Trial of IMO-8400 in Adult Patients With Dermatomyositis

This study will evaluate the safety and efficacy of IMO-8400 in adults with active
dermatomyositis (DM).

Inclusion Criteria:

- Has definite or probable DM based on the criteria of Bohan and Peter

- Has a Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI)-Activity score
≥15

- Patients with muscle weakness are eligible; however having muscle weakness is not
mandatory.

- Study participants must have a diagnostic evaluation for cancer if the diagnosis of DM
was within 2 years prior to the Screening Visit

Exclusion Criteria:

- Has ongoing severe dysphagia (e.g., requires a feeding tube) for the 3 months prior to
Screening

- Has known hypersensitivity to any oligodeoxynucleotide

- Has a history of drug or alcohol abuse within one year of screening, or evidence of
drug abuse by urine drug screening

- Has body weight >140 kg

- Has a diagnosis of Juvenile DM, IBM, drug-induced toxic myopathy, metabolic myopathy,
dystrophy, cancer-associated DM, or connective tissue disease-associated DM (e.g.,
overlap syndrome)

- Has received one or more of following prohibited treatments within the interval noted
prior to Screening (Visit 1):

1. Rituximab within 24 weeks (Note: patients who received rituximab are only
eligible for inclusion if B-cell counts are confirmed to be within normal limits)

2. Intravenous corticosteroids within 12 weeks

3. Antimalarials (e.g., hydroxychloroquine) within 36 weeks

4. Topical corticosteroids (excluding scalp) within 2 weeks

- Has evidence of or has required treatment for cancer (except for treated, non-invasive
carcinoma of the skin or cured cervical carcinoma-in-situ) within 5 years

- Has interstitial lung disease requiring the use of supplemental oxygen