in at-risk individuals.
The 10-7 vote of the FDA’s endocrinologic and metabolic drugs advisory committee on May 27 reflected a difficult decision-making process on the part of many members to weigh the benefits of a potential 2-year delay in the onset of type 1 diabetes against both observed and theoretical risks, as well as what most considered to be insufficient data.
Regardless of their vote, nearly all panel members advised the FDA that the company should be required to conduct at least one additional larger long-term efficacy and safety trial to satisfy what they felt were major gaps in the data. Some advised that use of the drug be restricted to a very narrow group of recipients until efficacy and safety can be better established.
If approved, teplizumab, which interferes with T cell–mediated autoimmune destruction of pancreatic beta cells, would be the first disease-modifying therapy for impeding progression of type 1 diabetes. The proposed indication is for individuals who have two or more type 1 diabetes-associated autoantibodies and subclinical dysglycemia.
That “stage 2” or “at-risk” condition is associated with a nearly 100% lifetime risk of progression to clinical (“stage 3”) type 1 diabetes and a 75% risk of developing the disease within 5 years. As of now, most such individuals are first-degree relatives of people with type 1 diabetes identified through TrialNet.
What’s the evidence to support approval so far?
In 2019, a pivotal phase 2 randomized, placebo-controlled TN-10 trial involving 76 at-risk children and adults ages 8 years and older showed that a single 14-day treatment of daily intravenous infusions of teplizumab in 44 patients resulted in a significant median 2-year delay to onset of clinical type 1 diabetes, compared with 32 who received placebo. Further follow-up data continue to show that fewer patients who received teplizumab have progressed to clinical type 1 diabetes.
While most advisory panelists agreed that the TN-10 study demonstrated efficacy, several also said that the sample size was insufficient and at least one additional randomized trial should be conducted to replicate the findings.
Although the FDA typically requires companies to demonstrate a drug’s effectiveness with at least two separate clinical trials, the agency allows companies to substitute other forms of data for a second randomized clinical trial, such as study results for the drug in a closely related condition, mechanistic data, or knowledge of other drugs from the same class.
In this case, Provention’s submission included as “confirmatory” evidence a meta-analysis of data from five earlier randomized trials (three placebo controlled, two open label) of a total 942 individuals with newly diagnosed type 1 diabetes (“stage 3”) who received either one or two 14-day teplizumab courses (n = 729) or placebo. These showed consistent preservation of C-peptide, a surrogate marker of beta-cell function, along with lower mean insulin use.
Several panel members expressed dissatisfaction with those confirmatory data, noting the patient population was different from those for which the company is currently seeking the indication, and that C-peptide is an inadequate endpoint for demonstrating efficacy.