• Blood parameters [ Time Frame: At 6 months and throughout the study ] [ Designated as safety issue: Yes ]
• Vital signs [ Time Frame: At 6 months and throughout the study ] [ Designated as safety issue: Yes ]
• Questionnaires of life questionnaire [ Time Frame: At 6 months and throughout the study ] [ Designated as safety issue: Yes ]
• Pharmacoeconomic evaluation [ Time Frame: At 6 months and throughout the study ] [ Designated as safety issue: No ]

•  Clinical assessments of the fracture site
• Blood parameters
• Vital signs
• Questionnaires of Life
• Pharmacoeconomic evaluation

This is a randomised, controlled, open-label study of a single intralesional administration of I-040302 or a single bone marrow aspirate or a single steroid injection (methylprednisolone). Subjects will undergo screening with X-ray and magnetic resonance imaging (MRI) in the diagnosis of a solitary bone cyst.

• Drug: I-040302
• Other: Standard of Care

• Experimental: I-040302 doses of up to 1 mg, 2 mg or 4 mg of TGplPTH1-34
• Active Comparator: Standard of care (bone marrow aspirate or steroids)

Inclusion Criteria:

1. Subjects 6 - 16 years of age

2. Diagnostic evidence of unicameral bone cysts based on one or more of a combination of any of the following methods:

   • Cyst fluid examination
   • Plain radiographs
   • MRI

3. Subjects with the following types of cysts:

   • Intact cysts that are either growing or at risk of fracture, requiring surgical intervention
   • Persistence of a cyst cavity following cyst fracture that has received conservative treatment/s to repair the fracture
   • Persistence of a cyst cavity despite repeated interventions
4. Subjects with bone cyst volumes < 30 mL
5. Subjects must be appropriately communicative to verbalise pain.
6. Subjects must be able to understand and be willing to comply with the protocol procedures.
7. Subjects who have provided written informed consent to participate in the study
8. The legally authorised representative of the child must give written informed consent after the child has agreed to participate in the study.

Exclusion Criteria:

1. A history of/or presence of active cancer
2. Family history of retinoblastoma
3. Indication of aneurysmal bone cyst on MRI, cyst aspiration or histology
4. Possible presence of osteosarcoma or uncertain histology
5. Systemic or localised infection at time of surgery
6. Evidence of immune-suppression
7. Evidence of hypercalcemia
8. Cyst volume > 30 mL
9. Fracture present in the cortical bone surrounding the cyst
10. Evidence of rapid venous drainage from the cyst determined by rapid disappearance of X-ray contrast medium during the surgical process.
11. Suspected or known evidence of allergic reactions towards any of the components of I-040302
12. Known clinically significant organ or systemic diseases such that, in the opinion of the investigator, the significance of the disease will compromise the subject's participation in the study
13. Pregnant or lactating females
14. Participation in another clinical trial within 3 months prior to trial start