A medicine to treat lupus has proved effective in a large clinical trial, and could be on the way to becoming the first new treatment for the disease in more than 40 years.

Lupus is a complex autoimmune disease in which the immune system attacks a person's own tissues, damaging joints, skin and other organs. Affecting primarily women of child-bearing age, lupus can cause rashes, arthritis, kidney damage and other problems.

Lupus patients have generally had to rely on immune suppressants and steroids to treat their disease. But steroids can cause severe weight gain, acne and bone weakening, among other side effects.

Now, the Phase 3 trial on a drug that "calms" the immune system, called Benlysta and known generically as belimumab, offers new hope.

The study involved 865 patients on standard steroid-based lupus therapy. One-third were also given a high dose injection of Benlysta, one-third a low dose, and one-third received a placebo.

After one year, 58 per cent of patients on high-dose Benlysta experienced a significant improvement in symptom severity, compared with just 43 per cent of those on placebo.

Patients taking Benlysta also had fewer disease flare-ups, fewer severe flare-ups, and a longer time between flare-ups. They also reported less fatigue and better quality of life. Of particular note, more patients taking Benlysta were able to reduce their steroid dose.

Previously reported findings from the study showed the drug is also more effective at reducing pain, hair loss, and skin rash than placebo.

The most common side effects from the drug were headache, muscle pain, upper respiratory tract infections, urinary tract infection, and influenza, but were comparable between the three treatment groups. Serious infections were reported by about six percent of patients in all three groups.

Dr. Sandra V. Navarra, head of rheumatology at the University of Santo Tomas, Manila, Philippines, reported the findings at the 73rd Annual Scientific Meeting of the American College of Rheumatology.

Human Genome Sciences Inc. and GlaxoSmithKline, which are developing the drug, funded the study. The results have not yet been published or peer-reviewed by independent experts.

Finding an effective medication for lupus has been difficult because the disease's symptoms come and go and vary considerably from one patient to another.

Data from Phase 2 of studies on Benlysta suggested the drug helped only 8 to 14 of every 100 patients treated. But because its side effects are relatively mild and it has the ability to reduce steroid use, it is likely to be attractive to patients and their doctors.

Benlysta works by inhibiting the action of a protein in the body called B-lymphocyte stimulator, which helps B cells in the blood respond to infections. It's thought that high levels of the protein spur the immune system to attach the body's own tissues.

Results of another large trial comparing Benlysta against standard care are scheduled to be released next month. If the drug works well, the companies plan to apply for FDA approval in the U.S.