Tovinontrine misses heart-failure biomarker endpoint in preserved-ejection-fraction trial

An experimental heart-failure drug failed to improve its primary blood-marker endpoint in a randomized Phase 2 trial, despite evidence that it affected its intended signaling pathway. Results presented October 11 at the Heart Failure Society of America meeting in Phoenix leave the clinical value of tovinontrine uncertain and raise questions about which doses deserve further testing.

The findings matter for efforts to preserve cardiovascular health and function in older adults. Participants in the Cycle-2-PEF trial averaged 72 years of age, according to October 12 conference coverage by HCPLive. The study assessed a biological marker over 12 weeks; it did not establish that treatment helps people live longer or remain independent.

### What the trial tested

Cycle-2-PEF was a randomized, double-blind, placebo-controlled study in adults with chronic heart failure described by the investigators as having preserved ejection fraction. It assigned 277 participants to tovinontrine or placebo alongside existing treatment.

The UK Health Research Authority’s study summary identifies the primary endpoint as the change in blood NT-proBNP over 12 weeks compared with placebo. This marker is used to assess heart failure, but a change in its concentration is not itself a direct measurement of symptoms, hospitalization or survival.

The authority’s summary also explains why a placebo comparison was necessary: NT-proBNP can change during follow-up without the experimental drug. Consequently, a decline from a participant’s starting value cannot by itself establish a treatment effect.

Tovinontrine inhibits phosphodiesterase-9, or PDE9. Cardurion Pharmaceuticals, its developer, is investigating whether this approach can enhance natriuretic peptide signaling in heart muscle cells. The program tests whether that biological rationale translates into useful effects when patients already receive established heart-failure therapy.

### Biological activity without the intended result

Cardurion reported no significant NT-proBNP effect in Cycle-2-PEF. HCPLive’s account reported a median 40% increase in plasma cGMP, a signaling molecule, by week 12. Together, those findings illustrate a central distinction in drug development: affecting a pathway does not guarantee improvement in the outcome selected to test efficacy.

The companion Cycle-1-REF trial examined three dose levels in patients with reduced ejection fraction. Its reported population included 529 participants with an average age of 69. Cardurion emphasized larger NT-proBNP reductions at the lower dose levels and an absence of benefit at the highest level.

The statistical uncertainty remains consequential. HCPLive reported that the confidence intervals for NT-proBNP changes at all three dose levels included zero. The lowest-dose group contained only 53 participants. Those results support further investigation rather than a firm conclusion that a particular dose provides clinical benefit.

### A hypothesis for the next study

Investigators proposed that stronger pathway stimulation might trigger counter-regulatory responses that limit downstream effects. This is an explanation to test, not an established mechanism demonstrated by the clinical findings. A pattern suggesting greater activity at lower doses needs prospective confirmation.

Cardurion described safety and tolerability as favorable in both trials. Its announcement did not provide detailed adverse-event tables, limiting independent assessment of that characterization. Short follow-up also leaves longer-term safety unresolved.

The available evidence consists of conference findings, a sponsor announcement and specialist coverage, supported by an official study-design record. That is enough to report the mixed results, but not to treat the program as validated therapy. For healthspan research, the next meaningful question is whether a reproducible biological effect can ultimately produce improvements patients experience, including better function and fewer serious heart-failure events.