The first new treatment for lupus in a half-century has won US approval, a milestone for patients with the disabling disease and a potential blockbuster for its tiny biotech maker.

Health officials cleared Benlysta, discovered by Human Genome Sciences, to combat the disease that causes the immune system to attack joints and organs and has proved tough to study and treat.

Shares of Human Genome, a money-losing company founded in 1992 to develop drugs with data from the human genetic map, were halted. The company will split profits with British drug giant GlaxoSmithKline.

Glaxo shares rose 3.4 per cent in after-hours trading to $39.90, up from an earlier close of $38.58 in regular trading on the New York Stock Exchange.

Benlysta's annual global sales may top $3 billion in 2015, according to Thomson Reuters consensus forecasts. Some analysts predict sales as high as $5 billion in later years.

For doctors and patients, Benlysta is a welcome advance after decades with few good options and a string of research failures.

"It is a big success. It opens the way for more FDA-approved lupus drugs," Dr. Anca Askanase of the New York University School of Medicine and the NYU Hospital for Joint Diseases said in an interview.

The Food and Drug Administration approved Benlysta for certain patients with active lupus who are receiving standard therapy.

It said black patients "did not appear to respond to treatment" with Benlysta in clinical trials but added that studies "lacked sufficient numbers to establish a definite conclusion."

The FDA did not warn against use in black patients, as some investors feared, but instead required the company to run a post-approval study in blacks.

Important new treatment

Use is not recommended for patients with lupus that has caused severe kidney or central nervous system problems, the makers said in a statement.

More deaths and serious infections were reported with Benlysta compared with a placebo in clinical studies. The FDA required a patient-friendly guide explaining the risks.

"Benlysta, when used with existing therapies, may be an important new treatment approach ...to help manage symptoms," said Dr. Curtis Rosebraugh, head of the FDA office that reviewed the drug.

Lupus causes a range of symptoms including arthritis, kidney damage, chest pain, skin rashes, severe fatigue and other problems. Symptoms often wax and wane. The organ damage can be fatal.

An estimated 5 million people worldwide have the disease.

Current drugs often fail to help or cause harsh side effects, such as severe bone loss from steroids.

"That is what makes it really important with Benlysta - the possibility of having a successful treatment that is less toxic than the drugs we normally use. They can really play havoc on the body," said Benjamin Pruitt, a 50-year-old educator and musician from Falls Church, Virginia, who has been living with lupus for over 25 years.

Relief with no organ damage

One company-funded study showed 43 per cent of patients given a high Benlysta dose with standard therapies felt relief and had no further organ damage after one year of treatment.

That compared with nearly 34 per cent with a placebo and standard care, which includes immunosuppressant drugs such as Roche's CellCept and steroids such as prednisone.

The drug will cost the average patient about $35,000 annually, a price in line with other biotech medicines for autoimmune diseases, Barry Labinger, Human Genome's chief commercial officer, said on a conference call.

The companies expect Benlysta will be available in about two weeks.

Benlysta has revived Human Genome, a company that struggled to capitalize on excitement about the mapping of the human genome.

Several of the company's drugs failed in clinical trials, and investors largely wrote off Benlysta after mixed early data. Its shares fell below 50 cents in March 2009 but jumped later that year when the first encouraging Benlysta data was released.

Now, the company is an industry star and takeover target for partner Glaxo or other big drugmakers, analysts said.

Benlysta, known generically as belimumab, is given once a month by intravenous infusion.

Sanford Bernstein analyst Geoffrey Porges said the product could reach $2 billion in sales by 2015 or later. "But they are going to have to ramp up production of the product pretty quickly. The initial adoption is going to be fairly modest this year," he said.

The company expects European approval for the drug in the second half of the year. – Reuters