MBX joins IPO queue with $100m Nasdaq filing

Further signs that the biotech initial public offering (IPO) market is picking up have come with a filing by MBX Biosciences, seeking around $100 million to take a hypoparathyroidism candidate into phase 3.

The filing comes shortly after Zenas BioPharma and Bicara Therapeutics also threw their hat into the IPO ring, and just a few days after MBX raised $63.5 million in a Series C led by Deep Track Capital that it said would fund operations into 2026. The $100 million figure is likely to be a placeholder amount and could change depending on how well the IPO is received.

Carmel, Indiana-based MBX specialises in the development of what it calls "precision peptides" for endocrine and metabolic diseases, working on peptides that have been modified to improve their properties, for example, by reducing dosing frequency or ensuring consistent drug concentrations in the body.

Lead product MBX 2109 is a prodrug of parathyroid hormone (PTH), which is deficient in hypoparathyroidism, and a would rival to Ascendis Pharma's Yorvipath (palopegteriparatide), another PTH analogue that was cleared by the FDA earlier this month.

Yorvipath's approval alleviated a lot of concern among hypoparathyroidism patients in the US caused by Takeda's plan to stop manufacturing its PTH product Natpara – previously the only FDA-approved option – by the end of this year.

Hypoparathyroidism leads to decreased calcium and elevated phosphorus levels in the blood and causes complications in organs and tissues, such as kidney damage and increased bone mineral density. Low calcium levels can also lead to symptoms like numbness, tingling, muscle twitching, spasms or cramps, abnormal heart rhythm, and seizures.

MBX recently started a phase 2 trial of MBX 2109, with results due in the third quarter of 2025. The drug is designed to be dosed once a week, while Yorvipath needs to be injected every day.

Another potential rival is AstraZeneca's PTH1 receptor agonist eneboparatide, which also needs to be injected daily and is in phase 3. It was recently fast-tracked by the FDA. EnteraBio, meanwhile, has an oral formulation of PTH called EB612 in early-stage clinical testing for hypoparathyroidism.

In its IPO prospectus, MBX said it also intends to use some of the proceeds to advance investigational GLP-1 receptor antagonist MBX 1416 through a phase 1 data readout and into phase 2 for post-bariatric hypoglycaemia, and also bring dual GLP-1/GIP agonist MBX 4291 through preclinical development and into human testing for obesity.

Both drugs are designed to reduce the dosing frequency needed with current GLP-1 and dual GLP-1/GIP drugs – like Novo Nordisk's semaglutide and Eli Lilly's tirzepatide – that need to be injected once a week.

MBX plans to list on the Nasdaq under the symbol MBX. The recent flurry of IPOs adds to the sense that the environment for biotechs seeking to go public after a two-year lull, with a pick-up in the first quarter of 2024 that lost some momentum in the second quarter.