Open-label, Long-term, Extension Treatment Using Intra-Erythrocyte Dexamethasone Sodium Phosphate in Patients With Ataxia Telangiectasia Who Participated in the IEDAT-02-2015 Study

This is an international (North America, Europe, Africa, Asia and Australia), multi-center,
prospective, open-label treatment study, designed to continue to provide the study medication
to all patients who completed 12 months of treatment (including those treated with placebo)
in the IEDAT-02-2015 trial, completed the study assessments, do not present safety
contraindication to continuation of treatment, and provided informed consent. The study aims
to collect information on the long-term safety and efficacy of the trial treatment. Patients
meeting all selection criteria will receive monthly infusions of EDS-EP (dose range of ~14-22
mg DSP/infusion). If this dose of EDS-EP is not tolerated, the patient should be discontinued
from the study. During the study, long-term efficacy assessments will be performed every 6
months, while safety parameters will be assessed at each monthly visit.

The ICARS, EQ-5D-5L and the CGI-C/S will be administered by a site rater. All patients
enrolled in this study will have participated in Study IEDAT-02-2015, and there will be no de
novo enrollment of new patients.

The Principal Investigator will ask all patients who meet the above requirements, and
determine their interest in continuing to receive treatment with the study medication in a
new protocol. The Principal Investigator will then determine the eligibility of the patients
on the basis of his/her clinical judgement of patients' status and their safety.

Inclusion Criteria:

- Patient completed the double-blind period in the IEDAT-02-2015 trial and must have
completed the final (Visit 15/Month 12) efficacy assessments of IEDAT-02-2015.

- Patient tolerated the study medication, without any evidence of steroid adverse
events, or treatment-related severe/ serious adverse events

- Body weight > 15 kg.

- The patient and his/her parent/caregiver (if below the age of consent), or a legal
representative, has provided written informed consent to participate. If consent is
provided solely by the caregiver in accordance with local regulations, the patient
must provide assent to participate in the study

- Patient does not present safety contraindication for continuation of treatment, as
determined by the Principal Investigator (PI) according to the procedures described
below.

Procedure for selecting patients for further treatment in IEDAT-03-2018:

The Principal Investigator will ask all patients who meet the above requirements, and
determine their interest in continuing to receive treatment with the study medication in a
new protocol. The Principal Investigator will then determine the eligibility of the
patients on the basis of his/her clinical judgement of patients' status and their safety.

Exclusion Criteria:

General

1. Females that are

1. pregnant, or are breast-feeding (for EU countries only);

2. of childbearing potential, pregnant, or are breast-feeding (for US and Rest of
World countries).

Females of childbearing potential using adequate birth control, as determined by their
Health Care Provider, will be eligible.

2. A disability that may prevent the patient from completing all study requirements.

3. Current participation in a clinical study with another investigational drug.

Medical History and Current Status

4. CD4+ lymphocytes count <400/mm3 (for patients 6 years of age) or <200/mm3 (for
patients >6 years).

5. Current neoplastic disease.

6. Severe impairment of the immunological system.

7. Severe or unstable pulmonary disease.

8. Uncontrolled diabetes. Patients with diabetes that has been stabilized (i.e. no
hypoglycemic or hyperglycemic episodes in the past 3 months) will be eligible.

9. Any other severe, unstable, or serious disease or condition that in the Investigator's
opinion would put the patient at risk for imminent lifethreatening morbidity, need for
hospitalization, or mortality.

10. Eligibility of patients with abnormal laboratory test values will be determined by the
Investigator.

11. Confirmed hemoglobinopathies, e.g. hemoglobin C disease, sickle cell anemia, or
thalassemia.

12. Moderate or severe renal and/or hepatic impairment.

13. Patients who experienced moderate/ severe steroid side effects, or moderate/ severe
adverse events associated with the study medication administered in the IEDAT-02
study.

Prior/Concomitant Medication

14. Requires treatment with an oral or parenteral steroid. Treatment with inhaled or
intranasal steroids for asthma or allergies, as well as use of topical steroids will
be permitted.

15. Requires any other concomitant medication prohibited by the protocol.

16. Use of any drug that is a strong inducer/inhibitor of CYP3A4.