Tortugas Neuroscience Reports Positive Phase 2b Results for Obuprazine in Schizophrenia, Showing Significant Symptom Improvements and Rapid Clinical Response
Tortugas Neuroscience, a clinical-stage biotechnology company focused on developing transformative therapies for central nervous system (CNS) disorders, has announced positive Phase 2b clinical trial results for obuprazine (TRTL-107), its investigational treatment for schizophrenia. The findings, generated in a study conducted by Tortugas’ partner Hansoh Pharma and presented at the 2026 European College of Neuropsychopharmacology (ECNP) Congress, demonstrated statistically significant and clinically meaningful improvements in schizophrenia symptoms across all three obuprazine dose groups compared with placebo.
The Phase 2b results showed improvements in the Positive and Negative Syndrome Scale (PANSS) total score, evidence of a rapid onset of clinical response, and benefits across several symptom domains. The study also reported a generally favorable tolerability profile, with discontinuation rates among obuprazine-treated patients comparable to those observed in the placebo group.
The lowest evaluated dose range, 1.5–3.0 mg, demonstrated the largest treatment effect on the primary endpoint at Day 42. Patients in this group experienced a least-squares mean change of -28.6 points from baseline in PANSS total score, compared with -11.9 points for placebo. This represented a placebo-adjusted difference of -16.7 points, with a reported p-value of less than 0.0001.
The other two obuprazine dose groups also demonstrated statistically significant improvements. The 4.5–6.0 mg group achieved a placebo-adjusted difference of -13.2 points, while the 6.0–9.0 mg group achieved a difference of -14.7 points. Both results had p-values of less than 0.0001.
The findings provide encouraging evidence for the continued development of obuprazine, particularly given the persistent need for treatments that can address the multiple symptom dimensions of schizophrenia while maintaining an acceptable tolerability profile. Tortugas plans to submit a U.S. Investigational New Drug (IND) application for TRTL-107, with detailed results from the Phase 2b study expected to be submitted for publication in a peer-reviewed journal.
Phase 2b Trial Demonstrates Significant Improvements in PANSS Total Score
The primary endpoint of the Phase 2b trial was the change from baseline in PANSS total score at Day 42. PANSS is a standardized clinical assessment used to measure the severity of schizophrenia symptoms, including positive symptoms, negative symptoms and general psychopathology.
Positive symptoms can include hallucinations, delusions and disorganized thinking. Negative symptoms may involve reduced emotional expression, diminished motivation, reduced speech and decreased engagement in everyday activities. General psychopathology encompasses additional clinical features that contribute to the overall burden of schizophrenia.
By evaluating the PANSS total score, researchers can assess changes across a broad range of symptoms rather than focusing on a single manifestation of the disorder.
According to Tortugas, all three obuprazine dose groups achieved statistically significant and clinically meaningful improvements compared with placebo at Day 42.
The 1.5–3.0 mg dose group produced the largest reported treatment effect, with a least-squares mean change from baseline of -28.6 points. The placebo group recorded a mean change of -11.9 points, resulting in a placebo-adjusted difference of -16.7 points.
The 4.5–6.0 mg dose group demonstrated a placebo-adjusted improvement of -13.2 points, while the 6.0–9.0 mg dose group demonstrated a difference of -14.7 points. Both dose groups achieved statistical significance, with p-values below 0.0001.
These findings suggest that obuprazine produced measurable improvements across the evaluated dose ranges. The numerical results also show that the lowest dose range generated the largest placebo-adjusted improvement in the primary endpoint in this study.
However, the results alone do not establish that the lowest dose will be optimal for every patient or that the observed pattern will be reproduced in future trials. Additional clinical research will be required to determine the most appropriate dose range, characterize the consistency of response and establish the medicine’s benefit-risk profile.
The primary endpoint findings nevertheless provide a key basis for advancing the clinical program. The results support further investigation of obuprazine as a potential treatment for adults experiencing acute schizophrenia.
Early Responder Results Suggest a Rapid Onset of Clinical Response
In addition to the Day 42 findings, the study evaluated PANSS responder rates, with a responder defined as a patient achieving a reduction of at least 50% from baseline.
According to Tortugas, the 1.5–3.0 mg and 4.5–6.0 mg dose groups showed a notable increase in responder rates compared with both placebo and aripiprazole as early as Day 14.
The early separation in responder rates is an important observation because the speed of symptom improvement can be clinically relevant in acute schizophrenia, particularly for patients experiencing symptoms severe enough to require hospitalization.
The study enrolled adults with acute schizophrenia who had required hospitalization within two months before screening. In this population, researchers sought to evaluate whether treatment could produce measurable improvements over the six-week assessment period.
The Day 14 responder findings suggest that some patients receiving the two specified dose ranges experienced substantial reductions in symptoms relatively early in treatment. However, the available announcement does not provide exact responder percentages or confidence intervals for these comparisons.
Consequently, the reported findings should be interpreted as encouraging early clinical evidence rather than definitive proof of faster response across all patients. Further details from the complete study report will be important for understanding the magnitude, variability and statistical robustness of the early treatment effects.
The company also reported numerically greater efficacy for obuprazine than for aripiprazole across multiple endpoints, including the primary endpoint. Aripiprazole served as the active-reference treatment in the study, allowing researchers to compare the investigational medicine with an established antipsychotic treatment.
The reported numerical differences are potentially relevant to the future development of obuprazine. However, without detailed comparative statistical analyses, they should not be interpreted as establishing superiority over aripiprazole.
Improvements Observed Across Positive and Negative Symptoms
The Phase 2b results extended beyond the PANSS total score. At Day 42, all three obuprazine dose groups demonstrated statistically significant and clinically meaningful improvements compared with placebo across the PANSS positive symptom subscale, negative symptom subscale and Marder cognitive factor scores.
The positive symptom subscale evaluates symptoms such as hallucinations, delusions and disorganized thought processes. The negative symptom subscale assesses features such as reduced emotional expression, diminished motivation and decreased social engagement.
The Marder cognitive factor is a PANSS-derived grouping of items associated with cognitive and related symptom domains. It provides an additional perspective on changes in clinical features that may affect everyday functioning.
At the 1.5–3.0 mg dose, the placebo-adjusted improvement was 5.3 points on the PANSS positive symptom subscale and 4.4 points on the negative symptom subscale. Both comparisons had p-values below 0.0001.
These findings suggest that the treatment’s observed effects were not confined to one category of schizophrenia symptoms. Instead, the reported improvements extended across several clinically relevant domains.
This breadth of response is important in schizophrenia treatment research because patients can experience a combination of positive symptoms, negative symptoms and other impairments. A treatment that improves multiple symptom domains could potentially address a broader portion of the disease burden, provided those benefits are confirmed in further clinical studies.
Nevertheless, changes in symptom-rating scales do not automatically establish improvements in long-term functioning, independence or quality of life. Additional studies will be needed to assess whether the observed clinical changes translate into sustained benefits for patients in everyday settings.
The company’s results provide a basis for investigating these questions as obuprazine progresses through clinical development.
Study Design Included Placebo and Active-Reference Groups
The randomized, double-blind, placebo- and active-reference-controlled Phase 2b trial enrolled 363 Chinese adults with acute schizophrenia across 24 clinical centers.
Participants had required hospitalization within two months before screening. The study design included five treatment groups:
- Obuprazine at 1.5–3.0 mg.
- Obuprazine at 4.5–6.0 mg.
- Obuprazine at 6.0–9.0 mg.
- Aripiprazole as the active-reference treatment.
- Placebo.
The primary endpoint was the change from baseline in PANSS total score at Day 42.
Randomization helps distribute participant characteristics across treatment groups, while blinding is intended to reduce the influence of expectations on patient assessments and investigator judgments. Including both placebo and an active-reference treatment also allows researchers to assess the investigational treatment against different comparators.
The study’s 42-day primary assessment provided a defined period for evaluating changes in symptoms following treatment. The additional responder analyses at Day 14 offered information about the timing of observed improvement, while the subscale assessments helped characterize the breadth of the treatment response.
The trial’s results were presented at the 2026 ECNP Congress. Tortugas said detailed findings are expected to be submitted to a peer-reviewed journal, where additional information about the study methodology, statistical analyses, safety results and limitations can be evaluated.
Although the reported outcomes are positive, the study population and duration are important considerations when interpreting the findings. The trial involved Chinese adults with acute schizophrenia, and further studies will be needed to characterize the medicine’s performance across broader populations and longer treatment periods.
Obuprazine Demonstrates a Generally Favorable Tolerability Profile
Alongside the efficacy findings, Tortugas reported that obuprazine was generally well tolerated in the Phase 2b trial.
Treatment discontinuation rates were comparable between obuprazine-treated patients and the placebo group. The reported discontinuation rate was 2.5% for placebo and approximately 2.1% among patients receiving obuprazine.
These figures suggest that discontinuation was uncommon during the study and occurred at a similar rate in the treatment and placebo groups. However, discontinuation rates alone do not provide a complete assessment of safety. A comprehensive evaluation also requires information about adverse events, their severity, their relationship to treatment and any clinically significant changes identified during monitoring.
The company has characterized the overall tolerability profile as favorable, but the full safety dataset will be important for determining the treatment’s benefit-risk balance.
Safety is a central consideration in schizophrenia treatment because patients may require ongoing management over extended periods. A candidate medicine must therefore be evaluated not only for its ability to reduce symptoms but also for the tolerability of treatment at doses likely to provide meaningful clinical benefit.
Tortugas believes obuprazine’s pharmacological profile may support broad symptom control while potentially addressing certain tolerability limitations. That hypothesis will require further evaluation through additional clinical studies.
Tortugas Highlights Obuprazine’s Potentially Differentiated Pharmacology
Jeff Jonas, Chief Executive Officer of Tortugas Neuroscience, described the Phase 2b results as a significant milestone for the company’s schizophrenia program.
“These Phase 2b trial results represent one of the most compelling efficacy datasets reported in schizophrenia in recent years and provide strong evidence for the potential of obuprazine to deliver clinically meaningful efficacy across symptom domains, with an early onset of clinical response,” Jonas said.
He added: “We believe the consistency and breadth of these results position obuprazine as a potentially differentiated treatment option in a market with significant unmet need. These data represent a major milestone for Tortugas and strengthen our confidence as we advance the program toward the next stage of development.”
The company’s assessment reflects the reported improvements in PANSS total score, the early responder findings and the changes observed across multiple symptom domains. These outcomes form the basis for Tortugas’ view that obuprazine could offer a differentiated option if the findings are confirmed in subsequent studies.
Al Robichaud, Ph.D., President and Head of Research and Development at Tortugas, highlighted the investigational medicine’s receptor activity as a potential explanation for its observed effects.
“We believe that obuprazine’s differentiated pharmacology, including its functional modulation of dopamine D2, D3, and 5-HT1A receptors, coupled with potent antagonism of serotonin 5-HT2A receptors, may support broad control across multiple symptom domains while potentially addressing tolerability limitations,” Robichaud said.
He continued: “Importantly, the Phase 2b results are consistent with this pharmacologic profile, with obuprazine demonstrating robust results across multiple symptom domains and a favorable tolerability profile. We are particularly encouraged by the results observed across dose levels, which may provide physicians flexibility to optimize treatment based on individual patient needs.”
The receptor activity described by Robichaud is relevant to the biological systems involved in schizophrenia and the pharmacological actions of antipsychotic medicines. Dopamine and serotonin signaling pathways have established roles in neuropsychiatric research, and medicines that interact with these systems are investigated for their potential effects on psychotic symptoms and other clinical features.
However, the precise contribution of each receptor interaction to obuprazine’s clinical results has not been established by the reported trial findings. Further research will be required to determine how the pharmacological profile relates to efficacy, tolerability and dose selection.
Development Plans Include a U.S. IND Application
Following the positive Phase 2b findings, Tortugas plans to submit a U.S. Investigational New Drug application for TRTL-107.
An IND application is a regulatory submission that seeks authorization to investigate an investigational medicine in human clinical studies in the United States. Submission of an IND is an important step in establishing the regulatory pathway for clinical development, but it does not mean that a treatment has been approved for marketing.
Tortugas has not provided further details in the announcement about the timing of the planned submission or the design of the next clinical study.
The company also expects detailed results from the Phase 2b trial to be submitted for publication in a peer-reviewed journal. Publication would allow the broader scientific and medical communities to examine the findings in greater detail, including the study design, efficacy analyses, safety outcomes and limitations.
Additional data will be important for understanding the consistency of the treatment effects, evaluating the reported differences among dose groups and determining the extent to which the findings support further development.
Positive Results Advance Tortugas’ Schizophrenia Program
The Phase 2b results represent an important development milestone for Tortugas Neuroscience as it advances obuprazine toward the next stage of clinical development.
Across all three evaluated dose groups, the investigational treatment produced statistically significant improvements in PANSS total score compared with placebo at Day 42. The 1.5–3.0 mg group demonstrated the largest placebo-adjusted improvement, while the 1.5–3.0 mg and 4.5–6.0 mg groups also showed higher responder rates than placebo and aripiprazole as early as Day 14.
The study further reported improvements across positive symptoms, negative symptoms and Marder cognitive factor scores, together with discontinuation rates comparable to placebo.
These findings support continued investigation of obuprazine as a potential treatment for schizophrenia, a condition in which patients may experience complex symptoms that affect perception, thinking, motivation and daily functioning.
The next phase of development will need to establish whether the reported efficacy and tolerability findings can be replicated, clarify the most appropriate dose range and provide additional information about longer-term safety and clinical benefit.
With plans to submit a U.S. IND application and prepare the full Phase 2b findings for peer-reviewed publication, Tortugas is moving toward further evaluation of TRTL-107. While the investigational medicine has not been established as an approved treatment, the reported results provide a clinical foundation for continued research into its potential role in schizophrenia care.
About Obuprazine (TRTL-107)
Obuprazine (or TRTL-107), Tortugas’ most advanced product candidate, is a dopamine D2/D3 receptor partial agonist, 5-HT2A receptor antagonist and 5-HT1A receptor partial agonist for the treatment of schizophrenia. Tortugas holds global commercial development rights for obuprazine, excluding Greater China. Hansoh Pharma has successfully completed multiple clinical trials for obuprazine to date, including this recent Phase 2b trial.
Despite the availability of multiple antipsychotic therapies, many patients continue to experience persistent symptoms, inadequate response, treatment discontinuation, and functional impairment, underscoring the need for new treatments that can deliver broad symptom control while maintaining favorable tolerability. The efficacy and tolerability profile demonstrated in this study support the potential for obuprazine to become a differentiated treatment option for patients living with schizophrenia.
About Tortugas Neuroscience
Tortugas Neuroscience is a clinical-stage CNS-focused biotech company dedicated to developing medicines that address diseases of the brain. With a strategic focus on clinically validated mechanisms of action with well-defined development and regulatory pathways, Tortugas Neuroscience is committed to creating therapies with meaningful impact for patients worldwide.