Pivotal Phase 3 Study on Primary Hyperoxaluria Has High Quality Results

As seen in PR Newswire, researchers at the biopharmaceutical company OxThera AB have spent 52 weeks studying 25 patients with primary hyperoxaluria (PH), a rare disease that progressively damages the kidneys.

They wanted to see if their oral solution, Oxabact, could lower the plasma oxalate concentration in patients, stabilizing their kidneys. Their pivotal phase 3 trial’s completion yielded encouraging results.

Primary Hyperoxaluria

Primary hyperoxaluria (PH) is a rare genetic disorder that causes kidney damage due to the buildup of oxalate. Oxalate usually gets filtered by the kidneys, exiting the system in urine. However, a buildup of the compound causes kidney and bladder stones, stunted growth, kidney damage, and renal failure. There are drugs to minimize the calcification, and certain dietary changes and therapies can help control symptoms. More severe experiences may be treated with dialysis or organ transplants.

The Study

The researchers wanted to assess the safety and efficacy of the bi-modal enteric biotherapy Oxabact, an orally administered capsule that promotes oxalate’s secretion from the plasma to gut.
The study included patients with both variations of PH. During the screening they had a plasma oxalate concentration (Pox) of 10 μmol/L or more and an eGFR less than 90 ml/min/1.73 m2.
13 participants were treated with Oxabact while the remaining 12 received the placebo. 25 of the patients had PH type 1, while one patient had the rare PH type 2. The patients ranged in age from five to 54, with a mean age of 15 and a half years of age. The two groups preliminarily had about equal mean plasma oxalate levels, 14.8 µmol/L in Oxabact and 14.4 µmol/L in placebo, which the researchers hope to lower.
At 24 weeks, less than halfway into the trials, the researchers found the medication achieving their primary objective: to cause the study group to have a lower mean plasma oxalate concentration. By the end of the year-long study, 32 weeks later, the group receiving Oxabact demonstrated an almost complete turnaround, with stables levels of plasma oxalate. The placebo group experienced an increased concentration. By the study’s end, the groups had a mean difference of  – 3.8 (2.0) μmol/L (95% CI -7.8 – 0.2).
The group receiving Oxabact also showed improvements by other measurements in an overall comparison, including between comparable subgroups.  These measures included kidney function measured by estimated glomerular filtration rate and the number of kidney stones developed during the study.
Still, they have more work to do before the medicine reaches the market. The team believes their results are promising, and now they need to take steps to observe its long-term effects.
“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.
Oxthera’s Chief Operating Officer, Elisabeth Lindner said.
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.”

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