A biotech backed by Bill Gates is developing therapies that could treat everything from skin diseases to cancer

A Chicago-based biotech that's backed by Bill Gates wants to build treatments that can silence genes to treat diseases like cancer.

In September, Exicure, led by 36-year-old David Giljohann, raised $20 million from investors including Gates, AbbVie Ventures, Groupon cofounder Eric Lefkofsky, and retired Microsoft executive Craig Mundie, among others. In total, Exicure has raised $62 million. Giljohann is one of Business Insider's top leaders under 40 in biotech and pharma.

The company's building drugs built out of RNA, or ribonucleic acid, that can silence mutated genes that make faulty proteins that cause diseases like psoriasis or cancer. RNA is the instructions cells need to make proteins. The ideas is if you can silence those mutated genes, you could stop the faulty proteins from being created.

The problem these treatments have faced, is that it's hard to get these treatments into the cells you want to target. But Exicure thinks it has a fix.

While working on his Ph.D. at Northwestern University, Giljohann built spherical structures that look like "Koosh balls" made of nanoparticles and DNA or RNA. The aim is to use the structures to deliver the DNA or RNA directly into cells virtually "anywhere your inside touches your outside," so your skin, lungs, eyes, and gastrointestinal track, Giljohann said.

So, for example, for psoriasis, a skin condition, the drug is applied on the skin. The hope is that by treating diseases locally, they might work better than a drug that's swallowed or injected and spread around the entire body.

"We're leveraging the fact that we can get into so many cells and tissues to go after local delivery," Giljohann said.

Exicure isn't the only company working to develop RNA-based treatments. The field has had some challenges historically, but in September, Alnylam Pharmaceuticals announced it had received positive results for its trial of an RNA-based drug to treat a condition called hereditary ATTR amyloidosis with polyneuropathy, in which amyloid proteins build up in the body. The company now plans to file for FDA approval.

So far, Exicure has three drugs in early clinical trials, two to treat psoriasis, and one that's being looked at to treat solid tumors.