Implications of the Phase 4 Trial of Metreleptin in Patients With General Lipodystrophy

The recently completed phase 4 analysis of the impact of drug-neutralizing antibodies created during metreleptin treatment on patient outcomes has provided a window into the efficacy of metreleptin and its clinical implications for general lipodystrophy (GL).1

These data were presented at the Endocrine Society (ENDO) Annual Meeting 2026 in Chicago, Illinois, by Elif Oral, MD, a professor in the Division of Metabolism, Endocrinology, and Diabetes at the University of Michigan, after the conclusion of the aforementioned phase 4 study, which was mandated by the US Food and Drug Administration (FDA) following metreleptin’s approval in 2014.1

“I think our new assay that was developed appears to be super sensitive and maybe detecting a signal that may not be clinically significant,” Oral told HCPLive in an exclusive interview. “Where do you draw the line of clinical significance? It’s only through studies like these, which are done longitudinally and followed over long periods of time, that we could potentially come up with the cutoff for clinical significance.”

Metreleptin is a recombinant analog of human leptin, differing from naturally produced leptin by an additional methionine. Administered by either a once or twice daily subcutaneous injection, metreleptin received approval for general lipodystrophy as an adjunct to diet in 2014 after demonstrating improvements to insulin resistance, diabetes, and hypertriglyceridemia.2

The current study implemented 2 separate assays to analyze anti-drug-antibody-positive patients. The first, an in vitro cell-based assay, was an established system measuring cell proliferation after exposure to metreleptin. The second, a more sensitive electro-chemiluminescent leptin receptor blocking (RB) assay, was largely developed for the purpose of the study, and ultimately provided what the team determined to be more accurate and informative data.1

The trial screened 11 patients, of whom 6 had congenital GL and 5 had acquired GL, and enrolled and assessed 10. Median duration of metreleptin exposure was 35.1 months (range, 4 days to 37.5 months; minimum-maximum dose, 1.25-7.5 mg/day). These patients were monitored for ≤36 months – Oral and colleagues took and tested serum samples for antibodies to both metreleptin and natural leptin via an immunoassay, conducted at months 1, 2, 4, 6, 9, 12, 18, 24, 30, and 36.1

Median time to peak titer for anti-drug antibodies was 4.2 months, compared to 6.6 months for RB neutralizing activity. Oral and colleagues saw a decline in anti-drug antibody response after peak titer in over half of patients, resolving in 1 patient. RB neutralizing activity also decreased after peak titer in ≥70% of antibody-positive patients, resolving in 5. The CB assay only detected neutralizing activity in 1 patient, who later tested negative at month 30.1

Ultimately, the team concluded that testing based on neutralizing antibody activity had confirmed that the RB assay was significantly more sensitive. Additionally, they failed to find a correlation between the neutralizing activity of these antibodies and treatment outcomes, indicating no need for further safety signals outside of what is currently known.1

Oral also addressed the lack of a consistent association between the neutralizing antibodies and loss of metabolic response. She noted that, while the current trial was unable to fully answer whether this lack of association will become a clinical issue, further research over longer periods of time will likely be capable of providing further information.

“Some of these answers, I think, will emerge over a longer period of time, and with the collation of more data now that this new assay is developed,” Oral said. “We’re actually compiling data that stands over a course of a decade and a half of patient trajectories, so I’m hoping that we’ll be able to give better answers to these questions soon.”

Editors’ Note: Oral reports disclosures with Ionis, Akcea, Regeneron, Third Rock Ventures, Amryt Pharmaceuticals, Novo Nordisk, and others.

References

1. Oral E, Christofides E, Wyne K, et al. A 36-Month, Multicenter, Open Label Phase 4 Study to Evaluate the immunogenicity of Daily Metreleptin Treatment in Patients with Generalized Lipodystrophy. Abstract presented at the Endocrine Society (ENDO) Annual Meeting 2026, Chicago, IL. June 13-15, 2026.

2. Chan JL, Koda J, Heilig JS, et al. Immunogenicity associated with metreleptin treatment in patients with obesity or lipodystrophy. Clin Endocrinol (Oxf). 2016;85(1):137-149. doi:10.1111/cen.12980