Clementia Pharmaceuticals has commenced a Phase II trial evaluating the safety and efficacy of palovarotene for the treatment of paediatric patients with multiple osteochondromas (MO), also called multiple hereditary exostoses (MHE).

The new MO-Ped trial expects to enrol 240 patients between the ages of two and 14 years at around 29 centres in 12 countries.

As part of the trial, patients will be randomised into one of three arms to receive a daily dose of weight adjusted equivalent of 2.5mg or 5mg of palovarotene, or placebo.

The trial’s primary efficacy endpoint is the rate of new osteochondromas (OCs) in the two treatment groups, as measured by whole body MRI, versus the placebo control group.

"MO is a rare, disabling disease, for which there are no approved treatments other than surgery."

Its secondary endpoints comprise the change in the total volume of OCs, the rate of new or worsening deformities and the rate of MO-related surgeries.

Exploratory endpoints of the trial include the rate of new or worsening functional limitations, quality of life and pain.

In addition, the trial’s safety evaluations feature adverse events, assessments of growth, bone mineral density, clinical laboratory tests and vital signs.

The MO-Ped trial is expected to treat the patients for 24 months and plans to release the interim analysis once the patients complete their 12-month MRI scans.

The 12-month long interim data readout of the trial is expected to take place in the first half of 2020, while the 24-month top-line results are scheduled to be available by the first half of 2021.

In a joint statement, MO-Ped Trialco-principal investigators Dror Paley and David Feldman said: “MO is a rare, disabling disease, for which there are no approved treatments other than surgery.

“MO causes benign tumours called osteochondromas to form on bones throughout the body, resulting in pain, deformity, limb length discrepancy, disability and eventually, arthritis and possible malignancy.”

Palovarotene, aRARγ agonist, is also being developed in a pivotal trial to treat patients with fibrodysplasia ossificans progressiva (FOP) and other diseases.