Prof Sergey Nejentsev from the University of Cambridge who led the research that discovered APDS said: "As soon as we understood the cause of APDS, we immediately realised that certain drugs could be used to inhibit the enzyme that is activated in these patients.
Leniolisib does precisely that. I am delighted that we finally have a treatment which will change the lives of APDS patients."
Leniolisib has a list price of £352,000 a year, but was approved as cost effective by the health regulator NICE after the NHS negotiated a substantial, confidential discount.
NICE estimates the drug could benefit up to 50 patients over the age of 12 in England.