MBX Biosciences said Monday that its experimental drug canvuparatide cleared the bar in a
Phase 2 trial
in a rare endocrine disorder called hypoparathyroidism.
The once-weekly drug helped 63% of patients (30 out of 48 participants) maintain a normal range of albumin-adjusted serum calcium levels while also staying off conventional therapy of active vitamin D and daily calcium supplements at week 12, the Indiana-based drug developer said.
At the same time point, 31% of patients on placebo (5 out of 16 people) achieved the composite primary endpoint. The study results were statistically significant at a p-value of 0.042.
Investors were anticipating strong results from MBX’s Phase 2 study, codenamed Avail. The company’s share price
$MBX
rose 36% in post-market trading on Friday night after MBX said it would present the topline data before Monday’s opening bell.
If Monday’s data are replicated in a larger Phase 3 trial, anticipated to begin next year, the biotech’s contender could potentially offer an alternative to an approved daily medicine marketed as Yorvipath by Ascendis Pharma. Other biopharmas also aim to treat the rare endocrine disorder, like Septerna and AstraZeneca, whose Amolyt-developed drug
succeeded in a Phase 3
in March.
Hypoparathyroidism impacts about 250,000 people in the US and Europe and can sometimes lead to chronic kidney disease. Takeda previously marketed a treatment for the rare endocrine condition, which is marked by reduced calcium levels and impairments to daily quality of life, but the Japanese pharma
took it off the market
due to manufacturing hurdles.
“Hypoparathyroidism poses a substantial burden to patients, who often face complex treatment regimens and unpredictable swings in calcium levels that can lead to serious complications,” Mishaela Rubin, study investigator and Columbia University professor, said in a press release. “The 12-week and 6-month data provide promising early evidence that this investigational therapy may offer a potential option for long-term management, pending further study.”
The study’s placebo-adjusted response rate of 32% came in below management expectations. In a note to clients last month, Mizuho analyst Uy Ear said MBX management anticipated a placebo-adjusted rate of 48%.
While the response rate ended up being higher in the treatment arm, at 63% versus a projection of 55%, the placebo performed much better than expected. MBX had anticipated a 7% placebo response rate. The end result was 31%.
In an interview with
Endpoints News
, CEO Kent Hawryluk said the placebo group was a “small sample size.”
“While the placebo response was higher than originally planned, it’s not unusual. If we looked at the once-daily injectable,” Hawryluk said, referring to Ascendis’ Yorvipath, “in their Phase 2, they had a 27% placebo response for their primary endpoint. Importantly, that reduced in their longer Phase 3 study.
“There’s a logical reason for that,” the MBX CEO continued. Hypoparathyroidism patients “can’t stay in the normal range of serum calcium for long without their conventional therapy,” he said.
MBX said canvuparatide, previously known as MBX 2109, was “generally well-tolerated.” No treatment-related discontinuations were reported in the Phase 2 trial.
The biotech also said 94% of patients elected to enroll in the open-label extension, with a 79% responder rate at six months.
“We hope [to] provide a best-in-class treatment option for patients, which gives them freedom from having to take a daily injection, which is a daily reminder of their disease,” Hawryluk said. “We believe that we’ve shown with these results that we offer continuous infusion-like PTH exposure, which brings back their natural physiology, which they’re lacking with their disease.”
Three doses were tested in the Phase 2. Chief medical officer Sam Azoulay told Endpoints that the biotech is still sifting through the full data package to determine the dose for the upcoming Phase 3.
The topline data marked the second clinical readout for MBX since the biotech
went public
.
The only other key clinical results since last year’s $163 million IPO were
Phase 1 data
for a different drug in treating post-bariatric hypoglycemia. That investigational medicine, called MBX 1416 or imapextide, is now in
Phase 2
.
Another drug, nicknamed MBX 4291, entered
Phase 1
for obesity earlier this month. The biotech hopes MBX 4291 could compete in the obesity drug market as a once-monthly GLP-1 and GIP co-agonist.
All of the drug candidates derive from the same platform at MBX, which aims to extend the half-life of peptide therapies.
Hawryluk said Monday’s results could have “readthrough” to those other pipeline drug candidates. With canvuparatide, he noted, MBX was able to take a hormone peptide with a natural half-life of about one hour and turn it into a once-weekly treatment candidate.