In this episode of Diabetes Dialogue: Technology, Therapeutics, & Real-World Perspectives, hosts Diana Isaacs, PharmD, and Natalie Bellini, DNP, speak with John Buse, MD, PhD, of the University of North Carolina School of Medicine, about the treatment phase of the CATALYST trial.

Findings from the phase 4 CATALYST trial suggest that mifepristone (Korlym), a glucocorticoid receptor antagonist, significantly improves glycemic control, reduces body weight, and lowers waist circumference in patients with hypercortisolism and difficult-to-control type 2 diabetes—offering a promising therapeutic option for a population with limited treatment success.

The two-part, multicenter study enrolled 1055 adults with type 2 diabetes and HbA1c >7.5% despite optimized therapy. In part 1, participants underwent dexamethasone suppression testing to identify hypercortisolism, defined by post-test cortisol levels >1.8 µg/dL and dexamethasone >140 ng/dL. Results revealed a 24% prevalence of hypercortisolism in this population (95% CI, 21.4–26.7%).

Part 2 randomized 136 patients with confirmed hypercortisolism in a 2:1 ratio to receive mifepristone or placebo for 24 weeks. The primary endpoint was change in HbA1c. Mifepristone treatment led to a least squares mean HbA1c reduction of 1.3 percentage points compared to placebo (95% CI, –1.81 to –0.83; P < .001).

Secondary endpoints also favored mifepristone: body weight decreased by 5.12 kg (95% CI, –8.20 to –2.03), and waist circumference dropped by 5.1 cm (95% CI, –8.23 to –1.99) relative to placebo.

Despite its efficacy, 49% of mifepristone-treated patients discontinued therapy, compared to 18% on placebo. Adverse events included hypokalemia, fatigue, nausea, vomiting, and elevated blood pressure, consistent with the drug’s known safety profile.

During the episode, which was recorded during the 85th Scientific Sessions of the American Diabetes Association (ADA 2025), Buse provides hosts with a deep dive into the background of the trial, prevalence of hypercortisolism in difficult-to-control type 2 diabetes, and the historic relevance of the CATALYST results. Buse also discusses how the trial offers insight into dosing approaches with mifepristone and advocates for broader cortisol screening in patients with complex type 2 diabetes—suggesting that ADA Standards of Care should reflect these findings.