Study to Evaluate the Efficacy and Safety of Oxabact (OC5) in Primary Hyperoxaluria Patients Who Are on Dialysis

Inclusion Criteria:

1. Signed informed consent (as applicable for the age of the subject). A separate
appendix to the informed consent will be signed by patients who will participate in
the sub-study.

2. Male or female subjects ≥ 2 years of age. Subjects have to be able to swallow size 4
capsules twice daily for 6 weeks, or use a gastric tube that allows for
administration of size 4 capsules.

3. A diagnosis of PH (as determined by standard diagnostic methods).

4. Patient should be on a stable dialysis regimen for at least two weeks before
baseline.

5. Pre-dialysis plasma oxalate ≥40 micromole/L.

6. Subjects receiving vitamin B6 must be receiving a stable dose for at least 3 months
prior to screening and must remain on the stable dose during the study. Subjects not
receiving vitamin B6 at study entry must be willing to refrain from initiating
vitamin B6 during study participation.

Exclusion Criteria:

7. Inability to swallow size 4 capsules twice daily for 6 weeks or using a gastric tube
not suited for administration of size 4 capsules via the tube.

8. Ongoing treatment with immunosuppressive medication.

9. The existence of secondary hyperoxaluria, e.g. hyperoxaluria due to bariatric surgery
or chronic gastrointestinal diseases such as cystic fibrosis, chronic inflammatory
bowel disease and short-bowel syndrome.

10. Use of antibiotics to which O. formigenes is sensitive (see section 7.2.2), including
current antibiotic use, or antibiotics use within 14 days of initiating study
medication.

11. Current treatment with a separate ascorbic acid preparation.

12. Pregnancy.

13. Women of childbearing potential who are not using adequate contraceptive precautions.
Sexually active females, unless surgically sterile or at least 2 years
post-menopausal, must be using a highly effective contraception (including oral,
transdermal, injectable, or implanted contraceptives, IUD, abstinence, use of a
condom by the sexual partner or sterile sexual partner) for 30 days prior to the
first dose of OC5 and must agree to continue using such precautions during the
clinical study.

14. Presence of a medical condition that the Principal Investigator considers likely to
make the subject susceptible to adverse effect of study treatment or unable to follow
study procedures.

15. Participation in any study of an investigational product, biologic, device, or other
agent within 30 days prior to the first dose of OC5 or not willing to forego other
forms of investigational treatment during this study.