An Ascending Dose Study of PIT565 in Participants With Systemic Lupus Erythematosus (SLE).

Inclusion Criteria:

* Diagnosis of SLE according to the 2019 ACR/EULAR criteria
* Documentation of SLE autoantibodies
* Active SLE disease, as demonstrated by a SLEDAI-2K ≥ 4 at screening
* Failure to respond to standard-of-care medicines for the treatment of SLE as detailed in the protocol
* Immunization against pneumococcus, influenza, and COVID-19

Exclusion Criteria:

* Severe SLE-related organ damage dysfunction or life-threatening disease at screening.
* Any acute, severe lupus-related flare during screening that needs immediate treatment such as acute CNS lupus (e.g., psychosis, epilepsy) or catastrophic antiphospholipid syndrome.
* Presence of severe lupus kidney disease as defined by worsening proteinuria or estimated glomerular filtration rate (eGFR) which in the opinion of the Investigator requires immune-suppressive induction or maintenance treatment at screening.
* History or current diagnosis of ECG or cardiac abnormalities indicating a significant risk of safety for participants.
* Use of prohibited medication defined in the protocol.
* Clinically significant active, opportunistic, chronic or recurrent infection (including, HIV, HBV, HCV) confirmed one month prior to or during screening.
* Serious medical illness likely to interfere with participation in this clinical study.
* Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant unless they are using highly effective methods of contraception

Other protocol defined inclusion/exclusion criteria mat apply.