancreatic changes in patients who had a type of gastric bypass surgery called Roux-en-Y. The authors noted hypertrophy and hyperplasia of the islet cells, also affecting the cells in the pancreatic ducts. They thought this might be due to raised levels of the hormone GLP-1, which were known to occur after this type of procedure.21 (A later study on this type of surgery also showed a “pronounced” increase in α cell mass22).

Senior executives from Amylin and Lilly wrote to the New England Journal to distance their drug from the paper and to stress the lack of evidence of a pathological effect on the islets in animal studies. “A study of nine months’ duration in healthy cynomolgus monkeys at doses of more than 400 times those used in humans showed minimal-to-mild islet hypercellularity with no increase in islet size (data on file, Amylin Pharmaceuticals),” they said.

The suppression of glucagon by incretin mimetics was highlighted by companies in their drug licensing applications and was noted by regulators. Billions of dollars of sales later, after concerns have been raised about the safety of glucagon suppression and its effect on glucagon producing α cells, the extent to which they do this is being contested.

Butler and colleagues’ finding of α cell hyperplasia in humans taking GLP1 based drugs4 was not the first. In 1999 GLP-1 researcher Joel Habener and a team at Harvard found that exendin-4 (exenatide) induced an increase in α cells in rats.8

But evidence of α cell hyperplasia has come from multiple models and sources—including the companies themselves. Whether this is applicable to GLP-1 based treatments is subject to fierce debate.

Only last October, Professor Dan Drucker, a long standing consultant to many of the companies, gave a keynote lecture at European Association for the Study of Diabetes conference. “The therapeutic window for reduction of glucagon action to manifest beneficial effects for glucose control while avoiding enhancement of hepatic lipid storage, dyslipidemia, hepatocyte injury, and α-cell proliferation in diabetic subjects is unclear,” the official conference journal reported.23

Others in industry have previously highlighted the important role of glucagon suppression in the control of diabetes. In 2005 at a session entitled “GLP-1s: the new darlings of diabetes treatment” Jens Holst, scientific director of the Novo Nordisk Foundation for Metabolic Research at Copenhagen University and a long standing consultant to the company, told the American Diabetes Association annual conference that GLP-1 agonists were a powerful inhibitor of glucagon secretion, adding that he thought this would be “a very important action to diabetes patients.”

A spokesperson for Novo Nordisk acknowledged an effect on α cells but only from full not partial glucagon suppression. She told the BMJ: “Complete removal or blocking of the glucagon receptor, or important signalling components, have caused α cell hyperplasia. This is separate from the relatively modest lowering of glucagon secretion induced by GLP-1.”

The BMJ asked Drucker about this. In response he sent a copy of an article he had written in Cell Metabolism, but this did not describe α cell effects.24 Yet the BMJhas found that the companies were aware of the unwanted effects of the full and partial suppression of glucagon before the incretin mimetics came onto the market.

At the turn of the century, Holst, working with scientists from Novo Nordisk, reported that glucagon suppression in mice resulted in massive enlargement of the pancreas and the proliferation of α cells (α cell hyperplasia).25 They concluded that α cells appear not just in the islets but in the pancreatic ductal epithelium—something that Butler and colleagues found. Importantly, this effect did not require complete blocking of glucagon receptors or the stopping of glucagon production. Even a partial reduction in the hormone signalling resulted in α cell hyperplasia, as shown by Eli Lilly in 2004.26 The Lilly team acknowledged that they hadn’t seen any neoplasia; the studies up until that point had been short—only four months long. They suggested that both glucagon and its receptor must be functional in order to maintain a feedback loop that restrains α cell growth “but the exact nature of this feedback loop is unclear.”26

Over the years, evidence of the effects of modifying glucagon signalling has mounted. In 2009 Run Yu, codirector of the carcinoid and neuroendocrine tumour programme at Cedars Sinai Hospital in Los Angeles, published a report in patients with a rare condition causing deficiencies in glucagon signalling.27 He found α cell hyperplasia and neuroendocrine tumours.

“In type 2 diabetes glucagon plays a role but there is a price to pay with reducing it,” he told the BMJ.

Yu said that he had shared his view with certain companies after the study came out. Because of agreements with the companies, he was unable to say which they were.

He then did a study in mice with decreased glucagon signalling that was far longer than any conducted by the companies. He found that neuroendocrine tumours invariably developed after formation of α cell hyperplasia and eventually led to death. Yu concluded that glucagon suppression was not a safe way to treat diabetes.28But whether this applies to GLP-1based therapies is still uncertain.

In the course of this investigation, the BMJ has looked at thousands of pages of regulatory documents from both the FDA and the EMA. There seems to be little discussion about the potential adverse effects of interfering with glucagon signalling on the α cell, even though the manufacturers spelt out —and the regulators noted—that glucagon suppression was one of the effects of the drugs. Michael Elashoff, a former FDA reviewer who has analysed the safety of the drugs, believes the regulators should have been more cautious in approving them.

“If some of the side effects can be anticipated in advance, then it seems incumbent upon the FDA to really force the companies to do real significant investigation of these potential side effects before the drug goes on the market and not leave it to experiment with actual patients taking the drug,” he said.

The FDA maintains that: “Long-term studies of incretin mimetics in rodents, dogs, and monkeys failed to demonstrate adverse pancreatic pathology or other toxicology reflective of a glucagon deficit that could be interpreted as a clear risk to human subjects.”

The BMJ asked the five companies who market incretin mimetics if they have ever studied the effects of glucagon suppression on the proliferation of α cells. Only Novo Nordisk responded to the question. It stressed that it had never seen α cell hyperplasia in any of its studies.29 30 31 “Alpha-cell hyperplasia is not mediated by the GLP-1 receptor,” a spokeswoman said. Behind the scenes, concerns also started to emerge about the potential inflammatory effects on the pancreas. Effects on pancreatic enzymes: Internal industry documents show that in 2005, one industry key opinion leader reported “extremely high” lipase levels in a patient taking exenatide. He was concerned that the company had missed signs of potential inflammation in its clinical trials.

Dennis Kim, then executive director at Amylin, wrote in an email that the doctor’s report was a “bit concerning” and confirmed that pancreatic amylase and lipase were not measured systematically in the company’s clinical trials.

The BMJ has found that companies have measured these enzymes for “safety issues,” but in many cases the data have not been reported in the published studies.

For example, in one Lilly funded trial comparing weekly exenatide with sitagliptin and two other diabetes treatments—insulin and pioglitazone—enzyme levels increased in a higher percentage of people taking incretin mimetics after 26 weeks of treatment.

Regulatory documents show the mean (SD) lipase concentration in the exenatide group increased from 42.0 (23.77) U/L on day 1 to 60.8 (38.39) U/L at week 26. Sitagliptin also increased lipase from 40.3 (21.3) U/L to 48.7 (30.7) U/L. The levels in the pioglitazone control dropped. However, when the trial was published in theLancet, these data did not make the final cut.32 The company did not say why when the BMJ put it to them. Neither did lead author, Richard Bergenstahl, answer theBMJ’s queries.

Earlier this year, the Lancet published another study funded by Eli Lilly and Amylin in which enzyme levels were measured but not reported.33 “Routinely measured concentrations of pancreatic lipase and total amylase varied in both groups and were not predictive of gastrointestinal symptoms,” the paper said.

The FDA says that the clinical value of routine amylase and lipase monitoring in asymptomatic patients is not clear. But pancreatologists, have told the BMJ that reporting enzyme levels is important because they may reflect a subclinical effect of the drug.

“Many large phase III trials report findings of significant biochemical abnormalities, even though the clinical significance may be uncertain at the time, and in this case where the drug is known to exert effects on the pancreas, I would find such information of value,” Thor Halfdanarson, a pancreatic surgeon, at the Mayo Clinic in Arizona said.

Indeed, writing in support of incretin mimetics in Diabetes Care last month, Michael Nauck said that the effect on pancreatic enzymes may be important.6 “Effects of GLP-1 receptor stimulation on pancreatic enzyme synthesis, potential leakage into the circulation rather than direct secretion into pancreatic digestive juice, and a potential induction if a chronic inflammatory response need to be studied,” he said.

 

Source: BMJ

 

 

Thiazolidinediones and Bladder Cancer Revisited.


Prolonged TZD use might cause bladder cancer.

In several studies, the diabetes drug pioglitazone (Actos) has been associated with risk for bladder cancer (JW Gen Med Jun 21 2012). In this retrospective study, researchers used a U.K. database to compare the incidence of bladder cancer in 18,000 users of thiazolidinedione (TZD) drugs (i.e., pioglitazone and rosiglitazone [Avandia]) and 41,000 users of sulfonylureas. Although median follow-up was about 3 years, follow-up exceeded 5 years in 25% of patients.

Overall, 197 bladder cancers were diagnosed (about 1 case per 300 patients). After adjustment for potential confounders, risk for bladder cancer was significantly higher after 5 years of TZD use (hazard ratio, 3.42 for 5-year users compared with risk in <1-year users). Moreover, 5 years of TZD use was associated with higher incidence of bladder cancer than 5 years of sulfonylurea use (HR, 2.53); with shorter durations of use, incidence was similar in the TZD and sulfonylurea groups. Pioglitazone and rosiglitazone conferred similar risks.

Comment: The evidence for an association between TZDs and bladder cancer — albeit mostly from observational studies — is mounting. The mechanisms are unclear: In basic science studies, agonists of PPAR– (the TZD receptor) affect cell differentiation and proliferation in various ways. In any case, we have little reason to prescribe TZDs, which are not essential for managing diabetes and which are associated with other adverse effects.

Source:Journal Watch General Medicine