MBX Biosciences, Inc. filed a current report on August 27, 2026 disclosing that the first patient had been dosed in its pivotal Phase 3 oPTimize clinical trial evaluating once-weekly canvuparatide for the treatment of chronic hypoparathyroidism.

Key Highlights

  • Trial milestone: First patient dosed in the pivotal Phase 3 oPTimize trial of canvuparatide in adults with chronic hypoparathyroidism on August 27, 2026.
  • Trial design: Global, multicenter, randomized, double-blind, placebo-controlled study with approximately 160 patients enrolled 3:1 (canvuparatide to placebo) during a 26-week double-blind period.
  • Dosing schedule: Canvuparatide will be administered once weekly, beginning at 600 micrograms and titrated up to 1,600 micrograms, using the device intended for commercial use.
  • Primary endpoint: Proportion of patients achieving a composite responder endpoint at Week 26, including normal albumin-adjusted serum calcium, independence from active vitamin D, and calcium supplementation reduced to 600 milligrams per day or less.
  • Extension period: A 78-week open-label extension follows the 26-week double-blind treatment period.
  • Emerging growth company: MBX Biosciences, Inc. is designated an emerging growth company under applicable SEC rules, as indicated on the filing cover.

MBX Biosciences Advances Canvuparatide into Pivotal Phase 3 Testing for Chronic Hypoparathyroidism

MBX Biosciences, Inc. (NASDAQ:MBX), a biopharmaceutical company focused on endocrine and metabolic disorders and headquartered in Carmel, Indiana, announced through its August 27, 2026 filing that the Phase 3 oPTimize trial has begun enrolling patients. According to the filing, the study is structured as a global, multicenter, randomized, double-blind, placebo-controlled trial, with approximately 160 adult patients to be randomized in a 3:1 ratio receiving canvuparatide or placebo across a 26-week double-blind treatment period.

The 26-week double-blind period, as described in the filing, is divided into three stages: a four-week fixed-dose period at 600 micrograms once weekly, an 18-week individualized dose-titration period allowing doses up to 1,600 micrograms once weekly, and a four-week dose-maintenance period through Week 26 without increases in study drug, active vitamin D, or calcium supplementation. The composite primary endpoint at Week 26 requires patients to simultaneously maintain normal albumin-adjusted serum calcium, achieve independence from active vitamin D, reduce calcium supplementation to 600 milligrams per day or less, and avoid any increase in study drug dose during the four weeks preceding the assessment.

Key secondary endpoints cited in the filing include normalization of urinary calcium excretion while maintaining normal serum calcium in patients with elevated baseline urinary calcium excretion, and improvement of physical functioning and hypocalcemia-related symptoms. The trial will also assess bone mineral metabolism, kidney health, bone biomarkers, and patient-reported outcomes. The filing contains forward-looking statements, which the company states are subject to risks including regulatory approval uncertainties, clinical trial execution risks, and reliance on third parties, among others described in MBX Biosciences' previously filed Annual Report on Form 10-K for the year ended December 31, 2025 and subsequent regulatory filings.

What Was Disclosed

MBX Biosciences reported the dosing of the first patient in its Phase 3 oPTimize trial of once-weekly canvuparatide for chronic hypoparathyroidism, providing the full trial design, primary and secondary endpoints, and dosing parameters in an 8-K current report dated August 27, 2026.