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Cell & Gene Therapy Insights

BioMarin shares drop as the durability of its hemophilia A gene therapy remains ‘doubtful’

Latest update from BioMarin’s ongoing Phase 1/2 and Phase 3 gene therapy trials has raised concerns among investors and they are doubtful whether the gene therapy has the potential to ‘cure’ hemophilia A.

BioMarin’s gene therapy uses an adeno-associated virus (AAV) vector to deliver the human blood clotting gene, FVIII, to patients with severe hemophilia A, an X-linked bleeding disorder caused by deficiency of the clotting protein, FVIII. Bleeding-related complications often result in greater severity of disease, poor quality of life, surgical interventions for severe joint destruction and shortened life span.

With a potential price tag of more than US$1 million, this gene therapy, called valoctocogene roxaparvovec, is one of several gene therapies under development that has claimed to cure hemophilia permanently following a one-time gene delivery.

The Phase 1/2 trial has followed eight patients for three years. Two doses of the gene therapy were tested and on average, patients who received the high dose, saw a 96% decline in bleeding episodes over three years. At the low dose, the hemophilia A treatment cut bleeding episodes by an average of 92%.

Based on the study data, the company reported that the treatment’s impact declined at first, then plateaued in the second year before declining more slowly over time but remains effective for up to eight years. The company said over time, it may find that the treatment lasts longer. The company is now exploring options on how to give patients a second dose of the treatment if its efficacy wanes. The company said the data showed a dramatic reduction in patient need for protein infusions.

BioMarin also released data from a second trial, a Phase 3 study conducted in 20 patients. Eight out of twenty patients who received the treatment 23-26 weeks ago were followed for about six months. Data thus far showed that patients experienced an average of 1.5 bleeding episodes — an 85% reduction from before receiving the gene therapy.

But investors are underwhelmed and as data thus far reveals, the effect of the therapy is doubtful as many patients had to receive clotting protein infusions several times a week in order to avoid bleeding and one patient in the study resumed these regular infusions.

Shares of the company dropped down 5per cent to US$84.50 following the news. According to Josh Schimmer, an analyst, the data “update indicates durable benefit beyond 3 years for most patients, but doesn’t seem to have the legs to look like a true ‘cure’.

Source: BioMarin says data shows hemophilia gene therapy effects could wane; Press Release

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