A Study In Adults With Moderate To Severe Dermatomyositis

Inclusion Criteria for Patients with Skin Predominant Activity:

• Must have CDASI Activity score of greater than or equal to 14, and have failed at least 1 standard of care systemic treatment, (eg, corticosteroids).

• Confirmation of DM by the investigator and two of the following:

1. Gottron's papules;

2. Gottron's sign;

3. Heliotrope eruption;

4. Nailfold changes, (dilated capillary loops, capillary dropout, cuticular hypertrophy and/or rugged cuticles;

5. Photodistributed violaceous erythema, (skin that is exposed to sunlight and appears purplish/reddish, and patchy in appearance;

6. Positive DM serology -

• Post DM diagnosis; standard of care workup for DM must have been completed prior to entry into this research study.

• Willing to provide 8 biopsies during the course of the research study

Inclusion Criteria for Patients with Muscle Predominant Activity:

• MMT-8 ≤136/150 and PhGA, VAS ≥3 cm (0-10 cm) by visual analog scale (VAS)

• Sum of PhGA, VAS, PtGA, and extramuscular global assessment VAS scores is ≥10 cm (0-10 cm) VAS for each.

• Participant has failed at least two or more adequate courses of an immunosuppressive agent or immunomodulatory agent, including IVIG, at a dose known to be effective for rheumatologic diseases.

Exclusion Criteria for Patients with Skin Predominant Activity:

• Investigator site staff or members of their family.

• Acute and Chronic present medical conditions

• Intake of greater than 15 mg of prednisone or equivalent per day

• Pregnant or breastfeeding females. Fertile men and women who will not comply with the use of 2 effective birth control methods as per the research protocol

• Have required management of acute or chronic infections

• Have pre existing demyelinating disorder such as multiple sclerosis, or other severe neurological deficits.

• Clinically significant lab abnormalities

• Any health condition that may be worsened by immunosuppression

Exclusion Criteria for Patients with Muscle Predominant Activity:

Similar to patients with skin predominant activity; Intake of >20 mg oral prednisone/day, or equivalent