Inclusion Criteria:

   1. Male or female children and adolescents aged ≥6 years and ≤16 years

   2. Diagnosis of Congenital DM1 (also known as Steinert's disease)

      - Diagnosis must be genetically confirmed

      - One or more of the following clinically relevant (e.g. requiring medical
      intervention) signs or symptoms was evident within the first month after birth:

         - Hypotonia

         - Generalized weakness

         - Respiratory insufficiency

         - Feeding difficulties

         - Clubfoot or another musculoskeletal deformity

   3. Subject must be able to walk and complete the 10-meter walk-run test
   (orthotics/splints allowed, forearm crutches are not allowed)

   4. Written, voluntary informed consent must be obtained before any study related
   procedures are conducted.

      - Where a parent or LAR provides consent, there must also be assent from the
      subject

   5. Subject's caregiver must be willing and able to support participation for duration of
   study

   6. Subject must be willing and able to comply with the required food intake restrictions
   as outlined per protocol

Exclusion Criteria:

   1. Not able to walk; (full time wheel chair use)

   2. Body mass index (BMI) less than 13.5 kg/m² or greater than 40 kg/m²

   3. New or change in medications/therapies within 4 weeks prior to Screening

   4. Use of strong CYP3A4 inhibitors (e.g clarithromycin, telithromycin, ketoconazole,
   itraconazole, posaconazole, nefazodone, idinavir and ritonavir) within 4 weeks prior
   to Baseline

   5. Concurrent use of drugs metabolized by CYP3A4 with a narrow therapeutic window (e.g.
   warfarin and digitoxin)

   6. Current enrollment in a clinical trial of an investigational drug or enrollment in a
   clinical trial of an investigational drug in the last 6 months

   7. Existing or historical medical conditions or complications (e.g. neurological,
   cardiovascular, renal, hepatic, endocrine, gastrointestinal or respiratory disease)
   which would cause the investigator to conclude that the subject will not be able to
   perform the study procedures or assessments or would confound interpretation of data
   obtained during assessment

   8. Hypersensitivity to tideglusib and its excipients including allergy to strawberry