A Study to Learn About a Medicine Called PF-08154225 in Participants With Autoimmune Diseases

A PHASE 1/2, MULTI-CENTER, OPEN-LABEL, SINGLE- AND MULTIPLE-DOSEESCALATION, DOSE EXPANSION STUDY TO EVALUATE THE SAFETY, TOLERABILITY, PHARMACOKINETICS, PHARMACODYNAMICS AND PRELIMINARY EFFICACY OF PF-08154225, IN PARTICIPANTS WITH AUTOIMMUNE DISEASES INCLUDING ACTIVE SYSTEMIC LUPUS ERYTHEMATOSUS (SLE), OR RHEUMATOID ARTHRITIS (RA), OR IDIOPATHIC INFLAMMATORY MYOSITIS (IIM) OR SYSTEMIC SCLEROSIS (SSC)

The purpose of this study is to learn about the safety and effects of the study medication called PF-08154225 for the potential treatment of autoimmune diseases. An autoimmune disease is a condition that makes a person's immune system attack its healthy cells by mistake. This study is particularly looking at autoimmune diseases called as Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA), Idiopathic Inflammatory Myositis (IIM) or Systemic Sclerosis (SSc).

This study is divided into 3 parts: Part 1a, Part 1b and Part 2. Parts 1a and 1b are seeking participants with Systemic Lupus Erythematosus (SLE) or Rheumatoid Arthritis and Part 2 with also Idiopathic Inflammatory Myositis (IIM) or Systemic Sclerosis (SSc).

Participants can take part only in one part of the study.

All participants in this study will receive PF-08154225 at the study clinic. In Part 1a participants will receive single administration of PF-08154225 after which they will be observed at the study clinic during regular visits through week 16 or longer.

In Part 1b the participants will receive multiple administration of PF-08154225 after which they will be monitored in similar a manner as in Part 1a through week 24 or longer.

In Part 2 participants will receive multiple administrations of PF-08154225. After the last injection they will be monitored for safety through week 52 or longer.

Select Inclusion Criteria

1. At age between 18 and 70 years at Screening.
2. Confirmed diagnosis of RA according to the 2010 American College of Rheumatology (ACR)/ European Alliance of Associations for Rheumatology (EULAR) criteria at Screening, with symptom at least 6 months prior to Screening
3. Clinical diagnosis of SLE according to the 1997 ACR Criteria for the Classification of SLE Or confirmed diagnosis of SLE according to the Systemic Lupus International Collaborating Clinics (SLICC) Classification Criteria at Screening, with symptom at least 6 months prior to Screening.
4. Clinical diagnosis of 1 of the 3 IIM subtypes based on phenotype, and/or prior muscle biopsy, and positive myositis-specific autoantibody (MSA) / myositis-associated antibody (MMA)
5. Classification of SSc according to the 2013 ACR/EULAR criteria at Screening

Select Exclusion Criteria

1. Any medical or psychiatric condition, including active suicidal ideation or any laboratory abnormality, that increases study risk or makes the participant unsuitable.
2. Active central nervous system (CNS) co-morbidity
3. Any complications of disease under study that in the judgement of the investigator may be life or organ threatening or require prohibited medication
4. Known history of a primary immunodeficiency, splenectomy, or any underlying condition that predisposes the participant to infection
5. Active or recent clinically significant infections
6. Chronic or active Hepatitis B and C
7. Past or current therapies with T-cell engager (TCEs), bone marrow cell transplant, stem cell transplant, chimeric antigen receptor T-cell (CAR-T) cell therapy.
8. For SLE, no catastrophic or severe antiphospholipid syndrome (APS), severe unstable neuropsychiatric SLE.
9. Felty's syndrome, juvenile arthritis or idiopathic arthritis before age of 16
10. SSc renal crisis within 6 months prior to screening, UIP pattern if entering on interstitial lung disease interstitial lung disease (ILD) criteria
11. Diagnosis of Inclusion body myositis (IBM) and Usual interstitial pneumonia (UIP) pattern if entering on ILD criteria