Dataset from A Randomized, Double Blind (Sponsor Open), Comparative, Multicenter Study to Evaluate the Safety and Efficacy of Subcutaneous Belimumab (GSK1550188) and Intravenous Rituximab Co-administration in Subjects With Primary Sjögren's Syndrome

This study is a multi-national, multi-center, double-blind (sponsor open), randomized,
placebo-controlled trial in subjects with active primary Sjögren's syndrome designed to
understand the safety and tolerability profile of belimumab/ rituximab co-administration and
of belimumab monotherapy; and to evaluate whether either co-administration therapy or
belimumab monotherapy has a substantive effect on disease activity.

This study will consist screening period, double blind treatment period, a general follow-up
period and individualized follow-up period. Approximately 70 subjects will be recruited into
the study initially. At Day 0, subjects will be randomized 1:2:2:2 to one of the four
treatment arms placebo arm, belimumab monotherapy arm, co-administration therapy arm and
rituximab monotherapy arm. Once a sufficient number of subjects have completed the Week 24,
interim analyses and sample size re-estimation will be conducted. The total number of
subjects randomized may increase following sample size re-estimation up to a maximum of 120
recruited into the study.

Subjects in all arms will receive investigational product (IP) until Week 52 (completion of
the treatment phase). All subjects will enter a 16-week general follow-up period after the
Week 52 visit or after discontinuation if a subject discontinues IP and withdraws from the
treatment phase visits prior to Week 52.

After completing the general follow-up period, subjects with cluster of differentiation
(CD)19+ B-cell levels below the lower limit of normal (or less than 90 percent [%] of
baseline, if baseline value was below lower limit of normal [LLN]) will enter an
individualized safety follow-up phase and return to the clinic for visits every 12 weeks with
monthly calls between visits to evaluate subjects for any serious adverse events (SAEs)
related to IP or study participation, fatal SAEs, and designated adverse event of special
interests (AESIs) (i.e., infections, malignancies, or depression, suicide/self-injury), and
to check concomitant medications.

The total duration of participation of a subject in this study will be approximately up to a
maximum of 2 years (i.e., up to Week 104).