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A Gene Therapy Timeline

More than 100 years ago, scientists started unlocking the mysteries of genes and inherited traits. Today, gene therapy holds promise for conditions like hemophilia B.

Timeline of gene therapy milestones, including on an outsized, horizontal DNA strand that is serving as a path people are walking on.

Gene therapy is the first medical treatment to address underlying issues within our DNA, the genetic material inside our cells – and it is rapidly transforming formerly incurable conditions into manageable ones. Building on more than a century of scientific discovery, gene therapy is now a well-established form of medication with more than 10,000 individuals treated by various gene therapy products.

See a recent news release about a hemophilia B gene therapy study shared at the European Association of Haemophilia and Allied Disorders (EAHAD) 2022 Annual Meeting.

It was nearly 120 years ago that scientists realized that the traits we inherit from our parents not only give us certain hair and eye colors, but also give some children the exact same metabolic conditions as their parents. It was then, along with the subsequent discovery of the DNA structure in the 1950s, that confirmed that DNA was the molecule that transmitted those instructions to offspring. DNA is a set of step-by-step instructions that cells use to make proteins we need to survive and live healthily. 

However, there are times when the DNA we have is altered and prevents our cells from making fully functional proteins, which can undermine our health and cause conditions such as hemophilia. Gene therapy is an innovative, transformative treatment approach that aims to address these underlying genetic mutations to treat or cure a condition.    

The very first attempts at gene therapy for a metabolic disease began in 1970. While the attempt failed to make the desired changes, scientists gained valuable knowledge and the science advanced rapidly, as did the regulatory oversight of the technology to ensure the safety of patients. It now takes approximately seven to 10 years of study in labs and carefully controlled clinical trials in humans to prove a gene therapy is safe and effective.

In 2007, gene therapy hit its stride as scientists identified that “vectors” served as the best vehicles for delivering new genes into cells as they excel at getting into specific targeted cells – a feature that makes them ideal for situations where a specific tissue or organ is the cause of a disease. Therapeutic vectors being used in research are commonly made from adeno-associated viruses (AAVs). Currently, there are more than 250 AAV-based clinical trials underway across a variety of conditions, including hemophilia B.

Due to a mutation in the F9 gene, people with hemophilia B do not produce sufficient levels of Factor IX (FIX), a protein that helps the blood form clots to stop bleeding. Gene therapy offers great promise in replacing the single altered gene to allow the body to generate its own stable levels of FIX in the liver. In clinical trials, AAV-based gene therapy in hemophilia B has produced stable FIX activity for over eight years of follow-up with sustained decreases in annualized bleed rate (ABR) and FIX replacement therapy.

In 2020, CSL Behring acquired global rights to commercialize an investigational AAV-based gene therapy, which is being evaluated in the ongoing HOPE-B clinical study now in Phase 3.

To learn more about the steps that have led to the evolution of gene therapy for hemophilia B, visit