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Waltham biotech Pretzel Therapeutics launches with $72.5m

The company is developing gene-editing therapies and drugs for diseases caused by broken mitochondria, the energy source for cells.

Researchers in a Pretzel Therapeutics lab in Gothenburg, Sweden. The company was founded by three scientists in Europe but is headquartered in Waltham.Stig Albansson

In the life sciences industry, where company names derived from “biology” or “genetics” are a dime a dozen, it helps to have a brand that stands out. Pretzel Therapeutics is one of this year’s more creative gambits, launching Monday with $72.5 million in series A financing — just in time for Oktoberfest season.

Alas, the Waltham-based startup has nothing to do with the twisted salty snack. The company is developing treatments for diseases caused by broken mitochondria — the main energy source for human cells. Breakdowns in these microscopic power plants are linked to dozens of diseases, including Alzheimer’s, cancer, metabolic conditions, and several rare genetic diseases.


“There’s such a huge untapped potential in drugging the mitochondria,” said chief executive Jay Parrish.

A San Diego biotech company focused on cancer was originally called Pretzel Therapeutics a few years ago but changed its name to Boundless Bio. “We took the name because we think it fits us a lot better,” Parrish said. “A pretzel looks like a mitochondria — if you squint.”

You’d have to squint pretty hard, because mitochondria are oval-shaped, more akin to a bean than a pretzel. But Parrish said it’s the winding layers of membranes inside mitochondria — where molecular machines make fuel for cells — that remind him of a pretzel’s twists. More importantly, “it’s a name you will never forget,” he added.

The startup’s sights are initially set on developing treatments for rare genetic conditions, where malfunctioning mitochondria can cause muscle weakness and cognitive impairment.

These conditions are caused by mutations in mitochondrial DNA — a special genetic code separated from the rest of the genome. Mitochondria often have several copies of their DNA, and mutations in just a portion of those copies can cause disease. Pretzel is developing gene-editing therapies that reduce the portion of mutant DNA in mitochondria.


Based on the results of preclinical studies, the company decided to eschew the popular CRISPR gene editing technology employed by many firms and use instead an older gene editing system based on so-called zinc finger nucleases.

The company is also designing traditional small molecule drugs — usually taken as pills — to turn down or amp up the energy output of the mitochondria, depending on the disease, Parrish said. Additional small molecule drugs can target the cell’s mitochondria quality control system, he said, helping to dispose of old and damaged mitochondria and encourage the cell to make new ones.

Parrish said that the company is moving multiple programs forward in parallel, including rare disease and cancer programs, but he wouldn’t say when Pretzel plans to start clinical trials.

Pretzel was cofounded by three mitochondria scientists in Europe: Dr. Claes Gustafsson at the University of Gothenburg in Sweden, Michal Minczuk at the University of Cambridge in England, and Dr. Nils-Göran Larsson at the Karolinska Institute in Sweden. The startup’s 35 employees are split between its headquarters in Waltham and its labs in Gothenburg, Sweden.

Ryan Cross can be reached at ryan.cross@globe.com. Follow him on Twitter @RLCscienceboss.