The trial was discontinued by the Sponsor

This study will evaluate the safety and tolerability of RTX-134 in adult patients with PKU.

This is a Phase 1b first-in-human trial in adult subjects with PKU. The primary objective of this study is to evaluate the safety and tolerability of RTX-134 following intravenous administration of a single dose. RTX-134 consists of allogeneic human red cells expressing the AvPAL (Anabaena variabilis phenylalanine ammonia lyase) gene inside the cell. The trial is designed to determine a preliminary dose and inform a dosing schedule that is deemed safe, tolerable, and potentially effective. Four dose levels are planned, additional dose levels may be explored. Following administration, subjects will be monitored until 28 days after last detection of RTX-134. Detection of RTX-134 will be evaluated using multiple pharmacokinetic (PK) and pharmacodynamic (PD) assessments including measurement of trans-cinnamic acid (tCA).

Inclusion Criteria

1. Age 18 years or older with:

   1. A clinical diagnosis of PKU, and
   2. Average blood phenylalanine level ≥ 600 µmol/L based on 2 assessments up to 3 weeks apart during the 6-month period before Day 0 (per available data)

2. Stable diet, including medical formula

3. Must be a man or a woman not of childbearing potential and agree to use adequate contraception throughout and for one year following study participation.

4. Adequate organ function

5. Negative antibody detection on type and screen and no evidence of clinical hemolysis

Exclusion Criteria

1. Known hypersensitivity to any component of study treatment
2. Prior treatment with Pegaliase
3. Start of sapropterin dihydrochloride within 3 weeks of study dosing
4. Use of an investigational agent within 28 days of study dosing
5. Concurrent participation in an interventional trial involving ongoing treatment, including placebo.
6. Infections requiring antimicrobial treatment within 7 days of study dosing
7. Chronic infections, such as HIV, hepatitis B, or untreated hepatitis C
8. Conditions that may alter survival of red blood cells, (e.g., autoimmune diseases, splenectomy, etc)
9. Pregnant or breastfeeding