8-K: BridgeBio Encaleret Phase 3 Success in ADH1

BridgeBio Pharma, Inc. announced positive topline results from its Phase 3 CALIBRATE study of encaleret for Autosomal Dominant Hypocalcemia Type 1 (ADH1), meeting all primary and key secondary endpoints.

Summary

• BridgeBio Pharma reported positive topline results from its global Phase 3 CALIBRATE study of encaleret for Autosomal Dominant Hypocalcemia Type 1 (ADH1).
• The study met all pre-specified primary and key secondary efficacy endpoints.
• The primary endpoint showed 76% of encaleret-treated participants achieved both serum and urine calcium within target ranges at Week 24, compared to 4% on conventional therapy at Week 4 (p<0.0001).
• A key secondary analysis revealed 91% of encaleret participants achieved intact PTH above the lower limit of the reference range at Week 24, versus 7% on conventional therapy at Week 4 (p<0.0001).
• Encaleret was well-tolerated, with no discontinuations related to the study drug.
• The company plans to submit a New Drug Application (NDA) to the FDA in the first half of 2026 and a Marketing Authorization Application (MAA) to the EMA thereafter.
• BridgeBio also intends to initiate registrational studies for encaleret in pediatric ADH1 in Q1 2026 and in chronic hypoparathyroidism in 2026.

Sentiment

Score: 9

Explanation: The filing reports overwhelmingly positive Phase 3 clinical trial results for encaleret, meeting all primary and key secondary endpoints with high statistical significance and a favorable safety profile. This represents a major de-risking event for the drug and the company, indicating strong potential for regulatory approval and market success in a rare disease with unmet needs. The planned regulatory submissions and expansion into additional indications further bolster the positive outlook.

Positives

• Encaleret met all pre-specified primary and key secondary efficacy endpoints in the Phase 3 CALIBRATE study for ADH1.
• 76% of encaleret-treated participants achieved both serum and urine calcium within target ranges at Week 24, significantly higher than 4% on conventional therapy (p<0.0001).
• 91% of encaleret participants achieved intact PTH above the lower limit of the reference range at Week 24, compared to 7% on conventional therapy (p<0.0001).
• Encaleret was well-tolerated with no discontinuations related to the study drug.
• 97% of randomized participants elected to continue in the ongoing long-term extension study, indicating high patient satisfaction and perceived benefit.
• The drug demonstrated rapid action, with 71% of participants achieving serum calcium within the reference range by Day 3.
• By Week 20, 98% of encaleret recipients had serum calcium in the target range, significantly better than 33% of participants on conventional therapy.
• Encaleret achieved a mean increase in corrected calcium by 0.82 mg/dL and a mean reduction in 24-hour urine calcium by 200 mg/day from Week 4 to Week 24 (both p<0.0001).
• Encaleret has received Fast Track Designation by the U.S. FDA and Orphan Drug Designation in the U.S., European Union, and Japan.

Risks

• Initial and ongoing data from preclinical studies and clinical trials may not be indicative of final data.
• The potential size of target patient populations for product candidates may not be as large as anticipated.
• The design and success of ongoing and planned clinical trials are uncertain.
• Future regulatory filings, approvals, and/or sales are not guaranteed.
• Regulatory agencies (e.g., FDA) may not agree with regulatory approval strategies, components of filings, or sufficiency of data.
• The continuing success of collaborations is not assured.
• Ability to obtain additional funding, including through less dilutive sources of capital than equity financings, is a risk.
• Potential volatility in the company's share price.
• Impacts of current macroeconomic and geopolitical events, including hostilities in Ukraine, Israel, and Gaza Strip, increasing inflation, and changing interest rates, on business operations and expectations.

Future Outlook

BridgeBio Pharma plans to submit a New Drug Application (NDA) for encaleret to the FDA in the first half of 2026, followed by a Marketing Authorization Application (MAA) to the EMA thereafter. The company also intends to initiate registrational studies for encaleret in pediatric ADH1 in Q1 2026 and a Phase 3 study in adults with chronic hypoparathyroidism in 2026, aiming to expand the drug's potential applications.

Management Comments

• "The remarkable results of the landmark CALIBRATE study represent an important step forward for patients living with ADH1. Unlike conventional therapy with calcium supplements and active vitamin D, encaleret not only increased and maintained both blood calcium and endogenous parathyroid hormone (PTH) but also decreased and maintained urine calcium in the normal range. The consistent and clinically meaningful improvements in calcium and mineral homeostasis indicate its potential to become an important new standard of care for this patient community." Michael Mannstadt, M.D., Chief of the Endocrine Unit at the Massachusetts General Hospital.
• "BridgeBio's CALIBRATE Phase 3 results are promising and offer potential for a targeted therapy for people living with ADH1, including those yet to be diagnosed." Patty Keating, Executive Director of the HypoPARAthyroidism Association (HPA).
• "Our deepest gratitude goes out to the patients, their caregivers, investigators, and study staff who have made this groundbreaking CALIBRATE study possible and continue to contribute to this pivotal research in ADH1. We are extremely encouraged by the robust and positive findings of this registrational study, which underscore the potential for encaleret to meaningfully improve the lives of people living with ADH1. We look forward to working closely with health authorities to bring encaleret to patients as quickly as possible." Scott H. Adler, M.D., Chief Medical Officer of Calcilytix (a BridgeBio affiliate).

Industry Context

The positive Phase 3 results for encaleret in ADH1 position BridgeBio as a leader in developing targeted therapies for rare genetic diseases. ADH1, a form of hypoparathyroidism, currently relies on conventional therapies (calcium supplements and active vitamin D) that manage symptoms but do not address the underlying cause or fully normalize calcium and PTH levels while also managing urine calcium. Encaleret's mechanism of action, as a negative allosteric modulator of the CaSR, offers a novel approach that could significantly improve patient outcomes and establish a new standard of care in this underserved patient community, potentially expanding into broader hypoparathyroidism indications.

Comparison to Industry Standards

• Encaleret demonstrated superior efficacy compared to conventional therapy (calcium supplements and active vitamin D) in achieving target serum and urine calcium levels (76% vs. 4%).
• Unlike conventional therapy, encaleret not only increased and maintained blood calcium and endogenous parathyroid hormone (PTH) but also decreased and maintained urine calcium in the normal range, addressing a critical unmet need in ADH1 management.
• The high rate of participants (97%) electing to continue in the long-term extension study suggests a strong perceived benefit over existing treatments.

Stakeholder Impact

• Shareholders: Highly positive impact due to successful Phase 3 results, de-risking the drug, and potential for significant future revenue from a new standard of care in ADH1 and potentially other hypoparathyroidism indications.
• Patients with ADH1: Significant positive impact, as encaleret offers a targeted therapy that addresses the underlying cause of ADH1, potentially normalizing calcium and PTH levels while reducing urine calcium, leading to improved quality of life and reduced complications compared to conventional therapy.
• Caregivers: Positive impact through improved patient health and potentially reduced burden of managing complex conventional therapies.
• Healthcare Providers: Encaleret could become an important new standard of care, providing a more effective and targeted treatment option for ADH1 patients.

Next Steps

• Submit New Drug Application (NDA) to the FDA in the first half of 2026.
• Submit Marketing Authorization Application (MAA) to the EMA following the NDA.
• Initiate a registrational trial of encaleret in pediatric ADH1 in Q1 2026.
• Initiate a Phase 3 study of encaleret in adults with chronic hypoparathyroidism in 2026.
• Host an investor call on October 29, 2025, at 8:00 am ET to discuss results.

Key Dates

Recommendation

The filing details exceptionally strong and statistically significant positive Phase 3 topline results for encaleret in ADH1, meeting all primary and key secondary endpoints with a favorable safety profile. This represents a major de-risking event for the drug, indicating a high probability of regulatory approval and substantial market potential in an orphan disease with significant unmet needs. The planned expansion into pediatric ADH1 and chronic hypoparathyroidism further enhances the long-term growth prospects. Given the robust clinical data and clear path to market, the stock is poised for significant upside, warranting a 'strong buy' recommendation for investors seeking exposure to innovative rare disease therapies.

Keywords

BridgeBio Pharma, BBIO, Encaleret, Autosomal Dominant Hypocalcemia Type 1, ADH1, Phase 3, CALIBRATE study, Genetic Diseases, Hypoparathyroidism, Calcium-sensing receptor, CaSR, Orphan Drug, Fast Track Designation, Biopharmaceutical