BridgeBio's Double Success: Thyroid Drug Shines in Phase III, Shares Soar

BridgeBio Pharma, Inc. has reported impressive Phase III results for its thyroid drug encaleret, marking the company's second major success this week. The genetic disease biotech's shares have surged nearly 8% following the announcement, building on momentum from earlier positive results in limb-girdle muscular dystrophy.

Encaleret Exceeds Expectations in Autosomal Dominant Hypocalcemia Type 1

In a pivotal Phase III trial, encaleret demonstrated remarkable efficacy in treating autosomal dominant hypocalcemia type 1 (ADH1), a rare genetic thyroid disorder. The CALIBRATE study, involving 70 adult patients, showed that 76% of participants receiving encaleret achieved target serum and urine calcium levels at week 24, compared to just 4% in the standard of care group.

Mizuho analysts noted that these results surpassed both investor and company expectations, describing it as an "upside case scenario." The drug's performance even improved upon its Phase II results, a notable achievement given that Phase III outcomes typically fall short of earlier trial data.

Encaleret's rapid action was particularly impressive, with 71% of participants reaching target values by day three and 98% by week 20. The therapy also demonstrated a favorable safety profile, with no discontinuations and 97% of participants opting to continue into a long-term extension study.

Market Potential and Regulatory Outlook

BridgeBio plans to submit a regulatory application to the FDA in the first half of 2026, potentially leading to approval in early 2027. Analysts project significant market potential for encaleret, with Mizuho estimating peak sales of $750 million in ADH1, while Jefferies suggests a more optimistic figure of $1 billion or more.

The company estimates that there are approximately 9,000 symptomatic ADH1 patients in the U.S., with about 3,000 currently diagnosed. As BridgeBio progresses towards regulatory submission, it will continue studying encaleret in chronic hypoparathyroidism and pediatric ADH1.

A Week of Wins: Muscular Dystrophy and ATTR-CM Success

BridgeBio's encaleret triumph follows closely on the heels of another significant achievement. Earlier this week, the company announced positive Phase II results for BBP-418, an oral small molecule treatment for limb-girdle muscular dystrophy (LGMD). The drug doubled a key biomarker indicating muscle stabilization and reduced another marker of muscle damage.

Adding to its growing portfolio, BridgeBio is also seeing success with Attruby, approved in November 2024 for treating transthyretin amyloid cardiomyopathy (ATTR-CM). Despite entering a competitive market, Attruby has performed well, generating $71.5 million in sales in the second quarter from 3,751 unique patient prescriptions in the U.S. Analysts anticipate continued growth, with Jefferies predicting third-quarter sales of $102 million and suggesting that Attruby could become "a first-line $4 billion+ pill" in a market with a $20 billion opportunity.

As BridgeBio prepares to release its third-quarter financial results, the company's recent clinical successes and growing commercial presence position it as a significant player in the genetic disease and rare disorder therapeutic landscape.