New Heart Failure Drug TX45 Completes Phase 2 Enrollment Across 14 Countries

Heart failure with preserved ejection fraction is one of the most common and undertreated forms of heart disease, particularly in older adults. When it combines with pulmonary hypertension — elevated pressure in the blood vessels of the lungs — outcomes become significantly worse and treatment options are extremely limited. TX45 is being developed specifically for this high-need population.

Tectonic Therapeutic has completed enrollment in the APEX Phase 2 clinical trial, bringing in 191 patients across 14 countries. The trial is randomized, double-blind, and placebo-controlled — the gold standard design for evaluating a new drug. Patients receive either 300 mg of TX45 subcutaneously once monthly, every other week, or a placebo. The primary measure of success is change in pulmonary vascular resistance, a key indicator of how hard the heart must work to push blood through the lungs.

TX45 is classified as a long-acting Fc-relaxin fusion protein. It works by activating the RXFP1 receptor, which plays a role in vascular relaxation, reducing fibrosis (scarring), and dampening inflammation. These combined mechanisms address several of the root physiological problems in PH-HFpEF simultaneously, which is what makes it a potentially differentiated therapy.

About 72% of enrolled patients — 137 out of 191 — had a baseline pulmonary vascular resistance above 3 Wood Units, placing them in the more severe disease category. This enriched enrollment strategy improves the likelihood of detecting a meaningful treatment signal in the primary endpoint analysis.

Topline results from the APEX trial are anticipated in early Q1 2027. While this is still a Phase 2 trial and therefore not definitive proof of efficacy or safety, a positive readout would be a significant milestone for a condition that urgently needs new therapeutic options. Health-conscious adults with cardiovascular risk factors should watch this space closely.