MBX
Live News • Jun 14
MBX Biosciences Shares Fall Despite Encouraging One-Year Canvuparatide Study Results MBX Biosciences reported one-year data from an open-label extension study of once-weekly canvuparatide in chronic hypoparathyroidism, with 57% of patients meeting responder criteria.
The extension data pointed to sustained clinical benefits, including measures related to calcium balance, kidney function and bone remodeling, and a 90% patient retention rate.
The company said its Phase 3 pivotal trial for canvuparatide remains on track to start, while the stock fell 19.6% in premarket trading following the update.
The key takeaway is that the clinical package around canvuparatide is building. However, the sharp share reaction shows the market may have had different expectations or concerns about trial design, timelines or perceived commercial potential.
For those following MBX, the central risk remains clinical and regulatory execution around the Phase 3 program, since future value for the stock is likely to hinge on how that pivotal study is designed, enrolled and ultimately read out. Announcement • Jun 13
MBX Biosciences Announces One-Year Data Demonstrating Sustained Benefit Of Once-Weekly Canvuparatide As A Potential PTH Replacement Therapy In Chronic Hypoparathyroidism MBX Biosciences announced full results from the 12-week Avail Phase 2 trial and new one-year data from the ongoing open-label extension (OLE) study of once-weekly canvuparatide in adult patients with chronic hypoparathyroidism. Responder rate of 57% at one year in open-label extension (OLE) was comparable to 63% at 12 weeks in Phase 2 Avail trial. Results were consistent with restoration of systemic PTH activity through serum calcium normalization, reduction of urine calcium excretion, restoration of bone metabolism and increase of eGFR (a measure of kidney function). High retention rate with 90% of patients entering the OLE remaining in the study at one year. Canvuparatide was generally well tolerated with no new safety signals during the OLE. PK supports once-weekly dosing, with low peak-to-trough ratio and stable exposure. Phase 3 pivotal trial remains on track to initiate in Third Quarter 2026. Key findings from the 12-Week Avail Phase 2 Trial and One-Year OLE include: At 12 Weeks, 63% of canvuparatide-treated patients (30/48) achieved the primary composite endpoint compared with 31% of placebo-treated patients (5/16) (p=0.042). The primary endpoint was defined as maintaining albumin-adjusted serum calcium levels in the normal range and independence from conventional therapy (active vitamin D and >600 mg/day of calcium supplements). At One Year, 57% of evaluable patients (31/54) achieved responder status; zero contribution from rescue therapy (PRN) in the last week of the one-year treatment period. PK data from the Phase 2 trial continued to support the potential for once-weekly dosing. PK demonstrated consistent concentration of canvuparatide active drug with a Tmax of 2-3 days, minimal fluctuation and a peak-to-trough ratio of approximately 1.3 over a week, ensuring consistent systemic drug exposure over the entire weekly dosing interval. Mean serum calcium levels were maintained within the normal range through one year of treatment, while mean 24-hour urine calcium levels decreased from baseline and remained within the normal range, with continued reductions observed over time in both canvuparatide-treated patients and those who switched from placebo. Mean estimated glomerular filtration rate (eGFR) increased from baseline at Week 12 in canvuparatide-treated patients and remained improved through one year of treatment. Markers of bone resorption (C-terminal peptide; CTx) and formation (procollagen type 1 N-terminal propeptide; P1NP) demonstrated the expected pattern of bone turnover associated with PTH replacement therapy through one year. Changes in bone mineral density (BMD) T-scores and Z-scores were consistent with restoration of physiologic bone remodeling. Once-weekly canvuparatide was generally well tolerated through one year of treatment, with no new safety signals observed during the OLE. Most treatment emergent adverse events were mild or moderate in severity. No treatment-related serious adverse events were reported. Injection site reactions were reported in 10% of patients in the OLE. Trends toward improvement were observed across multiple SF-36v2 domains; however, interpretation was limited by incomplete baseline data. One-year OLE data from the Phase 2 trial will be presented at the 3rd Parathyroid Summit during ENDO 2026 on June 12, 2026, and full results from the 12-week Avail Phase 2 trial will be presented at ENDO 2026 at 3:00 pm CT on June 13, 2026, in Chicago. The Avail Phase 2 trial (NCT06465108) is a multicenter, randomized, double-blind, placebo-controlled study to evaluate the safety, pharmacokinetics, and efficacy of canvuparatide in patients with hypoparathyroidism. The study randomized 64 patients into four treatment arms: canvuparatide 400ug, 600ug, 800ug administered by subcutaneous once-weekly injection, and a placebo arm. The 12-week treatment period includes a four-week fixed dose period followed by an 8-week titration period during which canvuparatide dosing may be adjusted every two weeks in 200ug increments. The primary endpoint for efficacy is normalization of albumin adjusted serum calcium while independent from active vitamin D and calcium supplements. 
