CLL is the most common form of leukaemia in Australia and other Western countries. About 50 per cent of people with the disease never develop serious symptoms and don't need treatment.
But the disease is life-threatening for the other half and eventually becomes resistant to chemotherapy.
After one year, overall survival on ibrutinib was 90 per cent, compared with 81 per cent on standard treatment.
"These resistant patients have no other treatment option," says Dr Tam, co-author of a New England Journal of Medicine report on the international trial involving 391 patients.
And unlike chemotherapy, ibrutinib has few side effects. It works by disabling an enzyme crucial for leukaemia's survival.
Patients in the trial responded quickly and reported a greatly improved quality of life, says Dr Tam.
The drug was so effective its superiority was confirmed after an average follow-up of only nine months, and approval of its use in the US has been fast-tracked.
"This pill works extremely well when chemotherapy stops working," says Dr Tam, who participated in the Australian trial.
"The next question is whether this should be the main treatment for leukaemia. We might not need chemotherapy at all."
Hundreds of Australians a year could benefit from the US-developed drug, says Dr Tam.
But Australian approval is around a year away and it could take two years to be listed on the pharmaceutical benefits scheme.
- AAP