Oral molecule derived from a natural fragment of the growth factor IGF-1. Being investigated in rare neurodevelopmental disorders such as Phelan-McDermid syndrome.
Regulatory status
In clinical trials
Family
Synthetic analog of cyclo-glycine-proline (diketopiperazine derived from IGF-1)
Scientific evidence
Low
Number of findings
1
Where it acts
Brain and sleep
Also known as
NNZ-2591, NNZ 2591
Regulatory status
FDA (US): Not approved (in a phase 3 trial in Phelan-McDermid syndrome since 2026; Fast Track designation).
EMA (EU): Not approved.
Dose
There is no established dose in humans. In the phase 2 trial in children with Phelan-McDermid syndrome it was given orally twice a day, increasing from 4 to 12 mg/kg over 6 weeks (Neurol Genet 2025).
Safety
In the phase 2 trial, adverse effects were mostly mild or moderate; 3 of 18 children dropped out because of adverse effects considered unrelated (COVID-19, an epileptic seizure). Very limited data. Use only in clinical trials or research, under medical supervision; buying it is not recommended.
Effect by goal · level of evidence
Symptoms of Phelan-McDermid syndrome in children
improvesLowclinical trial (A)in people
16/18 improve
Open-label phase 2 trial with no control group in 18 children aged 3 to 12 years over 13 weeks: physicians rated improvement in 16 of 18 and caregivers in 15 of 18, with changes in behavior, sleep, digestive symptoms, and communication. Because there was no placebo, the result needs to be confirmed.
Based on cyclic glycine-proline, a small compound formed when IGF-1 is broken down, which regulates the amount of IGF-1 available in the brain. The idea is to improve communication between neurons (synapses) in disorders where it is impaired. In animals it showed protective effects after brain injuries.
What the evidence says
In people
Symptoms of Phelan-McDermid syndrome in children. Open-label phase 2 trial, with no control group, in 18 children aged 3 to 12 years over 13 weeks: physicians rated improvement in 16 of 18 and caregivers in 15 of 18, with changes in behavior, sleep, digestive symptoms, and communication. Because there was no placebo, the result needs to be confirmed. PubMed 41450730