Trial Testing MBX 2109 in Healthy Volunteers Advances to Part 2

Participants will be given one of four doses once weekly in the trial's second part

Vanda Pinto, PhD avatar

by Vanda Pinto, PhD |

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A Phase 1 clinical trial evaluating the safety and pharmacological properties of MBX 2109 — MBX Biosciences’ investigational hormone replacement therapy for people with hypoparathyroidism — in healthy volunteers has moved to its second part.

This portion, which will test multiple MBX 2109 doses, follows the successful completion of the trial’s first, single-dose part. The study (NCT05158335) is taking place at the Labcorp Drug Development Clinical Research Unit in Madison, Wisconsin and Dallas, Texas. The trial is still recruiting participants.

“This is an exciting achievement for MBX as we continue to advance our first clinical program,” Kent Hawryluk, president and CEO of MBX Biosciences, said in a company press release. “We believe MBX 2109 has the potential to address a substantial need in hypoparathyroidism, and this trial brings us a step closer to evaluating it in patients.”

A feature of hypoparathyroidism is abnormally low levels of the parathyroid hormone (PTH), which helps regulate the body’s calcium and phosphorus levels. Damage or removal of the parathyroid glands, which produce PTH, during surgery of the neighboring thyroid gland in the neck is the most common cause of the disease.

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To treat hypoparathyroidism, clinicians often prescribe supplements to normalize calcium and phosphorus. This carries the risk of kidney damage, particularly at high doses, and doesn’t fix the underlying cause, however.

Hormone replacement therapy, wherein a patient receives a lab version of PTH, is another treatment approach.

Natpara (sold by Takeda), the only hormone replacement treatment approved in the U.S. for hypoparathyroidism, was recalled in 2019 because of packaging issues. The company’s proposed cartridge changes were rejected by the U.S. Food and Drug Administration (FDA) earlier this year, delaying a potential relaunch.

Access to the therapy in Europe where it’s sold under the brand name Natpar hasn’t been affected by the U.S. recall.

Delivered through under-the-skin injections, MBX 2109 is a lab-made inactive form of PTH designed to be converted into its active form at a precisely controlled rate once it’s inside the body. Both inactive and active compounds are designed to remain in the body for longer periods, allowing once-weekly dosing.

The FDA granted MBX 2109 orphan drug status for treating hypoparathyroidism this summer. This designation is given to accelerate the development of potential treatments for diseases that affect fewer than 200,000 people in the U.S. Benefits include exemptions from fees and seven years of guaranteed market exclusivity if the treatment wins FDA approval.

The two-part Phase 1 trial is investigating MBX 2109’s safety, tolerability, pharmacokinetics (movement into, through, and out of the body) and pharmacodynamics (effects on the body) in up to 80 healthy men and women, ages 21–60.

In the first part of the study, volunteers received a single under-the-skin injection of either one of six ascending doses of MBX 2109 (50, 150, 240, 360, 440, or 540 micrograms) or a placebo. Results indicated the therapy was safe and well tolerated when compared with a placebo.

In the trial’s second part, participants will be given an under-the-skin injection of either one of four therapy doses (80, 120, 150, or 180 mg) or a placebo once weekly for four weeks.

The study is expected to end in February 2023.