Shift From Surrogate End Point to Outcome Trials: Implications for Cardiovascular Safety Assessment in Development Programs for Antidiabetic Drugs

Estimating the incremental net health benefit of requirements for cardiovascular risk evaluation for diabetes therapies

PURPOSE

To evaluate the advantages and disadvantages of pre-approval requirements for safety data to detect cardiovascular (CV) risk contained in the December 2008 U.S. Food and Drug Administration (FDA) guidance for developing type 2 diabetes drugs compared with the February 2008 FDA draft guidance from the perspective of diabetes population health.

METHODS

We applied the incremental net health benefit (INHB) framework to quantify the benefits and risks of investigational diabetes drugs using a common survival metric (life-years [LYs]). We constructed a decision analytic model for clinical program development consistent with the requirements of each guidance and simulated diabetes drugs, some of which had elevated CV risk. Assuming constant research budgets, we estimate the impact of increased trial size on drugs investigated. We aggregate treatment benefit and CV risks for each approved drug over a 35-year horizon under each guidance.

RESULTS

The quantitative analysis suggests that the December 2008 guidance adversely impacts diabetes population health. INHB was -1.80 million LYs, attributable to delayed access to diabetes therapies (-0 .18 million LYs) and fewer drugs (-1.64 million LYs), but partially offset by reduced CV risk exposure (0.02 million LYs). Results were robust in sensitivity analyses.

CONCLUSION

The health outcomes impact of all potential benefits and risks should be evaluated in a common survival measure, including health gain from avoided adverse events, lost health benefits from delayed or for gone efficacious products, and impact of alternative policy approaches. Quantitative analysis of the December 2008 FDA guidance for diabetes therapies indicates that negative impact on patient health will result.

Rationale, design, and organization of a randomized, controlled Trial Evaluating Cardiovascular Outcomes with Sitagliptin (TECOS) in patients with type 2 diabetes and established cardiovascular disease

Sitagliptin, an oral dipeptidyl peptidase-4 inhibitor, lowers blood glucose when administered as monotherapy or in combination with other antihyperglycemic agents. TECOS will evaluate the effects of adding sitagliptin to usual diabetes care on cardiovascular outcomes and clinical safety. TECOS is a pragmatic, academically run, multinational, randomized, double-blind, placebo-controlled, event-driven trial recruiting approximately 14,000 patients in 38 countries who have type 2 diabetes (T2DM), are at least 50 years old, have cardiovascular disease, and have an hemoglobin A1c value between 6.5% and 8.0%. Eligible participants will be receiving stable mono- or dual therapy with metformin, sulfonylurea, or pioglitazone, or insulin alone or in combination with metformin. Randomization is 1:1 to double-blind sitagliptin or matching placebo, in addition to existing therapy in a usual care setting. Follow-up occurs at 4-month intervals in year 1 and then twice yearly until 1300 confirmed primary end points have occurred. Glycemic equipoise between randomized groups is a desired aim. The primary composite cardiovascular endpoint is time to the first occurrence of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for unstable angina, with cardiovascular events adjudicated by an independent committee blinded to study therapy. TECOS is a pragmatic-design cardiovascular outcome trial assessing the cardiovascular effects of sitagliptin when added to usual T2DM management.

Association of hypoglycemic treatment regimens with cardiovascular outcomes in overweight and obese subjects with type 2 diabetes: a substudy of the SCOUT trial

OBJECTIVE

To assess the association of hypoglycemic treatment regimens with cardiovascular adverse events and mortality in a large population of type 2 diabetic patients at increased cardiovascular risk.

RESEARCH DESIGN AND METHODS

This analysis included 8,192 overweight patients with type 2 diabetes from the Sibutramine Cardiovascular Outcomes (SCOUT) trial randomized to lifestyle intervention with or without sibutramine for up to 6 years. Patients were grouped according to hypoglycemic treatment at baseline. The primary end point was the time from randomization to the first occurrence of a primary outcome event (POE), nonfatal myocardial infarction, nonfatal stroke, resuscitation after cardiac arrest, or cardiovascular death. Multivariable Cox proportional hazards regression models were used to assess the impact of antiglycemic treatment on POE and all-cause mortality.

RESULTS

Treatments for type 2 diabetes were as follows: diet alone (n = 1,394 subjects), metformin monotherapy (n = 1,631), insulin monotherapy (n = 1,116), sulfonylurea monotherapy (n = 1,083), metformin plus sulfonylurea (n = 1,565), and metformin plus insulin (n = 1,000); 905 subjects experienced a POE and 708 died. Metformin monotherapy was associated with lower risk of POE than insulin (hazard ratio [HR], 0.74; 95% CI, 0.57-0.95; P = 0.02). Diet alone also was associated with lower risk of POE (HR, 0.65; 95% CI, 0.48-0.87; P = 0.004). Metformin monotherapy also was associated with lower mortality (HR, 0.73; 95% CI, 0.54-0.99; P < 0.05), whereas no other monotherapies or combination therapies were significantly associated with POE or all-cause mortality compared with insulin as monotherapy.

CONCLUSIONS

In obese patients with type 2 diabetes and high risk of cardiovascular disease, monotherapy with metformin or diet-only treatment was associated with lower risk of cardiovascular events than treatment with insulin.

Antidiabetic agents: past, present and future

Treatment of diabetes mellitus requires, at a certain stage of its course, drug intervention. This article reviews the properties of available antidiabetic medications and highlights potential targets for developing newer and safer drugs. Antidiabetic agents are grouped in the article as parts I, II and III according to the history of development. Part I groups early developed drugs, during the 20th century, including insulin, sulfonylureas, the metiglinides, insulin sensitizers, biguanides and α-glucosidase inhibitors. Part II groups newer drugs developed during the early part of the 21st century, the past decade, including GLP-1 analogs, DPP-VI inhibitors, amylin analogs and SGLT2 inhibitors. Part III groups potential targets for future design of newer antidiabetic agents with less adverse effects than the currently available antidiabetic drugs.