Gene Therapy Treatment Surprisingly Useful In Four Hemophiliac Patients

12.13.11 7 years ago

Google image searching “hemophilia” is horrifying, so here’s a cat checking her blood pressure instead.

Hemophilia B has now become the first widespread disease successfully treated by gene therapy. There have been some successes with rarer diseases, but most gene therapy studies so far have failed either because the virus used to carry the replacement gene is killed too quickly by the patient’s immune system or because the therapy increased the risk of cancerous mutations.

Hemophilia B is an X-linked bleeding disorder which affects an estimated 1 out of 30,000 males born in the U.S. (women can only have the disease if they inherit an affected X chromosome from both parents, an unlikely but not impossible scenario). It was carried by Queen Victoria and was the type of bleeding disorder common in European royalty. It’s about one-fifth as common as Hemophilia A, however, Hemophilia B was chosen for the study because the effected gene is smaller and easier to manipulate. The effected gene causes the expression of Factor IX (FIX), a blood clotting factor, to drop to 1% or lower the normal expression.

As reported in the New England Journal of Medicine, Dr. Amit C. Nathwani and his team at University College London used a delivery virus prepared at St. Jude Children’s Research Hospital on six patients with Hemophilia B. The virus carries a replacement for the FIX gene and inserts it into cells of a hemophiliac patient’s liver, avoiding the chromosomes to lower the likelihood of cancerous mutations.

After treatment, all six patients’ FIX levels rose to between 2% and 12%, which may not seem like much compared to their usual 1% or lower levels, but four of the six patients have not required any of their usual intravenous FIX treatments for up to 22 months since undergoing the experimental gene therapy. Treating patients with intravenous FIX derived from blood donors costs an estimated $300,000 per year per patient. The gene therapy injection costs $30,000. If the effects of the injection prove to be permanent, it’s a tremendous money and time saver for patients. Unfortunately, it’s possible that the treated liver cells will eventually be replaced by new liver cells with the FIX mutation still present, and a patient can sometimes only be given one injection, as their immune system can too easily mount an attack on the carrier virus after the first exposure.

The patients will be monitored closely for any signs of liver cancer and for the long-term effectiveness of the therapy. The team is going to treat 20 more Hemophilia B patients in an attempt to find the highest dose which can be given in a single injection without prompting an immune system attack. Dr. Edward G. D. Tuddenham, director of the Hemophilia Center at the Royal Free Hospital in London, said the treatment “could be available for widespread use in a couple of years.”

I realize I didn’t put any jokes in this post, so I’ll just say this: Brits spell hemophilia weirdly. They spell it “haemophilia”. What haomos.*

* I’m allowed to say that. I asked for permish at the secret agenda meetings.

[Sources: NEJM, Medgadget, NYTimes, UCL, 80beats, EpicPonyz]

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