BRUSSELS (Reuters) – Belgian drug developer Ablynx said on Monday its top drug, arthritis treatment ozoralizumab, had shown a benefit over its biggest rival in the $24 billion market for this class of treatment.

The company, which makes ultra-small antibodies derived from llamas, said data showed few patients developed immunity to the drug, a problem which can affect its biggest rival Humira, produced by U.S. based Abbott Laboratories.

“We believe that we now have the components of a much stronger and differentiating licensing package than we had previously,” Ablynx Chief Executive Edwin Moses said in a statement.

It said the study, an expansion to a previous phase II trial, showed that less than 1 percent of patients had antibodies at the end of the treatment period.

Abbott Laboratories has said antibodies developed in about 5 percent of adult rheumatoid arthritis patients who take Humira.

Ablynx is in partnership discussions for ozoralizumab, which it said it hopes to conclude at the end of this year.

“If your question is ‘does this have impact on partnering discussions’, yes, because they come with a stronger data package and there is some potential for differentiation,” says KBC Securities analyst Jan De Kerpel.

It’s previous partner, U.S. based Pfizer, handed back rights to the drug last year, sending Ablynx’s shares down as much as 21 percent.

(Reporting by Ben Deighton; Editing by Mark Potter and Mike Nesbit)