This Chemical Compound Could Melt Away Cataracts

Eye drops made from “compound 29” have been shown to reduce cataracts in mice. Researchers hope the same will hold true for humans.

Cataract of the human eye (© ScienceVU, Inc/Visuals Unlimited/Corbis)
smithsonian.com

Imagine looking through a fogged-up car window. You can see shapes and movement on the other side, but everything is blurry, the colors muted. Now imagine if that’s what the world looked like every time you opened your eyes. That’s what life is like for the millions of people living with cataracts, the leading cause of blindness globally.

While cataracts can be easily removed with surgery, this is an invasive and expensive option. In the developing world, patients may not have access to surgery at all. So a recently announced non-surgical treatment for the condition—a chemical compound that could “melt” cataracts away when applied as an eye drop—has the potential to make a big impact in the medical community.

The compound was discovered by a team of scientists from several U.S. universities. Their findings were published this month in the journal Science.

The lens of the human eye is made mostly of water and proteins. While most proteins in the human body are renewed on a regular basis, this is not true of lens proteins.

“Your lens proteins are the same proteins that you’re born with,” says Jason Gestwicki, a professor of pharmaceutical chemistry at University of California, San Francisco. “They’re as old as you are.”

In a healthy lens, the proteins are neatly folded. But age, genetics and environmental factors can cause the proteins to form clumps, called amyloids. These clumps interfere with vision, causing the characteristic clouding associated with cataracts. The amyloids can first appear in a person’s 40s or 50s, but may not cause significant vision impairment until their 60s or later.

Gestwicki and his team members wondered if it would be possible to find a chemical compound that could affect amyloids. The possibilities were many: they started with nearly 2,500 compounds, eventually winnowing the field down to 12 compounds in the chemical class known as sterols. One sterol, called lanosterol, has previously been shown to affect cataracts, but only when injected directly into the eye. The team wanted something that could be used in eye drop form. Another of the 12 sterols stood out. Called “compound 29” by the team, it was shown in petri dish testing to dissolve amyloid clumps with a high degree of efficiency.

The next step was testing compound 29 on mice with cataracts. These mice were treated three times a week for six weeks, using drops of compound 29 in their right eye and an inert control in their left eye. At the end of the six week period, researchers examined the mice using a slit-lamp exam, which is how ophthalmologists measure cataracts in humans. The drops seemed to have dissolved many of the amyloids, making the lenses transparent again.

The next step will be human testing. Gestwicki and fellow researcher Leah Makley have founded a company, ViewPoint Therapeutics, which hopes to develop a safe cataract-fighting eye drop. “If everything goes right,” Gestwicki says, they will begin human testing in the next two years or so.

The implications of compound 29 don’t end with cataracts. Amyloids are the signature of a number of age-related diseases, including Alzheimer’s and Parkinson’s. If it’s possible to melt these clumps of protein in the human eye, then in theory a similar approach could work on the brain as well. Gestwicki hopes to look at this possibility in the near future. Compound 29 itself might not be the breakthrough to treating neurological amyloid diseases, he says. But it’s given scientists a better understanding of how such a process could work.

“Compound 29 really showed us the features of such a molecule that we might want,” Gestwicki says. “I think it was a really important milestone.” 

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