Trials of a new drug called Crizanlizumab offer hope of a breakthrough in pain relief for people with sickle cell disease – the most common of the congenital anaemias.
For the CAN community, we plan a series of articles looking at the problems that patients experience and how research is improving understanding and treatment.
In this first article, we explain why people with sickle cell disease can experience excruciating pain and how the new drug may be able to help. We review the preliminary results and look at the next steps for this research.
Why do people with sickle cell disease experience pain?
Sickle cell disease is a genetic condition that comes about when a child inherits two copies of the sickle cell gene – one from each parent. The red blood cells of patients with sickle cell disease change shape from being round to being long and thin – like the shape of a sickle.
This makes the red blood cells jam together and stops blood flowing properly to some parts of the body. These “traffic jams” in the flow of blood are extremely painful and cause “crises” which may need hospital treatment. Some patients have reported that crises are as painful as child birth and pain management has, for years, been a huge issue in the treatment of sickle cell disease. In addition to being painful, some of the crises are extremely dangerous and can cause strokes or life-threatening complications. If you want to learn more about sickle cell disease please see here.
There are very few drugs for sickle cell disease. The main one is hydroxyurea (also called hydroxycarbamide). This has been available for 30 years, and since then there have been NO NEW DRUGS at all. Partly it’s been lack of research, but also, it’s because the drugs that have been developed just haven’t worked when they have been tested in large clinical trials.
But now, for the first time in 30 years, there is a new drug that looks extremely promising. It is called Crizanlizumab, and the trial showed its results at the 59th ASH (American Society of Hematology) conference in San Diego in December 2016. This work was also published in the New England Journal of Medicine:
How does the drug work?
Blood is made up of red and white blood cells and platelets. Also within blood is a little “flag” called P-selectin that sits on the lining of blood vessels and on some white blood cells and platelets.
For some reason, these P-selectin flags help to tangle up all sorts of blood cells in the “traffic jams” caused by the sickle red blood cells.
Researchers thought if they could hide the flags, the blood might flow better and cause fewer problems. So, this is what Crizanlizumab does – it blocks P-selectin.
How is it given?
It is given as an infusion in the vein, once a month. This is enough to hide the little P-selectin flags almost 100% of the time.
What did the trial show?
The trial took about 200 adult patients with sickle cell disease and split them into 3 equal groups.
Group 1 received a full dose of Crizanlizumab
Group 2 received half a dose of Crizanlizumab
Group 3 received a placebo.
A placebo is something that looks like the drug, but is really nothing active (it is not harmful to give but it also doesn’t carry any benefit). The trial was double-blind, which means neither the patients nor the doctors knew what was receiving the drug and who was receiving the placebo.
At the end of the trial the research showed that:
Patients on the full dose Crizanlizumab had FEWER sickle cell crises per year:
It also took LONGER for patients on the full dose Crizanlizumab to get their next crisis:
The drug was also SAFE with relatively few side effects experienced by the patients. However, the side effects that were reported included fevers, headaches and back pain.
The results of this trial are extremely promising. But this was a Phase 2 trial, which means that it was still limited in patient numbers, and larger trials (Phase 3) may need to be done before the drug gets licensed. It’s difficult to tell at this stage whether that will be necessary or whether the FDA (the US Food and Drug Administration) will license it based just on this trial.
There are a lot of questions that remain unanswered. What are the side effects when this drug is taken long term? Which patients will most benefit from it? Will this drug replace current treatments (hydroxyurea, blood transfusions) or be used alongside them?
However, given the scale of the pain problem in sickle cell and the fact that no new drugs have been produced for 30 years, these findings are extremely important. Finally they offer hope to patients that their excruciating pain may get some relief in the not too-distant-future.