Multiple Ascending-Dose Study of XmAb®27564 in Patients With Psoriasis or Atopic Dermatitis

Inclusion Criteria: The main inclusion and exclusion criteria include, but are not limited to, the following: * Have active mild-to-severe plaque psoriasis or moderate-to-severe atopic dermatitis according to study-specific criteria * Weight between 40 to 150 kg, inclusive * No topical treatments for psoriasis or atopic dermatitis for 2 weeks before randomization * No phototherapy for psoriasis for 4 weeks before randomization * Washout of oral treatments for psoriasis or atopic dermatitis for 4 weeks before randomization * Washout of biologic treatments for psoriasis or atopic dermatitis for 12 weeks before randomization * Stated willingness to comply with all study procedures (including skin biopsies) and availability for the duration of the study Exclusion Criteria: * Patients with a history of active asthma within 5 years of screening, except those that have well controlled asthma symptoms at screening visit. * Patients who have had any prior investigational treatment with IL-2 therapies