Tenax Therapeutics Phase 3 Trial Fails Primary Endpoint

What happened

Tenax Therapeutics announced results from its 241-patient Phase 3 LEVEL trial evaluating TNX-103 in pulmonary hypertension associated with heart failure with preserved ejection fraction (PH-HFpEF). At Week 12, patients treated with TNX-103 improved their six-minute walk distance by 14.0 meters from baseline compared with 10.4 meters for placebo, yielding a treatment difference of just 3.5 meters with a p-value of 0.63-failing to reach statistical significance. The trial also missed its key secondary endpoint, with the Kansas City Cardiomyopathy Questionnaire total symptom score improving by 6.6 points on TNX-103 versus 6.5 points on placebo, a difference of only 0.1 points. TNX-103 was reported as generally safe and well tolerated, with no new safety signals. There are currently no approved treatments specifically for PH-HFpEF, which is typically managed with standard heart failure therapies.

Why it matters

The trial failure represents a major setback for Tenax's lead drug candidate and its effort to address an unmet medical need in heart failure. The lack of efficacy on both primary and key secondary endpoints leaves the company without clear evidence that TNX-103 works broadly in the intended patient population. However, prespecified subgroup analyses showed that patients with baseline six-minute walk distance below 333 meters experienced a 26.3-meter placebo-adjusted improvement with a nominal p-value of 0.0112, and patients aged 71 or older showed a 27.1-meter treatment difference. Additionally, exploratory biomarker analyses indicated TNX-103 produced a 49% greater reduction in NT-proBNP, a blood marker of heart stress, and reduced right ventricular systolic pressure by 3.5 mmHg versus placebo. Company management attributed the overall negative result to dilution of the treatment effect by including healthier patients and suggested the drug may have worked too well in less severe cases by lowering blood volume to levels that limited exercise capacity. These findings have prompted Tenax to pursue a revised registrational strategy focused on patients with greater disease burden.

Bigger picture

Heart failure with preserved ejection fraction represents roughly half of all heart failure cases and is particularly difficult to treat. Pulmonary hypertension in this population further complicates disease management and is associated with worse outcomes. The absence of approved therapies specifically targeting PH-HFpEF reflects the challenge of demonstrating benefit in this heterogeneous patient group. Tenax's trial adds to a body of evidence suggesting that disease severity and patient selection criteria are critical variables in heart failure drug development. The company's chief medical officer noted that the drug may have worked differently across the disease spectrum, an observation that could inform both Tenax's next steps and broader clinical trial design in the field. The company now plans to request a Type C meeting with the FDA to discuss protocol amendments to its ongoing second study, potentially excluding patients with less severe disease. This regulatory reset will determine whether a more narrowly defined patient population can support approval.

What to watch

Investors should monitor the outcome of Tenax's planned Type C meeting with the FDA, which will clarify whether the agency accepts the subgroup findings as a basis for revising the development programme. Any protocol amendments to the ongoing second registrational study, particularly changes to patient eligibility criteria to enrich for more severe disease, will be key indicators of the path forward. Additional analyses from the LEVEL trial, including detailed biomarker and hemodynamic data, may provide further insight into which patients are most likely to benefit. The company's ability to secure financing to support a revised development plan will also be critical, especially given the sharp market reaction to the trial results. Finally, any competitive developments in PH-HFpEF or related heart failure indications could influence the commercial opportunity if TNX-103 eventually reaches approval.