TNX-103 Phase 3 failure forces Tenax into FDA reset after nearly 90% stock plunge

A pivotal clinical failure has erased most of Tenax Therapeutics’ market value and forced the company to rethink how it develops TNX-103 for pulmonary hypertension associated with heart failure with preserved ejection fraction. The Phase 3 LEVEL trial missed both its primary exercise-capacity endpoint and its key patient-reported symptom endpoint, undermining the broad registration strategy investors had been expecting. Tenax Therapeutics is now relying on a prespecified subgroup of patients with worse baseline exercise capacity, where treatment produced a 26.3-meter placebo-adjusted improvement in six-minute walk distance, to support discussions with regulators about a narrower development plan. Shares collapsed almost 90% on August 10, showing that investors currently assign far less probability to TNX-103 reaching the market despite favorable cardiac biomarker and pulmonary-pressure findings.

The setback is particularly consequential because TNX-103 is essentially the company’s central value-driving asset. Tenax Therapeutics owns global rights to levosimendan and has positioned oral TNX-103 as a potential first approved treatment specifically for pulmonary hypertension associated with heart failure with preserved ejection fraction. The company still has $118 million in cash and an ongoing second Phase 3 study, LEVEL-2, giving it enough resources to attempt a recovery rather than abandon development immediately. Whether that cash now funds a successful regulatory reset or a prolonged effort around a drug with insufficient efficacy has become the central question for shareholders.

LEVEL missed both endpoints that mattered most to the original TNX-103 approval strategy

LEVEL randomized 241 patients across 41 sites in the United States and Canada to TNX-103 or placebo. Patients began with one milligram twice daily before increasing to one milligram three times daily from week five when tolerated, while the primary analysis measured change in six-minute walk distance after 12 weeks.

The adjusted improvement was 14.0 meters for TNX-103 compared with 10.4 meters for placebo. That left a placebo-adjusted difference of only 3.5 meters and a p-value of 0.63, far from statistical significance and substantially below the magnitude Tenax Therapeutics had designed the study to detect.

The key secondary endpoint offered no compensating evidence. Kansas City Cardiomyopathy Questionnaire total symptom scores improved by 6.6 points with TNX-103 and 6.5 points with placebo, creating an adjusted difference of just 0.1 point. The failure across both exercise capacity and symptoms makes it harder to argue that the overall patient population experienced a clinically meaningful treatment effect that simply escaped statistical significance.

That matters commercially as well as scientifically. Tenax Therapeutics previously said the United States Food and Drug Administration had agreed that a single successful Phase 3 study producing a p-value of 0.01 could potentially support a New Drug Application in this indication. LEVEL did not deliver anything close to that threshold in its primary population, so management can no longer proceed as if the original registrational strategy remains intact.

The company instead plans to request a Type C meeting with the United States Food and Drug Administration to discuss revisions to the ongoing development program. Regulatory feedback will determine whether LEVEL can still contribute meaningfully to an eventual filing or whether Tenax Therapeutics effectively needs another prospectively successful pivotal trial in a newly defined population.

The 26.3-meter subgroup benefit gives TNX-103 a rescue hypothesis but not a rescue yet

The strongest case for continuing development comes from patients whose baseline six-minute walk distance was below the trial median of 333 meters. In this prespecified subgroup, TNX-103 produced a 26.3-meter placebo-adjusted improvement, with a 95% confidence interval ranging from 6.0 to 46.7 meters and a nominal p-value of 0.0112.

Tenax Therapeutics interprets the result as evidence that patients with greater disease burden were more responsive to the drug. Management has indicated that the original enrollment criteria brought too many relatively higher-functioning patients into LEVEL and that a future enriched population could focus on people with more severe exercise limitation.

That explanation is plausible, but it must now survive prospective testing. A subgroup can look compelling even when defined before the database is analyzed, particularly after the full trial has failed. Regulators will want evidence that the below-333-meter threshold reflects a reproducible biological or clinical distinction rather than a favorable division of one negative dataset.

The subgroup finding becomes more interesting when considered alongside the biological results. Across the overall trial, TNX-103 produced a 49% greater reduction in N-terminal pro-B-type natriuretic peptide compared with placebo, with a nominal p-value below 0.0001. The drug also reduced right ventricular systolic pressure by 3.5 millimeters of mercury relative to placebo, with a nominal p-value of 0.0045.

Those findings indicate that oral levosimendan was producing measurable cardiovascular effects even though the overall study failed to demonstrate a significant improvement in walking capacity. They strengthen the argument that TNX-103 is pharmacologically active, but pharmacological activity is not enough for approval when the principal clinical outcome fails.

The disconnect between biomarkers and functional performance will likely become a major topic in the FDA meeting. Tenax Therapeutics must show that selecting patients with more advanced disease converts those biological effects into repeatable improvements that matter clinically.

Safety gives the company one less problem to solve. Tenax Therapeutics reported that TNX-103 was generally safe and tolerated, with serious adverse events and adjudicated clinical-worsening events balanced between treatment groups. The absence of a major new safety signal allows the regulatory discussion to focus primarily on efficacy, population selection and study design rather than whether exposure to the medicine itself is unacceptable.

LEVEL-2 now carries more risk as Tenax decides whether to change an ongoing Phase 3 trial

The failure arrives while LEVEL-2, the company’s second global Phase 3 trial, is already underway. Before the LEVEL readout, Tenax Therapeutics expected enrollment in LEVEL-2 to be completed by the end of 2027. The study was intended to strengthen the registration package and expand the global evidence supporting oral levosimendan.

LEVEL has changed the strategic purpose of that study. Tenax Therapeutics must now determine whether LEVEL-2 can be modified to enrich for patients with greater disease severity and whether doing so would preserve its regulatory and statistical integrity. A substantial protocol amendment could affect recruitment, timelines, sample-size assumptions and the amount of additional capital required.

The existing cash position gives management flexibility. Tenax Therapeutics ended June with approximately $118 million in cash and cash equivalents after receiving $13.4 million from warrant exercises during the second quarter. Management previously expected those resources to finance operations through the second quarter of 2028.

Development costs were already increasing before the setback. Second-quarter research and development expenses more than doubled to $12.9 million from $6.1 million a year earlier as spending increased on LEVEL and LEVEL-2. The quarterly net loss widened to $17.8 million from $10.9 million.

That means Tenax Therapeutics is better funded than many small biotechnology companies facing a pivotal failure, but the cash is no longer supporting the same development plan investors expected two weeks ago. A redesigned trial, delayed filing and extended regulatory process could consume a meaningful portion of the runway before TNX-103 reaches another decisive readout.

Shareholders also have to consider the company’s capital structure. Tenax Therapeutics had approximately 31.9 million common shares outstanding at June 30, up sharply from about 9.3 million at the end of 2025, reflecting substantial warrant exercises and share issuance. Additional warrant exercises occurred after the quarter ended, bringing in further cash but increasing the share count.

The strengthened balance sheet therefore came partly through shareholder dilution. If development extends beyond the current runway, another capital raise could eventually become necessary unless Tenax Therapeutics obtains partnership funding or other non-dilutive capital.

Nearly 90% stock collapse shows investors have drastically cut TNX-103 approval odds

Tenax Therapeutics shares were trading around $1.38 late on August 10, down approximately 89.7% from the previous close. The stock traded as low as $1.34 after opening around $1.77, with more than 63 million shares changing hands. The company’s market capitalization fell to roughly $70 million.

That market value is now substantially below the $118 million cash balance Tenax Therapeutics reported at the end of June. A market capitalization below reported cash does not automatically mean the shares are undervalued because the company continues to spend heavily, has liabilities and may need to fund another lengthy development program. It does illustrate how little value investors currently appear willing to assign to TNX-103 after adjusting for expected future cash consumption.

The selloff also reflects how sharply the investment thesis has changed. Before LEVEL, investors could contemplate a successful pivotal readout, regulatory submission and eventual entry into a disease area without a specifically approved therapy. After LEVEL, the path involves an FDA meeting, possible protocol modifications, subgroup validation and another pivotal test whose outcome is uncertain.

The 26.3-meter subgroup finding prevents TNX-103 from becoming an obvious write-off, while the NT-proBNP and right ventricular pressure results offer biological support for continued development. Those signals are valuable precisely because they create a rational next experiment, but they should not be treated as substitutes for the failed Phase 3 outcome.

Tenax Therapeutics still has enough cash to attempt the recovery and enough clinical evidence to justify asking regulators for a revised pathway. The company now needs the FDA to agree that concentrating on patients with greater disease burden is scientifically and statistically defensible, followed by a prospectively successful study proving the benefit can be reproduced.

Until that happens, TNX-103 has moved from a near-term registration opportunity to a high-risk salvage strategy. The market’s nearly 90% repricing reflects that distinction more clearly than any headline biomarker result.

Key takeaways on what the TNX-103 Phase 3 failure means for Tenax Therapeutics

• TNX-103 missed the LEVEL primary endpoint after producing only a 3.5-meter adjusted improvement over placebo in six-minute walk distance, with a p-value of 0.63.
• The key Kansas City Cardiomyopathy Questionnaire symptom endpoint also failed, with only a 0.1-point adjusted difference between TNX-103 and placebo.
• Patients walking less than 333 meters at baseline showed a 26.3-meter placebo-adjusted benefit, giving Tenax Therapeutics a potential enrichment strategy for future trials.
• The subgroup result was prespecified, but it still requires prospective confirmation because the overall Phase 3 trial was negative.
• TNX-103 produced a 49% greater reduction in NT-proBNP and a 3.5-millimeter-of-mercury reduction in right ventricular systolic pressure relative to placebo.
• Tenax Therapeutics plans a Type C meeting with the FDA to discuss changing the ongoing registrational strategy around patients with greater disease severity.
• LEVEL-2 remains underway, but its design and role could change depending on regulatory feedback following the LEVEL failure.
• Tenax Therapeutics had $118 million in cash at June 30 and previously projected funding through the second quarter of 2028.
• Research and development spending more than doubled year over year during the second quarter as the company funded its two Phase 3 studies.
• Tenax Therapeutics shares collapsed nearly 90% on August 10, cutting the company’s market capitalization to roughly $70 million and signaling extremely negative investor sentiment toward the revised approval outlook.