Eneboparatide, now in Phase 3 trial, placed on fast track by FDA

Therapy designed to mimic parathyroid hormone lacking in patients

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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A medicine bottle, half full of liquid, is labeled clinical trials.

The U.S. Food and Drug Administration (FDA) has given fast track designation to eneboparatide, an experimental treatment for hypoparathyroidism that’s being investigated in a global Phase 3 clinical trial.

This designation is intended to speed the development of therapies with the potential to address major unmet needs for serious conditions. It gives the therapy’s developer, Amolyt Pharma, access to more frequent meetings with the FDA throughout the drug development process, among other advantages.

“We believe FDA’s granting of fast track designation to eneboparatide reflects the agency’s recognition of the significant unmet needs that persist among patients,” Thierry Abribat, PhD, founder and CEO of Amolyt, said in a company press release. “We look forward to maintaining a constructive dialog with the agency as we work to bring new hope to patients suffering from this rare but challenging endocrine disorder as efficiently as possible.”

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A person drinks from a glass in an illustration that magnifies his kidneys.

Impaired kidney function is common in hypoparathyroidism

Hypoparathyroidism treated with calcium and vitamin D supplements

Hypoparathyroidism is caused by abnormally low levels of the parathyroid hormone (PTH), which helps to regulate levels of calcium and phosphorus in the blood. Standard treatment involves supplements of calcium and vitamin D, but this “seldom controls the life altering symptoms and complications of hypoparathyroidism,” according to Mark Sumeray, MD, Amolyt’s chief medical officer.

People with uncontrolled hypoparathyroidism may be “at risk of declining kidney function and diminished bone quality,” Sumeray noted.

Eneboparatide, previously called AZP-3601, is designed to mimic PTH, effectively replacing the hormone missing in hypoparathyroidism patients. The therapy is given via under-the-skin (subcutaneous) injections, and findings from a proof-of-concept Phase 2 trial indicated the treatment could normalize calcium levels.

“In studies to date, eneboparatide has been shown to normalize mean [blood] serum calcium and mean urinary calcium excretion while restoring balanced bone turnover,” Sumeray said. Bone turnover refers to the process of bone resorption followed by replacement with new bone.

Enrolling Phase 3 trial to see if eneboparatide normalizes blood calcium levels

Last year, Amolyt announced plans for a Phase 3 clinical trial of eneboparatide in adults with chronic hypoparathyroidism. The trial, dubbed CALYPSO (NCT05778071), is enrolling about 165 patients, ages 18 through 80, who will be randomly assigned to receive the experimental therapy or a placebo for about six months.

The study’s main goal is to see if eneboparatide can outperform a placebo at normalizing blood calcium levels without the need for supplements. Investigators also will evaluate changes with treatment in patient-reported measures of symptom severity and life quality.

After the trial’s placebo-controlled phase, participants will have the option of continuing or starting treatment with eneboparatide, administered using a prefilled pen, as part of an open-label extension. The study is actively recruiting eligible patients at more than 50 centers across the U.S., Canada, and Europe, with top-line results expected next year.

“Building upon findings from our successful Phase 2 clinical trial, we are working diligently to execute our ongoing Calypso Phase 3 study and look forward to topline data in 2025,” Sumeray said.