Mid-stage data on a little-known drug from Galapagos for rheumatoid arthritis has caused a stir.

Last week, the Belgian drugmaker released data from a Phase II study of GLPG0634,  which showed that the Janus kinase (JAK)-1 inhibitor  achieved the primary endpoint of significant improvement in the signs and symptoms of RA. The 36-patient trial lasted for four weeks and 83% of patients showed improvement in ACR20 levels at just four weeks.

GLPG0634 was well-tolerated, with all patients completing the trial and no anaemia or increases in lipids were observed. No severe adverse events were reported.

Piet Wigerinck, head of development of Galapagos, said that "despite the short duration of the trial, GLPG0634 shows one of the highest initial response rates ever reported for RA treatments". If this efficacy and safety profile is maintained in longer studies, the drug "has the potential to become a blockbuster treatment for RA and other inflammatory diseases”, he added.

Galapagos expects group revenues of 146 million euros for 2011 and positive operational and net earnings. However it notes that "this guidance will only be achievable in the event the GLPG0634 programme is successfully partnered before year-end". The Mechelen-based firm is in discussions with a number of drugmakers but "has not yet decided whether or not to partner, and on which conditions".

Galapagos stock leapt around 22% on the news and analysts at Edison Investment Research issued a note saying that "this has pitched this hitherto almost unknown compound squarely into the high-profile oral disease-modifying anti-rheumatic drugs (DMARD) space behind the two potential blockbusters of Pfizer’s tofacitinib and AstraZeneca’s fostamatinib".

In terms of partnering, Edison says it appears that Galapagos "may have had an option-based offer on the table, but it probably makes more sense to retain rights and conduct further studies".