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An uncharted pathway

Some of the greatest advancements in modern medicine started with a scientist taking a risk to boldly pursue new areas of research. For scientists at Alexion — a leading biotech company dedicated to treating rare diseases — that risk involved an extraordinary research journey to discover molecules that selectively target and inhibit the complement system, a part of the immune system that is essential to the body’s defense against infection.

In the beginning, this approach wasn’t widely understood or readily accepted. A belief in the science and a drive centered around patient safety enabled the company to move from a hypothesis to a potential medicine for a rare disease. The Alexion team’s vision was realized when the FDA approved the first complement inhibitor medicine in 2007 as a treatment for a single rare disease, but in many ways, the journey had just begun.

“Alexion’s success was born out of a unique experience — our team uncovered groundbreaking research that sparked a new way of understanding and approaching some rare diseases,” said Sharon Barr, Ph.D., Senior Vice President, Head of Research, Bioinformatics and Diagnostics at Alexion. “With compelling evidence that complement inhibition had the potential to treat one devastating disease, the team felt an immense responsibility to themselves, to other scientists in the field and most importantly to patients, to double down on its research efforts and seek out other diseases where complement inhibition might work too. We knew we had only scratched the surface.”

The drive to explore further

Cracking the science of complement biology for one rare disease energized both Alexion and the scientific community. It sparked curiosity and a hunt to identify other diseases where complement dysregulation may also be involved.

When experts and academics approached the company with emerging data on the role of complement biology in a neurologic disease, Alexion once again followed the science. After initiating a first-of-its-kind trial, they uncovered the potential of complement inhibitors in treating this rare neurologic disease that had limited treatment options at the time.

Emboldened by compelling findings and real-world evidence, the scientists at Alexion and experts across academia continued their research exploration in complement dysregulation. Soon after, new insights led to a clinical trial that demonstrated the potential for targeted complement inhibition in a second rare neurologic disease.

“When I first read about the findings in this rare neurologic disease, I was astonished. I had never seen a data set like this in my career.”

Laura Gault, Vice President, Neurology Clinical Development at Alexion

“Over time, Alexion, along with support from other complement researchers, has amassed a huge amount of knowledge and experience that enables us to design impactful clinical trials, adapting as we go to deliver answers with the goal of bringing forward new transformative treatments for patients living with rare diseases and devastating conditions,” said Gault.

Today, Alexion’s first complement inhibitor is now approved for four indications, spanning hematology, nephrology, and neurology, and the company has obtained approval of a second complement inhibitor with hematology and nephrology indications. 

Just the beginning of the journey

For nearly three decades, Alexion researchers have been a driver for discovery and development in complement inhibition, and their journey is not yet complete. Those early, game-changing results inspire a relentless hunger to uncover the full potential of complement inhibition as a treatment approach. Through exploration of new targets and even more diseases, including conditions involving the eyes, kidneys and nervous system, they are continuing to blaze a purpose-driven path.

“We take a very thoughtful approach to determining which research areas to pursue next. This includes studying each individual disease and looking at the specific pathways involved to determine how best to explore complement inhibition to treat the underlying biology of a condition,” said Sung-Kwon Kim, Research Investigator, Pharmacology and Translational Research at Alexion. “These details, combined with the right scientific tools, help the team to make smart research decisions and ultimately deliver innovative solutions for some of the hardest-to-treat diseases.”

What began as a bold step into the unknown, ultimately paved the way for a new class of medicines. And this is not the end of the road — in fact, it is just the beginning.

To learn more about Alexion’s work in complement inhibition, visit