Tenax Therapeutics has suffered a major Phase 3 setback after TNX-103, its oral formulation of levosimendan, failed to significantly improve exercise capacity in patients with pulmonary hypertension caused by heart failure with preserved ejection fraction. The 241-patient LEVEL trial also missed its key secondary endpoint measuring patient-reported heart failure symptoms, leaving the company without the broad pivotal efficacy result it had hoped could support a regulatory filing. Tenax Therapeutics is now focusing on prespecified analyses suggesting greater benefit among patients with more severe disease, while preparing to ask the United States Food and Drug Administration whether an enriched Phase 3 strategy can preserve the program.
The market reaction was severe. Tenax Therapeutics shares were trading near $1.42 during the August 10 session, down approximately 89.5% from the previous close, after falling as low as $1.34. The collapse reflects the importance investors had placed on LEVEL as a potentially registrational study in a disease for which no therapy is currently approved specifically for pulmonary hypertension associated with heart failure with preserved ejection fraction.
The failed primary analysis does not mean TNX-103 showed no biological activity. Patients with lower baseline walking capacity appeared to derive a substantially larger benefit, while cardiac stress and pulmonary-pressure biomarkers moved favorably across the overall study population. Those findings give Tenax Therapeutics a scientific argument for continued development, but they cannot erase the statistical failure of the trial’s prespecified primary and key secondary endpoints.
LEVEL produced only a 3.5-meter placebo-adjusted improvement in its primary analysis
LEVEL was a randomized, double-blind, placebo-controlled Phase 3 trial conducted at 41 sites in the United States and Canada. A total of 241 patients received either TNX-103 or placebo, beginning with one milligram twice daily and increasing to one milligram three times daily from week five when tolerated. The primary endpoint measured change in six-minute walk distance at week 12.
Patients receiving TNX-103 improved by an adjusted 14 meters compared with 10.4 meters for placebo. The resulting 3.5-meter treatment difference was not statistically significant, with a p-value of 0.63. The trial had previously been described as having more than 90% statistical power to identify a clinically meaningful 25-meter treatment difference, making the small separation particularly disappointing.
The key secondary endpoint also failed. Kansas City Cardiomyopathy Questionnaire total symptom scores improved by 6.6 points with TNX-103 and 6.5 points with placebo, producing essentially no treatment difference. That result weakens the possibility that a small walk-distance effect was accompanied by a meaningful improvement in how patients felt or functioned.
The negative results matter because LEVEL was designed as a registrational trial rather than an exploratory Phase 2 study. Tenax Therapeutics had previously reached agreement with the United States Food and Drug Administration that a single Phase 3 study achieving a sufficiently strong statistical result could potentially support a New Drug Application. LEVEL did not provide that result.
Patients with poorer exercise capacity produced the strongest argument for continuing TNX-103
A prespecified analysis divided patients around the median baseline walking distance of 333 meters. Among the 119 patients who entered the study below that threshold, TNX-103 produced a placebo-adjusted improvement of 26.3 meters, with a nominal p-value of 0.0112. Patients receiving TNX-103 improved by an average 26.7 meters while those receiving placebo declined by 2.6 meters.
Older participants also appeared to respond more strongly. Patients aged at least 71 years showed a 27.1-meter placebo-adjusted advantage, while those in the oldest age tertile produced a 37.6-meter difference. These observations support Tenax Therapeutics’ hypothesis that TNX-103 may work better in patients with more advanced disease and lower functional capacity.
The company’s argument is biologically plausible, but subgroup evidence must be interpreted cautiously after a failed primary endpoint. Even prespecified analyses can produce findings that appear more persuasive than they ultimately prove to be when tested prospectively. Tenax Therapeutics will need to define the proposed severe-disease population before another trial begins and then reproduce the benefit in that selected group.
A post hoc quartile analysis reinforced the pattern but carries even greater uncertainty. The apparent treatment effect declined progressively as baseline exercise capacity increased, from a 32.4-meter advantage among patients walking 264 meters or less to a negative 27.3-meter difference in the highest-functioning quartile. Because this analysis was conducted after the primary assessment, it is useful for generating a future trial hypothesis rather than establishing efficacy.
Cardiac biomarkers showed clear activity even though patients did not meet the main clinical goals
TNX-103 produced a 49% placebo-adjusted reduction in N-terminal pro-B-type natriuretic peptide, a blood biomarker associated with cardiac wall stress. The difference carried a nominal p-value below 0.0001. Right ventricular systolic pressure also declined by 3.5 millimeters of mercury versus placebo across the overall population and by 4.9 millimeters of mercury among participants with baseline walking distance below 333 meters.
These findings indicate that oral levosimendan was affecting cardiovascular physiology even though that activity did not translate into a statistically significant improvement in the trial’s primary functional endpoint. TNX-103 acts as both a calcium sensitizer and potassium-channel activator, with effects intended to improve cardiac performance and vascular function.
The biomarker evidence could become important in discussions with regulators, but Tenax Therapeutics explicitly noted that the associated nominal p-values were not adjusted for multiple comparisons and do not establish efficacy. Biomarker improvements cannot substitute automatically for a failed clinical endpoint unless regulators agree that a particular measure can support the required evidence of treatment benefit.
Safety provided fewer surprises. Adverse events occurred in 86.7% of TNX-103 recipients compared with 71.9% of placebo recipients, while treatment-related events occurred in 38.3% and 17.4%, respectively. Serious adverse events were nearly identical at 10.8% and 10.7%, and Tenax Therapeutics reported no new safety signal.
FDA discussions will determine whether LEVEL becomes a dead end or a trial-design lesson
Tenax Therapeutics plans to request a Type C meeting with the United States Food and Drug Administration and seek scientific advice from the European Medicines Agency. The company intends to propose enriching future enrollment for patients with greater disease severity, using the LEVEL subgroup findings to redefine the population most likely to benefit.
The ongoing LEVEL-2 Phase 3 study now becomes particularly important. Tenax Therapeutics will need to determine whether its design can be modified appropriately and whether regulators consider the subgroup evidence strong enough to justify continuing the registrational program. Any major protocol change could affect enrollment, timelines, statistical assumptions and development costs.
The company entered the readout from a comparatively strong cash position. Tenax Therapeutics reported $118 million in cash and cash equivalents at June 30, helped by $13.4 million of warrant-exercise proceeds during the second quarter, and had projected funding through the second quarter of 2028. That runway gives management some capacity to respond to the setback without immediately returning to capital markets.
The nearly 90% share-price collapse nevertheless shows how dramatically the investment case has changed. Tenax Therapeutics had a market capitalization of roughly $72 million during Monday trading, leaving investors assigning far less value to the probability of TNX-103 reaching the market than they did before the readout.
LEVEL does not necessarily end oral levosimendan development in pulmonary hypertension associated with heart failure with preserved ejection fraction. It does force Tenax Therapeutics to prove prospectively that the apparent benefit in sicker patients is real rather than an attractive subgroup finding emerging from an otherwise negative pivotal study. Until regulators agree on that path and another trial confirms the effect, TNX-103 has moved from a potentially near-registration asset back into a high-risk clinical-development story.
