The purpose of this program is to assess the safety and efficacy of upadacitinib compared with placebo (fake drug) for the treatment of signs and symptoms in adults with moderately to severely active systemic lupus erythematosus (SLE, also called lupus)

Inclusion criteria:

- Subjects or their legally authorized representative (if required per local regulations) must voluntarily sign and date an informed consent, approved by an independent ethics committee (IEC)/institutional review board (IRB), prior to the initiation of any screening or study-specific procedures.

- Clinical diagnosis of SLE at least 24 weeks prior to Screening as defined by the 2019 EULAR/ACR classification criteria for SLE.

- The subject must be on stable background treatment for ≥ 30 days prior to Baseline (with the exception of oral corticosteroid [OCS], which must be at a stable dose for ≥14 days prior to Baseline)

- Must not have prior exposure to a JAK inhibitor (including Tyk2 inhibitors), including but not limited to commercial upadacitinib (Rinvoq®), tofacitinib (Xeljanz®), ruxolitinib (Jakafi® or Opzelura®), baricitinib (Olumiant®), peficitinib (Smyraf®), abrocitinib (Cibinqo®), filgotinib (Jyseleca®), fedratinib (Inrebic), and deucravacitinib (Sotyktu®).