A Study to Assess the Efficacy, Safety and Tolerability of DDY391 in Participants With Moderate to Severe Psoriatic Arthritis

This study is a Phase 2a/b, randomized, double-blind, placebo-controlled, multicenter trial designed to evaluate the efficacy, safety, tolerability and dose-response relationship of DDY391 in participants with active moderate to severe PsA. The study is composed of two sequential parts: * Part A to evaluate efficacy, safety and tolerability of DDY391 compared with placebo. * Part B to determine the dose-response relationship of multiple doses of DDY391 compared with placebo.