Eculizumab and ravulizumab are both successful treatments for PNH. They work by binding to and blocking the activity of a protein called C5, which eases the destruction of red blood cells in the blood stream.
Most people who take the treatment do really well, but a minority experience an issue called ‘extravascular haemolysis.’ This occurs when red blood cells are broken down prematurely within the liver and spleen. Whilst not life threatening, it can make people become tired and anaemic, and sometimes, transfusions are needed. For them, there is an alternative drug, called pegcetacoplan.
Pegcetacoplan, which was authorised for use in the UK in 2022, works by targeting a different part of the immune system, called C3. This helps to control the breakdown of red blood cells inside blood vessels, and to prevent the development of extravascular haemolysis.
The drug proved its worth in a handful of clinical trials, and in this 2024 study, Christopher Patriquin and colleagues looked at what happened to 137 patients who continued to take pegcetacoplan for a year or so after the trials had stopped.
During this time, the treatment continued to work well. The patients weren’t anaemic or fatigued. They had normal levels of lactate dehydrogenase (LDH), which is an indication that their red blood cells were not being destroyed. They didn’t develop blood clots, and the majority of patients did not require a red blood cell transfusion.
The study showed that pegcetacoplan is safe and effective to take over the longer term. It’s now used for PNH patients who have been on a C5 inhibitor for more than three months, but who still remain anaemic. It is given, at home, as a twice weekly injection under the skin, which the patients administer themselves.