An Open-Label Extension Study of BPN14770 in Subjects With Fragile X Syndrome

Open to males ages 9-45

1. Subject has completed the Week 13 visit, whether on treatment or discontinued from treatment, from one of two parent clinical trials with

   BPN14770:

   1. Study 204
   2. Study 301 Subjects who discontinued study treatment early due to AEs deemed related to study treatment by the investigator in one of the parent studies will NOT be eligible, regardless of whether the Week 13 visit was completed.
2. Subjects with a history of seizure disorder who are currently receiving treatment with antiepileptics must have remained seizure-free during the parent study. Any subject experiencing a seizure during the parent study is not eligible to continue into this long-term safety study.
3. Subject must be willing to practice barrier methods of contraception while on study, if sexually active. Abstinence is also considered a reasonable form of birth control in this study population.
4. Subject has a parent, legal authorized guardian, or consistent caregiver.
5. Subject and caregiver are able to attend the clinic regularly and reliably.
6. If subject is his own legal guardian, he is able to understand and sign an informed consent form to participate in the study.
7. For subjects who are not their own legal guardian, subject's parent/legally authorized guardian is able to understand and sign an informed consent form for their child to participate in the study.
8. If subject is not his own legal guardian, subject must provide assent for participation in the study if he has the cognitive ability to do so.

• 1. History of, or current cardiovascular, renal, hepatic, respiratory, gastrointestinal, psychiatric, neurologic, cerebrovascular, or other systemic disease that would place the subject at risk or potentially interfere with the interpretation of the safety, tolerability, or efficacy of the study treatment. Common conditions such as mild hypertension, etc. are allowed per the principal investigator's (PI) judgement as long as they are stable and controlled by medical therapy that is constant for at least 4 weeks before randomization.
  2. Renal impairment, defined as serum creatinine >1.25×ULN per the latest available laboratory results from the parent study.
  3. Cirrhosis, unstable chronic liver disease or acute liver disease. Hepatic impairment, defined as ALT or AST elevation > 2 × ULN per the latest available laboratory results from the parent study. Subjects with stable chronic hepatitis B on oral anti-viral therapy and subjects cured of chronic hepatitis C are allowed. Subjects with Gilbert syndrome are allowed.
  4. Clinically significant abnormalities, in the investigator's judgement, in safety laboratory tests, vital signs, or ECG, as measured at the final visit of the parent study.
  5. Substance abuse documented during the parent study.
  6. Significant hearing or visual impairment that may affect the subject's ability to complete the test procedures.
  7. Concurrent major psychiatric condition (eg, major depressive disorder, schizophrenia, or bipolar disorder) as confirmed by the investigator. Subjects with additional diagnosis of autism spectrum disorder or anxiety disorder will be allowed.
  8. Subject has active diseases that would interfere with participation, such as acquired immunodeficiency disorder, hepatitis C, hepatitis B, or tuberculosis.
  9. Subject has participated in another clinical trial within the 30 days preceding screening OTHER THAN one of the two studies required per Inclusion Criteria 1.