Hormone Replacement Therapy MBX 2109 Named FDA Orphan Drug

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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MBX 2109, an experimental hormone replacement therapy that MBX Biosciences is developing for hypoparathyroidism, has been granted orphan drug status by the U.S. Food and Drug Administration (FDA).

The FDA awards this designation to therapies intended to treat rare diseases, defined as those that affect less than 200,000 people in the U.S.

It qualifies MBX, as the therapy’s developer, for certain incentives — including tax credits for qualified clinical testing, exemptions from fees, and seven years of guaranteed marketing exclusivity if the treatment ultimately earns FDA approval.

“This is an exciting achievement for MBX and underscores the significant need to expand treatment options for hypoparathyroidism,” Kent Hawryluk, president and CEO of MBX Biosciences, said in a company press release.

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Hypoparathyroidism is defined by abnormally low levels of the parathyroid hormone, called PTH, which is important for regulating calcium levels in the body. The aim of hormone replacement therapy for hypoparathyroidism is to medically administer a version of PTH to boost its levels in the body.

There is only one FDA-approved hormone replacement treatment for hypoparathyroidism — Natpara, sold by Takeda — but the therapy was recalled in 2019 due to packaging issues. The FDA rejected proposed cartridge changes earlier this year, delaying a potential relaunch.

MBX 2109 contains a peptide prodrug, an inactive protein. Once inside the body, the inactive protein is designed to convert into a specific form of active PTH, intended to have sustained hormone activity, at a precisely controlled rate.

According to MBX’s website, these traits have the potential to enable once-weekly dosing for the therapy.

“We believe MBX 2109, currently in a Phase 1 clinical trial, has the potential to overcome limitations of the current standard of care with fewer administrations necessary due to its long-acting profile,” Hawryluk said, adding, “Our goal is to improve the outcomes and quality of life for patients with this chronic condition.

MBX is sponsoring the Phase 1 trial (NCT05158335), which is testing the safety and pharmacological properties of MBX 2109 in healthy volunteers.

The study consists of two parts: the first is assessing a single dose of MBX 2109, while the second will test repeated doses. MBX 2109 is administered via an under-the-skin (subcutaneous) injection.

Recruitment is ongoing at the single study site at the Labcorp Drug Development Clinical Research Unit, in Madison, Wisconsin. The study is enrolling approximately 80 healthy adults, ages 21 to 60. It is open to men and to women who do not have the capacity to become pregnant.