Data Readout

Tectonic's TX45 heads to PH-HFpEF data test with no validated mechanism in the field

The APEX Phase 2 trial pits Tectonic's relaxin-receptor fusion protein against placebo in a heart-failure subtype where no therapy has yet shown a validated hemodynamic benefit.

By AppliedXLJuly 13, 2026Trial NCT06616974

Executive Summary

Tectonic's Phase 2 trial of TX45 in PH-HFpEF is heading toward a topline readout that will test whether a relaxin-receptor fusion protein can move pulmonary vascular resistance and exercise capacity against placebo in a heart-failure subtype with no established disease-modifying therapy.
No competitor program shares TX45's target or its Fc-fusion delivery format in this indication, and prior vasodilator approaches tested in the related HFpEF pulmonary hypertension population have not established a placebo-corrected benefit.
The trial's enrollment target, completion timeline, and protocol design have stayed stable since initiation, meaning execution is not the open question here; the open question is what the data show.
A readout that clears a meaningful placebo-corrected margin on the trial's hemodynamic and functional measures would be the first evidence that targeting the relaxin receptor changes the underlying biology of this heart-failure subtype, rather than simply adding another symptomatic vasodilator.

The trial

Tectonic Therapeutic, Inc. is running APEX, a randomized, placebo-controlled Phase 2 trial of TX45 in patients with pulmonary hypertension secondary to heart failure with preserved ejection fraction, registered as NCT06616974. The trial enrolls adults with a six-minute walk distance between 100 and 450 meters and NYHA class II-III heart failure, randomizing them across two TX45 dose arms and a placebo comparator. Enrollment is targeted at 180 patients across sites in the United States, Australia, and multiple European countries, with a primary completion date of October 9, 2026 and full study completion guided for November 20, 2026. NCT06616974

Probability of Success

Endpoint Met89%

Completes79%

Clinical Significance28%

Regulatory33%

What it tests

The trial's primary endpoints center on safety, tracking adverse events, adverse events of special interest, and treatment-related laboratory abnormalities, alongside a clinical measure: mean change from baseline in pulmonary vascular resistance in patients with combined pre- and post-capillary pulmonary hypertension. Secondary endpoints add exercise capacity, cardiac output, pulmonary capillary wedge pressure, NT-proBNP, and patient-reported outcomes on the Kansas City Cardiomyopathy Questionnaire. Tectonic said in its first-quarter 2026 update that APEX enrollment is nearing completion, with topline results anticipated in late Q4 2026 or early Q1 2027. NCT06616974+1

The field

No trial in the competitive landscape shares TX45's RXFP1 target and Fc-relaxin fusion modality within PH-HFpEF; the nearest program sharing the RXFP1 target, Moderna's mRNA-0184, sits in Phase 1 for a different mechanism and population. Within PH-HFpEF and the closely related PH-HFpEF label used by Tenax Therapeutics for levosimendan, the only other active programs are Tenax's two Phase 3 levosimendan trials, an inotropic mechanism distinct from TX45's receptor-agonist approach.

The bar

Across the broader pulmonary hypertension field, vasodilator and prostacyclin-pathway drugs including selexipag, macitentan, riociguat, sotatercept, and sildenafil have posted placebo-corrected six-minute walk distance gains ranging from 12 to 45 meters in Group 1 pulmonary arterial hypertension trials, while sildenafil tested specifically in Group 2 HFpEF-associated pulmonary hypertension in the RELAX trial showed a 3-meter decline versus placebo. With no validated disease-modifying mechanism established for PH-HFpEF specifically, and with the nearest same-population precedent, sildenafil in RELAX, having failed to separate from placebo, a walk-distance or hemodynamic result for TX45 that clears the 30-meter placebo-corrected threshold cited in pulmonary hypertension literature would be the finding that distinguishes it from that history. Falling short of that margin, or trailing toward the RELAX result, would extend the pattern of vasodilator strategies not translating from Group 1 pulmonary arterial hypertension into the HFpEF-associated form of the disease.

Trial stability

The registry shows no changes to the primary completion date and no enrollment growth beyond the original 180-patient target, a pattern the operational model treats as within the routine band rather than as a delay or a redesign signal. Tectonic's pipeline update also disclosed that TX45 has moved into a second indication, PH-ILD, under a separate open-label Phase 2 trial (ALPINE), while a related molecule, TX2100, is in Phase 1a testing for hereditary hemorrhagic telangiectasia. Tectonic

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