A Study to Understand How Nerandomilast Works in People With Active Idiopathic Inflammatory Myopathies

Open to people ages 18 years and up

1. Male or female adult individuals from ≥18 years of age (or alternative age for adults based on local regulations) on the date of signing the informed consent.
2. A definite or probable clinical diagnosis of idiopathic inflammatory myopathy (IIM) according to the 2017 American college of rheumatology (ACR)/European alliance of associations of rheumatology (EULAR) classification criteria.
3. Participants with overlap myositis (OM) must have IIM as the predominant disease.
4. Participants ≥18 years of age (or alternative age for adults based on local regulations) with juvenile dermatomyositis (JDM) can only be included if they were 15 years old or older at first onset of DM symptoms.

5. For participants diagnosed with DM

   Disease activity defined by moderate to severe myopathy with manual muscle testing-8 (MMT-8) of ≥80 and ≤142/150 and cutaneous dermatomyositis disease area and severity index activity score (CDASI-A) ≥6 at screening and baseline and at least 2 of the following core set measures (CSM) abnormalities at screening:

   • Patient global assessment (PtGA) ≥2 cm
   • Physician global activity (PhGA) derived from myositis disease activity assessment tool (MDAAT) ≥2 cm
   • Extramuscular disease activity as per MDAAT ≥2 cm
   • At least 1 muscle enzyme (aldolase, creatine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT), or lactate dehydrogenase (LDH)) ≥1.5× upper limit of normal (ULN),
   • Health assessment questionnaire-disability index (HAQ-DI) ≥0.25.

6. For participants diagnosed with anti-synthetase syndrome (ASyS)* and OM*:

   1. Active disease based on at least 1 of the following criteria:
      • CK ≥4× ULN at screening
      • Muscle biopsy indicative of active IIM within up to 6 months prior to screening
      • Evidence of active myositis by electromyography (EMG) within up to 6 months prior to screening
      • Magnetic resonance imaging with evidence of active myositis within up to 6 months prior to screening AND
   2. Minimum disease activity defined by moderate to severe myopathy with MMT-8 of ≥ 80 and ≤142/150 at screening and baseline and at least 2 of the following CSM abnormalities at screening:
      • PtGA ≥2 cm
      • PhGA derived from MDAAT ≥2 cm
      • Extramuscular disease activity as per MDAAT ≥2 cm
      • At least 1 muscle enzyme ≥1.5× ULN
      • HAQ-DI ≥0.25. * Note: Inclusion Criteria #6a and #6b must be reviewed by the central eligibility committee.
7. The participant must be on background therapy for IIM. The standard treatments that are allowed as background therapy for IIM include:
   1. Oral corticosteroid (OCS) monotherapy in doses ≤20 mg prednisone (or prednisone equivalent), OR
   2. One of the following immunosuppressants/immunomodulators: azathioprine, mycophenolate mofetil or mycophenolic acid, methotrexate, 6 mercaptopurine, sulfasalazine, leflunomide, mizoribine, cyclosporine, tacrolimus in doses as per local guidelines (combinations of these treatments are not allowed), OR
   3. One of the following antimalarials: hydroxychloroquine quinacrine, chloroquine, OR
   4. Any combination of OCS in doses ≤20 mg prednisone (or prednisone equivalent), 1 of the above immunosuppressants/immunomodulators, and/or 1 of the above antimalarials
      • If using OCS for IIM, the participant must be introduced ≥4 weeks prior to screening. the dose must be stable and not exceed 20 mg/day of prednisone (or equivalent) 2 weeks prior to screening
      • If using immunosuppressants/immunomodulators and/or antimalarials the participant must have been on the same medication for ≥12 weeks before randomisation and on a stable dose for ≥4 weeks prior to randomisation
8. Woman (or women) of childbearing potential (WOCBP) must be ready and able to use highly effective methods of birth control for a period of 28 days before treatment initiation, throughout the trial, and for a period of at least 5 days after the last dose of investigational medicinal product (IMP). WOCBP taking oral contraceptives also have to use one barrier method.
9. Signed and dated written informed consent in accordance with ICH-GCP and local legislation prior to admission to the trial.

1. Major surgery (major according to the investigator's assessment, e.g. hip replacement) performed within 6 weeks prior to randomisation or planned during the trial period.
2. Any documented active or suspected malignancy or history of malignancy within 5 years prior to screening, except appropriately treated basal cell carcinoma of the skin, or in situ squamous cell carcinoma of the skin, or in situ carcinoma of uterine cervix.
3. Participants who must or wish to continue the intake of restricted medications or any drug considered likely to interfere with the safe conduct of the trial.
4. Participants with uncontrolled IIM manifestations that, in the opinion of the investigator, would be likely to require treatment with restricted medications (e.g. cyclophosphamide) during the trial.
5. Participants diagnosed with advanced interstitial lung disease (ILD), with:
   1. Forced vital capacity (FVC) <70% of predicted at screening OR
   2. A history of any of the following up to 12 months prior to screening:
      • Diffusing capacity of the lung for carbon monoxide (DLCO) <70% of predicted
      • Hypoxemia requiring supplemental oxygen therapy, not attributable to sleep apnoea OR
      • Recent ILD exacerbation or respiratory hospitalisation related to ILD within the last 3 months.
6. Participants with Immune-mediated necrotizing myositis (IMNM); Inclusion body myositis (IBM), cancer-associated polymyositis (PM) or DM, and non-inflammatory myopathies (e.g. muscular dystrophies), antibody-negative PM, or amyopathic dermatomyositis (ADM) with a CDASI-A score ≤14.
7. Participants who experience improvement in MMT-8 (>10%) or PhGA (≥2 cm) from screening (Visit 1) to randomisation (Visit 2).
8. Severe muscle damage defined as a global muscle damage score of >5 on a 10-centimetre visual analogue scale (VAS) scale on the myositis damage Index (MDI).
9. Further exclusion criteria apply.