Study of the Selective GlyT1 Inhibitor Bitopertin for Steroid-Refractory Diamond-Blackfan Anemia

Dose Escalation: Monthly (every 4 weeks) up to a maximum dose of 60 mg bitopertin (5 mg, 10mg, 20mg, 40mg, 60mg). At each monthly (4 week) interval, a complete blood count (CBC) with differential and a reticulocyte analysis (including reticulocyte hemoglobin) will be collected prior to taking the higher dose. If the absolute reticulocyte count (ARC) is 60,000 /microL or higher, the subject will hold at the current dose level (or return to that level if escalation has already occurred) for an additional 4 weeks. If, after 8 weeks at that dose, response criteria are met this will be considered the minimum effective dose (MED) and shall be the treatment dose throughout the remainder of the study unless modifications are indicated.