A First-in-human Study of KT501 Administered Subcutaneously to Patients With Rheumatoid Arthritis (RA).

This is a Phase 1, open-label, first-in-human dose escalation study to investigate the safety, tolerability, pharmacokinetic and pharmacodynamic of KT501 by a single subcutaneous administration in participants with Rheumatoid Arthritis (RA).

Up to a total of 5 cohorts with up to approximately 24 participants in total with RA will be enrolled. All participants will receive a single dose of KT501 on Day 1 and followed up until Week 12. For any participants with B cells lower than baseline level or lower limit quantification, whichever is lower, additional B cell follow up is required up to Week 48 after the study treatment.

Inclusion criteria

• 18 to 75 years old
• Diagnosis of adult-onset RA for at least 6 months
• Moderately to severely active RA
• Inadequate treatment response as defined in the protocol
• RF + or ACPA+
• Stable use of traditional DMARDs is permitted
• Willing and able to comply with all study assessments and adhere to the protocol schedule and restrictions.

Exclusion criteria

• Functional class IV as defined by the ACR Classification of Functional Status in RA
• Presence of any concomitant autoimmune disease other than RA
• Active infection, history of serious recurrent or chronic infection
• History of progressive multifocal leukoencephalopathy
• Have a diagnosis or history of malignant disease within 5 years or breast cancer diagnosed within the previous 10 years.
• History of or planned organ transplant and/or autologous or allogeneic hematopoietic stem cell transplantation
• Receipt of live vaccine within 4 weeks
• Major surgery (including joint surgery) within 8 weeks prior to screening or planned major surgery within 6 months after study
• Women who are pregnant or breastfeeding
• Significant or uncontrolled medical disease that would preclude participant participation