Clinical trial results described as "striking and exciting" could lead to new treatment options for rheumatoid arthritis.
The antibody drug tocilizumab was almost four times more likely to halt progression of the condition than the most widely prescribed alternative.
It also achieved significantly greater reduction in disease signs and symptoms after six months.
Scientists compared tocilizumab, marketed as RoActemra, with the "anti-TNF" drug adalimumab (Humira).
The drugs were tested in a group of 326 patients unable to take the mainstay treatment for rheumatoid arthritis (RA), methotrexate (MTX)
MTX is ruled out for roughly a third of patients, many of whom suffer unbearable side effects such as vomiting, hair loss and mouth ulcers.
Currently, such individuals generally move onto anti-TNF drugs, which target a molecule called tumour necrosis factor that promotes inflammation.
Tocilizumab works in a completely different way by targeting another inflammatory protein, interleukin six (IL-6).
Consultant rheumatologist Professor Paul Emery, from the University of Leeds, who took part in the Adacta trial, said: "These results are impressive and important for the 30% of patients with RA who cannot take methotrexate.
"In RA, disease remission is the goal of therapy.
"However, for varied reasons, many patients fail to achieve this goal.
"Adacta, which compared two active biologics as monotherapies (in methotrexate intolerant patients), has produced striking results and the results help in choosing the right drug for the right patient."
The findings were presented in Berlin at Eular, the annual meeting of the European Congress of Rheumatology.
Professor John Isaacs, a rheumatology expert from the University of Newcastle, said: "These results are very important and exciting.
"For the tens of thousands of patients in the UK that can't take methotrexate, RoActemra will offer them an increased chance of remission, which is the ultimate goal of rheumatoid arthritis treatment.
"This study is the first time a treatment has gone 'head to head' with an anti-TNF in this setting, and to show a significant increase in patients achieving remission is very impressive."
At £9,500 per patient per year, RoActemra costs about the same as Humira.
The NHS cost-effectiveness watchdog Nice (National Institute for health and Clinical Excellence) has already approved of RoActemra when combined with methotrexate.
The new results may lead to the drug being given to larger numbers of patients on its own.
An estimated 646,000 people in the UK have RA, a painful and disabling condition caused by the immune system attacking the joints.
Of those newly diagnosed, around a half will be unable to work within 10 years.
Ailsa Bosworth, chief executive of the National Rheumatoid Arthritis Society, said: "With any medical condition, remission is the number one target. Curing the person of their illness and enabling them to get on with their life is the ultimate goal.
"For those with rheumatoid arthritis however, there is no cure, they will always have rheumatoid arthritis. Remission for those with RA does not mean the disease has gone, it just means it is better controlled.
"The key to the most successful outcome is an early diagnosis and early treatment with the most effective drug(s)."
- John von Radowitz
