Why Tectonic Therapeutic Stock Soared 30% After-Hours Today

• TX45, Tectonic’s experimental Fc-relaxin fusion protein, showed strong improvements in heart and lung function with no serious safety issues in patients with heart failure-related pulmonary hypertension.
• The results expand the drug’s potential reach to a broader patient population with no approved therapies, while the Phase 2 APEX trial continues toward results in 2026.
• Retail investors reacted enthusiastically on Stocktwits, calling the data “unbelievable” and “outstanding.” 

Shares of Tectonic Therapeutic rose about 30% in after-hours trading on Wednesday after the company reported positive topline results from a Phase 1b Part B clinical trial of TX45, its experimental Fc-relaxin fusion protein, in patients with Group 2 pulmonary hypertension associated with heart failure with reduced ejection fraction.

TX45 Shows Improvements In Heart And Lung Function

Tectonic said a single intravenous dose of TX45 was well tolerated, with no serious side effects or meaningful changes in blood pressure. The treatment showed clear benefits for heart and lung function by reducing pressure on the heart and lungs and improving blood flow. Key measures, such as pulmonary capillary wedge pressure, total pulmonary resistance, and mean pulmonary artery pressure, all decreased, while cardiac output increased.

CEO Alise Reicin said the findings “open up the potential to expand into this additional patient population with significant unmet need and no approved therapies,” adding that the results mirrored those seen in an earlier TX45 study in heart failure with preserved ejection fraction.

Broader Development Plan

The trial enrolled 14 patients and builds on earlier positive data from TX45’s Phase 1b Part A study in ejection fraction. The company is currently running the APEX Phase 2 trial to test TX45 over a 24-week treatment period in patients with ejection fraction, with topline results expected in 2026.

Chief Medical Officer Marcella Ruddy said the drug showed “persistent effects at day 29” based on echocardiographic data and continued to demonstrate a favorable safety profile.

Stocktwits Users Cheer Tectonic’s TX45 Results

On Stocktwits, retail sentiment for Tectonic Therapeutic was ‘extremely bullish’ amid ‘extremely high’ message volume.

One user described the TX45 results as “unbelievable,” predicting the stock could reach $50. 

Another user said the data looked “outstanding,” adding to their position below $22 and expecting the shares to climb further.

Tectonic’s stock has declined 60% so far in 2025.

For updates and corrections, email newsroom[at]stocktwits[dot]com.

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