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Startup IDRx raises $122m to focus on combination drug treatments

It’s licensing small-molecule medicines from Merck KGaA and Blueprint Medicines.

Biotech entrepreneur and investor Alexis Borisy, and Ben Auspitz, chief executive of IDRxAlly Rzesa

For years, physicians have prescribed patients combination therapies to better treat certain diseases.

But it usually happens after two drugs are approved separately and doctors discover the medicines work well together. Now a company founded by some big names in biotech wants to create cancer therapies that are meant to do that from the start.

IDRx, which stands for “intelligently designed combination therapies,” emerged from stealth mode Tuesday with $122 million in funding, led by Andreessen Horowitz and Casdin Capital.

The company is at the clinical stage of drug development, after licensing small-molecule medicines from Germany-based Merck KGaA and Cambridge biotech Blueprint Medicines that would be used to treat gastrointestinal stromal tumors, a type of cancer involving the digestive system.


Though IDRx is new, the idea behind it — combining drugs to fight diseases — is more than 20 years old. It’s what led serial biotech entrepreneur and investor Alexis Borisy to launch Cambridge-based CombinatoRx in 2000.

“We said let’s combine every possible drug we could get our hands on and just see what we could learn,’” Borisy said. “[It was] really sort of a brute force approach.”

The company eventually fell apart, but Borisy always believed in the premise. So when scientists from Merck approached him a little over a year ago with what they thought could be a best-in-class molecule for a type of cancer, he had an idea.

The molecule might work fine on its own, Borisy figured, but he wondered whether it might be more effective if developed in combination with another drug. He was encouraged by the fact that — unlike the CombinatoRx days — scientists now have more precise drug engineering capabilities and a deeper understanding of what causes some cancers.

“We said, ‘Well, can you do it rationally this time?’” Borisy said.

Ben Auspitz, who worked at CombinatoRx and is chief executive of IDRx, said the company was also inspired by successful drug combination regimens, such as those developed by Boston biotech Vertex to tackle cystic fibrosis. He hopes to apply to same concept to cancer.


“The nature of this one tumor ... is such that we really think we know the biology,” Auspitz said.

Borisy brought the idea to Blueprint, where he serves on the board of directors. He thought the firm likely had a molecule to pair with the one from Merck. Blueprint found the molecule, but it didn’t want to take on a new combination drug program and was willing to license it out instead.

Merck’s drug is in early stage human trials, and Blueprint’s is expected to enter human trials next year.

IDRx employs less than 10 people. Its corporate address is in Plymouth, but the company’s employees work remotely in the Boston area.

Anissa Gardizy can be reached at anissa.gardizy@globe.com. Follow her on Twitter @anissagardizy8 and on Instagram @anissagardizy.journalism.