11 June 2021
OxThera reports results from Phase 3 ePHex study with Oxabact in primary hyperoxaluria patients with maintained kidney function
STOCKHOLM, June 11, 2021 /PRNewswire/ — OxThera AB, a privately-held biopharmaceutical company dedicated to improving the lives of people with Primary Hyperoxaluria (PH), announces completion of its pivotal Phase 3 study and reports top line results.
OxThera’s 52-week OC5-DB-02 study “A Phase III Double-Blind, Randomised Study to Evaluate the Long-Term Efficacy and Safety of Oxabact® in Patients with Primary Hyperoxaluria” (ePHex) enrolled patients with all types of PH, who had to have a plasma oxalate (Pox) concentration ≥ 10 μmol/L and an eGFR < 90 ml/min/1.73 m2 during screening to be eligible for inclusion into the study.
Twenty-five patients were enrolled and randomly assigned 1:1 to either Oxabact (13) or placebo (12). Almost all patients (24) had been diagnosed with PH type 1, only 1 patient with PH type 2. The mean age at baseline for all subjects was 15.5. years (range 5 to 54 years), patients in the Oxabact arm were slightly younger. Baseline mean plasma oxalate in the two treatment arms was well balanced, 14.8 µmol/L in Oxabact and 14.4 µmol/L in placebo. Urinary oxalate excretion was slightly higher in the Oxabact group vs placebo; 2.10 and 1.76 mmol/day/1.73 m2, respectively.
The mean Pox concentration, the primary endpoint of the study, separated after week 24 in favor of Oxabact. The estimate of mean (SE) difference between treatment arms reached – 3.8 (2.0) μmol/L (95% CI -7.8 – 0.2) at week 52 (p=0.06), where the Oxabact group was essentially stable, and placebo increased. A trend in favor of Oxabact was observed for the overall comparison, and this was consistent across most pre-defined sub-groups. A supportive slope model demonstrated a similar magnitude of change (SE) of -6.1 (3.0) µmol/L (p=0.04).
Adverse events were well balanced between the 2 treatment arms, there were slightly more severe adverse events observed in the placebo arm than in the Oxabact arm.
“We are encouraged that the observed treatment effect towards the end of the study supports our hypothesis behind the mechanism of action of Oxabact, but of course disappointed that it did not reach statistical significance” said Elisabeth Lindner, Chief Operating Officer of OxThera. “Oxabact is an oral formulation of the bacterium Oxalobacter formigenes metabolizing oxalate that enters the GI tract through active and passive secretion from plasma. The hypothesis is that treatment with Oxabact could stop or delay disease progression. It appears that the study was not long enough to detect a difference in clinical endpoints, and OxThera is now seeking a partner to further develop Oxabact.”
Key secondary endpoints of the study, kidney function (estimated glomerular filtration rate, eGFR) and the number of adjudicated kidney stone events during the study, did not show a significant difference between treatment groups. During the 3 years pre-dose, 9 patients in the Oxabact arm reported in total 18 or more stone events, and 7 patients in placebo reported in total 16 or more stone events. On study, 7 stone events occurred in 13 Oxabact patients and 8 stone events in 12 placebo patients.
“As a physician treating patients with PH, it is of primary importance to me that my patients are stable.” said Dr. Gema Ariceta, Principal Investigator at Val d’Hebron hospital, Barcelona, Spain, and highest recruiter of patients in the ePHex study. Six out of 8 enrolled patients at her study site were randomized to Oxabact during the study. “Even if I am disappointed that the study did not meet significance, I think it is important to look at individual patients in such a rare disease and to see if treatment effects can be seen. The safety profile of Oxabact, as well as oral administration, would make it a good background treatment candidate for patients.”
The study results have been accepted for oral presentation at the upcoming European Society of Pediatric Nephrology meeting, 16-19. September 2021, Amsterdam, and will be presented by Dr. Ariceta on Saturday, 18. September, in Session 16 (Hall 2) between 16:45 – 18:30.
Oxabact is a bi-modal enteric biotherapy containing a lyophilized formulation of Oxalobacter formigenes, a non-pathogenic, oxalate-degrading commensal bacterium. Oxabact is administered orally as a coated capsule. By promoting active and passive secretion of oxalate from the plasma into the gut, Oxabact is able to increase excretion of oxalate. Oxabact is a registered trademark of OxThera Intellectual Property AB.
OxThera AB is a Swedish biopharmaceutical company developing a new treatment for primary hyperoxaluria (PH) – a rare genetic and devastating disease with fatal outcomes.