PF-07275315

The purpose of this study is to learn about the safety and effects of 2 study medicines (PF-07275315 and PF-07264660) for the treatment of atopic dermatitis (AD). AD is a long- lasting itchy red rash, caused by a skin reaction.
This study is seeking participants who:
* are 18 years of age or more.
* Were confirmed to have AD at least 6 months ago.
* Are not having an effective treatment result from medicines that are applied on skin for AD.
* Are considered by their doctors to have moderate to severe AD.
All participants in the study will receive either PF-07275315 or PF-07264660 or placebo. A placebo does not have any medicine in it but looks just like the medicines being studied.
PF-07275315 or PF-07264660 or placebo will be given as multiple shots in the clinic over the course of 12 weeks.
Stage 1 participants will receive shots at the study clinic on Day 1, Week 1, Week 2, Week 4, Week 6, Week 8, Week 10 and Week 12.
Stage 2 participants will receive shots at the study clinic on Day 1, Week 4, Week 8 and Week 12.
The experiences of people receiving PF-07275315 or PF-07264660 will be compared to people who do not. This will help determine if PF-07275315 and PF-07264660 are safe and effective.
Participants will be involved in this study for up to 40 weeks (20 months). During this time, Stage 1 participants will have 16 visits at the study clinic, and Stage 2 participants will have 12 visits at the study clinic.

The purpose of this clinical trial is to learn about the safety and effects of the study medicine (called PF-07275315) in healthy participants.
This study is seeking participants who:
Are healthy as determined by medical evaluation.
Are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures.
Have a body mass index (BMI) of 17.5 to 32 kilogram per meter square - a total body weight of more than 50 kilograms (110 pounds)
Participants will be divided randomly into 8 different groups. All participants will receive either one PF-07275315 or a harmless treatment that has no medical effect (placebo) intravenous (IV) infusion (given directly into a vein). Participants will take part in this study for up to 541 days. During this time, eligible participants will receive single increasing amounts of PF-07275315 or placebo. Increase will only occur if the sponsor agrees that the next dose is likely to have acceptable safety and tolerability. The follow-up visit will take place 271 days after first treatment.