A Study to Determine the Safety and Efficacy of LX3305 in Subjects With Active Rheumatoid Arthritis

Inclusion Criteria:

• Adult subjects, aged 18 to 75 years

• Active rheumatoid arthritis (RA), class I to III (defined by the American College ofRheumatology), diagnosed at least 3 months prior to Screening

• Minimum of 4 swollen joints (at Screening and Day 1), minimum of 4 tender joints (atScreening and Day 1), and serum C-reactive protein (CRP) level >1.2x the upper limitof normal and/or elevated erythrocyte sedimentation rate (ESR)

• If receiving methotrexate (7.5 mg to 25 mg/week), subject must have been treated forat least 6 weeks prior to Screening and currently receiving a stable dose ofmethotrexate (MTX) with a stable route of administration, and have no plans to changeMTX dose during the study

• Ability to give written informed consent

Exclusion Criteria:

• Women who are pregnant or nursing

• RA diagnosis prior to 16 years of age (juvenile RA)

• Intra-articular and/or parenteral corticosteroids within 4 weeks of study Day 1

• Receipt of live vaccine within 4 weeks prior to Day 1

• Major surgical procedure within 8 weeks prior to Day 1

• Blood donation within 4 weeks prior to Day 1

• Any systemic inflammatory condition

• History of bleeding diathesis

• History of medically significant opportunistic infection

• History of drug or alcohol abuse within 3 years prior to Day 1

• History of cancer within 5 years prior to Day 1

• Presence of hepatic or biliary disease

• History of tuberculosis

• History of human immunodeficiency virus (HIV)

• Any clinically significant laboratory test results, in the opinion of the investigator

• Use of any investigational agent or participation in an investigative trial within 30days of Day 1

• Concurrent use of any biologic agent for the treatment of RA or concomitant diseasemodifying antirheumatoid drugs (other than MTX, hydroxychloroquine, leflunomide, andsulfasalazine - at stables doses for 8 weeks)