Data Readout

Tectonic's TX45 heads to Q1 2027 readout after full enrollment in PH-HFpEF

The Phase 2 APEX trial enrolled 191 patients with topline data due by March 2027, testing whether an Fc-relaxin fusion protein can move pulmonary vascular resistance in a disease with no approved therapy.

By AppliedXLJuly 13, 2026Trial NCT06616974

Executive Summary

Tectonic Therapeutic has finished enrolling its Phase 2 test of TX45 in pulmonary hypertension linked to heart failure with preserved ejection fraction and expects to report results within the next several months.
The trial is built around a hemodynamic marker of vascular resistance in a population enriched for the more severe combined pre- and post-capillary form of the disease, rather than the exercise-capacity endpoints that failed for at least one prior approved drug in this same setting.
TX45 has no in-class competitor at a comparable stage: the field's few other programs targeting this receptor sit in earlier testing, leaving this readout as the closest thing to a proof-of-concept test for the mechanism in this disease.
Because no therapy has established a validated disease-modifying effect in this pulmonary hypertension subtype, a resistance reduction that also moves functional capacity past the threshold that separates a real signal from noise is what would make this result informative rather than merely directional.

The catalyst

Tectonic Therapeutic said on June 10, 2026 that it completed enrollment in the APEX trial, a 24-week, randomized, double-blind, placebo-controlled Phase 2 study of TX45 in pulmonary hypertension associated with heart failure with preserved ejection fraction, known as PH-HFpEF. The trial enrolled 191 patients across 14 countries, exceeding its 180-patient target listed in the registry. Alise Reicin, Tectonic's president and chief executive, called full enrollment "a critical milestone for our TX45 clinical development program" and said topline results are expected in early Q1 2027. That guidance, delivered in June 2026, sits inside the Q1 2027 window Tectonic has since reiterated. Tectonic+1

Probability of Success

Endpoint Met89%

Completes79%

Clinical Significance28%

Regulatory33%

The design

APEX randomizes patients to one of two subcutaneous TX45 dose regimens, 300 mg once monthly or 300 mg every other week, or placebo. The trial enriched for a more severe phenotype: 137 of the 191 enrolled patients, about 72%, have combined pre- and post-capillary pulmonary hypertension with baseline pulmonary vascular resistance above 3 Wood units. Mean baseline PVR was 4.2 Wood units in the overall population and 5.2 Wood units in that enriched subgroup. The registered primary endpoint set spans safety measures, adverse-event and laboratory monitoring, and the mean change from baseline in pulmonary vascular resistance in the combined pre- and post-capillary subgroup. The trial's registered primary completion date is October 9, 2026, ahead of the topline data Tectonic has guided to for the following quarter. NCT06616974+1

The competitive frame

No trial shares both TX45's RXFP1 target and its mechanism class at a comparable stage. Moderna's mRNA-0184, an mRNA therapy directed at the same receptor, remains in a Phase 1 safety and tolerability study in healthy participants, and a Phase 1 relaxin program in preeclampsia from Corthera closed years ago. Within PH-HFpEF itself, the closest active program is Tenax Therapeutics' Phase 3 levosimendan studies, which work through a different mechanism, calcium sensitization and potassium-channel activity, rather than relaxin-receptor signaling. TX45 has no direct same-target, same-phase comparator in human testing.

The bar

Pulmonary vascular resistance is a physiologic marker, not a validated clinical outcome, in PH-HFpEF. A curated set of trials in pulmonary arterial hypertension, a related but distinct disease group, shows placebo-corrected six-minute walk distance gains ranging from 12 meters for selexipag to 45 meters for sildenafil, against a literature-based minimal clinically important difference of 30 meters. Sildenafil itself, when tested specifically in HFpEF-associated pulmonary hypertension in the RELAX trial, showed a 3-meter decline versus placebo, underscoring that efficacy in Group 1 pulmonary arterial hypertension does not carry over to this Group 2 setting. With no therapy having established a disease-modifying effect in PH-HFpEF, a PVR reduction in APEX that is paired with a functional-capacity or symptom gain clearing that same benchmark, rather than resistance change alone, is the result that would distinguish TX45 from the RELAX precedent.

Timing and stability

The trial's registry record shows no primary completion date changes and no post-completion changes to the primary outcome measure, and it carries a Stable protocol designation with a low registry-churn signal count. Enrollment landed at its 180-patient anticipated target with no growth or shortfall, a change the operational risk model flags only outside a plus-or-minus 20% band, so this reads as a routine, on-plan completion of enrollment rather than an operational concern. NCT06616974

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