In the U.S., the FDA grants Orphan Drug designation to drugs or biologics intended to treat, diagnose, or prevent rare diseases or conditions. “Rare” refers to any condition affecting fewer than 200,000 Americans. As a benefit, drug developers also qualify for fee waivers, increased regulatory assistance, tax credits, and 7 years of marketing exclusivity upon approval. According to a late July 2022 news release from biopharmaceutical company MBX Biosciences, Inc., the company’s therapy MBX 2109, for hypoparathyroidism, earned Orphan Drug status.
MBX Biosciences describes MBX 2109 as:
an investigational parathyroid hormone (PTH) peptide prodrug in development as a long-acting hormone replacement therapy for hypoparathyroidism. Under physiological conditions, MBX 2109 (prodrug) is designed to release the active PTH peptide (MBX 2099) at a precisely controlled rate [to reach] our goal [of restoring] PTH physiology, [correcting] the mineral imbalances to alleviate symptoms of the disorder, and [enabling] patients to live healthier lives.
Patients would only need to take one dose of MBX 2109 each week, making it an easier and more efficient treatment option.
Currently, MBX Biosciences is evaluating the safety, pharmacodynamic and pharmacokinetic profiles, and tolerability of MBX 2109 in a Phase 1 study.
What is Hypoparathyroidism?
Hypoparathyroidism is a rare endocrine disorder characterized by low PTH levels. Normally, PTH plays a role in balancing calcium and phosphorus. However, those with hypoparathyroidism have too little PTH. As a result, people have heightened blood phosphorus levels, as well as low blood and bone calcium levels. Surgery, autoimmune diseases, heredity, face or neck cancer treatments, and low blood magnesium may all cause low PTH. Symptoms associated with this condition can (but do not always) include:
- Fatigue and general weakness
- Dry, coarse skin and brittle nails
- Depression and anxiety
- Teeth malformations
- Arrhythmias
- Patchy hair loss
- Muscle aches and cramps which often affect the feet, legs, abdomen, and face
- Twitching or spasms around the mouth and throat
- Tingling or burning in the lips, fingertips, and toes
- Painful menstruation
- Cataracts
- Calcium deposits in the brain
- Tetany
- Paresthesias
- Seizures
- Impaired kidney function
