Sickle cell blood illustration

A link in the chain: untangling sickle cell

A researcher builds on his mentor’s work to create a treatment for sickle cell disease.

By Greg Weatherford

For 30 years, Martin Safo, Ph.D., has worked to find a solution to a complex puzzle: How can chemistry stop human blood cells from twisting and sticking together?

Martin Safo
Martin Safo, Ph.D., has been leading efforts to develop new treatments for sickle cell disease.

The answer is critical for millions of people with sickle cell disease. Their blood cells fold into bizarre shapes and clump together, causing excruciating pain, anemia and often an early death. 

Now Safo, a professor at VCU School of Pharmacy, thinks he may be close to a treatment. “It is quite exciting,” he says.

His team’s innovative compound has proved effective in initial tests and is showing promising results in mouse models. If all goes well, Safo and his fellow researchers at VCU School of Pharmacy plan to start clinical trials in 2022 for the treatment of sickle cell disease. 

“This therapy will improve and save the lives of millions of people,” says Magdalena Morgan, Ph.D., assistant director of VCU Innovation Gateway, which provided a $50,000 commercialization grant in 2018 and is working to bring it to market. “Innovation Gateway is very proud to be a part of this process.”

VZHE-039, which gets its name from the initials of the researchers and the number of attempts it took to find it, draws on work Safo began in 1991. He was hired as a postdoctoral fellow at the School of Pharmacy by Donald Abraham, Ph.D., the founder of the school’s Institute for Structural Biology, Drug Discovery and Development. 

Abraham hired Safo as a protein X-ray crystallographer even though the young man had experience only with a related technique. “He took a chance on me,” Safo says. 

At the time, Abraham was studying the use of vanillin, the simple chemical compound that gives vanilla its distinctive flavor, as a way to treat sickle cell disease. Scientists had noticed that in test tubes vanillin somehow prevented blood cells from forming the characteristic twisted shape that gives the disease its name. 

Safo acknowledges that at the time he had no special interest in finding treatments for sickle cell disease. He had received his Ph.D. from Notre Dame in inorganic chemistry. But he felt inspired by Abraham’s passion and pioneering work to apply the insights of structural biology to medical research. And he had family members who suffered from the disease. 

With Abraham’s encouragement Safo became an expert in the highly technical field, analyzing X-ray images to reveal the three-dimensional structure of proteins that had been crystallized. He started examining hemoglobin. 

Red blood cells in people with the sickle mutation become deformed when their hemoglobin — the part of the blood cell that carries oxygen from the lungs to tissues — drops its oxygen payload. In people with sickle cell, the now-exposed section of hemoglobin with the mutation sticks to other hemoglobin molecules. 

The sticky hemoglobin collects into chains of fibrous strands known as polymers that twist and deform the blood cells. Imagine icicles forming inside a water balloon: The growing ice crystals force the balloon to stretch, twist and eventually burst. Similarly, the deformed blood cells clump together or break open.

When they looked closely, Safo and his collaborators realized that vanillin attached to the hemoglobin and formed a sort of scaffold that held the hemoglobin in shape and kept them from twisting and deforming. 

But vanillin, so promising in early tests, soon looked like a dead end. The difficulty was that vanillin is a chemical compound called an aromatic aldehyde. Most aromatic aldehydes are toxic and the human body has evolved ways to destroy them. Vanillin was torn apart by the body’s enzymes long before it could have any therapeutic effect.

Vanillin was out. Still, the basic idea held promise. Abraham and his team kept looking for similar compounds. Safo found himself deeply interested in the project and continued his work on sickle cell and aldehyde compounds after Abraham retired from VCU in 2007. He modified vanillin into other compounds that show more potent ability to prevent sickling of the red blood cells.

“We went through a few licenses, a few collaborations with pharmaceutical companies and endless conversations with inventors on continuous improvements,” says Innovation Gateway’s Morgan. 

About 10 years ago an unrelated business, Global Blood Therapeutics, demonstrated the power of Safo’s methods. Building on Safo’s published work on vanillin derivatives, the company produced a compound, voxelotor, that was more potent and more stable than prior versions. Voxelotor was approved to treat sickle cell in 2019. 

But voxelotor has a weakness — it does not work in low-oxygen environments. That meant it could not stop blood from sickling in the millions of microscopic capillaries, blood vessels narrower than a human hair that weave throughout the body. 

Meanwhile, gene therapy researchers were having success after studying the genes of a subset of people with sickle cell who have a second mutation that keeps them from developing any symptoms. These therapies worked by teaching the genes of people who have sickle cell disease to re-create that second mutation. But gene therapy is both highly technical and prohibitively expensive, making it of limited use as a treatment on a disease that is most prevalent in sub-Saharan Africa. 

Safo went back to the beginning: vanillin. The researchers knew that aromatic aldehydes formed a sort of scaffold that kept the hemoglobin from sticking together and held the red blood cells in shape. What else could they do?

Safo turned to the technique for which Abraham had first hired him. Using X-ray crystallography, Safo and his team studied the spot where vanillin and their previously studied vanillin derivatives bind to hemoglobin. They realized that these compounds attached next to a section of  hemoglobin known as the F helix that is critical in stabilizing polymers. The F helix locks the hemoglobin together like the couplers that connect train cars, forming those long twisting tendrils. 

An idea arose. What if there were a way to keep those F helix locks from coupling together in the first place? In a sickle-cell polymer chain, “you have it all intertwined together like a zipper,” Safo says. “If you cut any part, the whole zipper is going to fall apart.” 

Safo and the research team — including VCU’s Yan Zhang, Ph.D., and Jurgen Venitz, Ph.D., and Osheiza Abdulmalik, Ph.D., of the Children’s Hospital of Philadelphia — began working to create compounds that would aim to hit the F helix, move it from its locking position and disrupt the formation of polymers.

On their 39th try, they came up with VZHE-039. Like other aromatic aldehyde variations it prevents the hemoglobin from twisting. Unlike previous compounds, including voxelotor, VZHE-039 blocks the F helix locking mechanism, preventing formation of the polymer or breaking it apart. This means VZHE-039 works well in low-oxygen areas like capillaries where other aromatic aldehydes lose their therapeutic activity. And while their earlier promising compound survived only up to an hour in the body, Safo says VZHE-039 lasts for several hours — a requirement for a chronic disease. 

VZHE-039 has been licensed to IllExcor Therapeutics, an incubator associated with the institute where Safo works that is partnering with VCU Innovation Gateway to bring the treatment to the market. Clinical trials are tentatively slated to start in 2022 in England. 

If the testing is successful, Safo says he can envision using the compound to treat millions around the world — including members of his own family in sub-Saharan Africa. 

In May 2021, Safo and the research team received a three-year grant from the National Institutes of Health worth up to $1.7 million to refine the idea and find compounds that bind even more closely to the locking site of hemoglobin polymers. 

Safo, who was inducted into the VCU chapter of the National Academy of Inventors in 2018 for his work, points to Abraham, who founded the institute where Safo works and hired him. “He started it all.” 

Abraham died in April 2021. In a note to fellow faculty after Abraham’s death, Safo wrote simply, “He was a very special person with an incredibly good heart.”