Proportion of participants in the Descartes-08 group compared with placebo who achieve major improvement marked by ≥60 point improvement on the 2016 ACR/EULAR Total Improvement Score (TIS)

Results will be descriptive. Safety and tolerability endpoints will include descriptive statistics of AEs and SAEs. Patients must be followed until all AEs have resolved to Grade 2 or less except for lymphopenia and alopecia.

In Part 3, the primary objective is to compare the effect of Descartes-08 versus placebo, as measured by the change in MGC score from baseline to Week 12. In Part 1, up to three ascending doses of Descartes-08 will be administered to each of 3 to 6 patients; the patients will be staggered at least 21 days apart and will complete a safety review between each dose. In Part 2, patients will receive up to 6 doses in three different schedules depending on the arm they were enrolled into and will be monitored for up to 1 year to assess the safety and tolerability of a repeated dosing schedule.

The primary endpoint for Part-1 is the Maximum Tolerated Dose (MTD), defined as the Dose Level at which no more than 20% of the patients treated have shown Dose-Limiting Toxicity (DLT), i.e. at which 3 patients received all 6 weekly infusions without a DLT by Day 50; or 6 patients received 3 weekly infusions with no more than 1 patient having a DLT by Day 50. The primary endpoint for Part-2 is the type and frequency of treatment-related SAEs. This will be assessed on Days 22, 50 and Months 3,6,9,12

The primary endpoint for Part-1 is the Maximum Tolerated Dose (MTD), defined as the Dose Level at which no more than 20% of the patients treated have shown Dose-Limiting Toxicity (DLT), i.e. at which 3 patients received all 6 weekly infusions without a DLT by Day 50; or 6 patients received 3 weekly infusions with no more than 1 patient having a DLT by Day 50. The primary endpoint for Part-2 is the type and frequency of treatment-related SAEs.