Pasithea Therapeutics Announces Positive PAS-004 Clinical Data from Phase 1 Advanced Cancer Study Presented at ESMO Congress 2026
Two patients remained on PAS-004 beyond 500 days with prolonged stable disease after prior targeted combination therapy failed.
Sentiment and the balance of points
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Rhea-AI Summary
Pasithea Therapeutics (Nasdaq: KTTA) reported updated Phase 1 PAS-004 cancer study data showing prolonged stable disease and preliminary safety findings. Results presented at ESMO Congress 2026 reflect 37 patients across 10 dose cohorts as of September 15, 2026, in an ongoing dose-escalation study of advanced solid tumors.
Four patients had received PAS-004 for more than 300 days; two remained on treatment beyond 500 days with prolonged stable disease. Treatment-related adverse events affected 45.9% (17 of 37), all Grade 1 or 2. No dose-limiting toxicities, treatment-related discontinuations, or MEK inhibitor-associated heart or retinal toxicities were observed. The maximum tolerated dose had not been reached. Estimated half-life was approximately 58 hours, with a peak-to-trough drug concentration ratio below 1.5 at steady state; the company said this supports long-term, once-daily dosing.
Positive
- Minor pointFour patients received PAS-004 for more than 300 days with prolonged stable disease.
- Minor pointTwo patients remained on treatment beyond 500 days despite prior dabrafenib/trametinib progression in BRAF V600E-mutant melanoma.
- Minor pointNo dose-limiting toxicities were observed; the maximum tolerated dose had not been reached.
- Minor pointNo treatment-related discontinuations or related serious adverse events were reported.
- Minor pointNo MEK inhibitor-associated cardiac or retinal toxicities were observed to date.
2 minor points
- Minor point. Forward-looking: it has not happened yet and may not happen.Approximately 58-hour half-life and peak-to-trough ratio below 1.5 support chronic once-daily dosing, the company said.
- Minor pointDrug exposure increased proportionally with dose in the dose-escalation study.
Negative
- Minor pointTreatment-related adverse events affected 45.9% (17 of 37) patients; all were Grade 1 or 2.
- Minor pointNausea 14%, vomiting 11%, rash 11%, increased blood creatine phosphokinase 11%, diarrhea 5% were the most common treatment-related events.
Details
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Key Figures
- Prolonged stable disease
- 4 patients for >300 days
- PAS-004 advanced-cancer study
- Ongoing treatment
- 2 patients for >500 days
- Patients with prolonged stable disease
- Enrollment
- 37 patients
- Phase 1 dose-escalation study
- Treatment-related adverse events
- 45.9% (17 of 37); all Grade 1 or 2
- Reported in the Phase 1 study
- Grade ≥3 events
- 0
- No Grade ≥3 events observed
- Treatment-related discontinuations
- 0
- No patients discontinued due to treatment-related adverse events
- Half-life
- ~58 hours
- PAS-004 pharmacokinetics
- Cmax/Cmin ratio
- <1.5
- At steady state
Previous Clinical trial Reports
-
Prior interim Phase 1 results reported durable disease stabilization and favorable safety in heavily pre-treated advanced-cancer patients.
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Key Terms
dose-limiting toxicities medical
maximum tolerated dose medical
pharmacokinetics medical
cmax/cmin technical
auc medical
AI-generated analysis. How Rhea-AI works. Not financial advice.
-- Prolonged Stable Disease: PAS-004 achieved prolonged stable disease in a heavily pre-treated population, with four patients on PAS-004 for more than 300 days, including two who continue on once daily PAS-004 for over 500 days despite recurrent, metastatic melanoma carrying the BRAF V600E mutation and prior progression on targeted combination therapy with dabrafenib and trametinib.
-- Long-Term Tolerability: Overall, the safety profile of PAS-004 in the heavily pre-treated advanced cancer population appears favorable. No Grade 3 treatment-related adverse events (“AEs”), no discontinuations due to treatment-related AEs, and no related serious AEs have been reported. Treatment-related AEs remain low-grade and manageable, with low rates of vomiting, nausea, diarrhea, and rash, including none reported by the four patients on-study for >300 days. None of the MEKi class effects on the heart or the retina have been reported. To date, there have been no dose-limiting toxicities, and the maximum tolerated dose has not been reached.
-- Favorable Pharmacokinetic Profile: PAS-004 demonstrated a long half-life, approximately 58 hours on average, with a low Cmax/Cmin ratio of less than 1.5. AUC increased proportionally in this dose escalation study. The flat pharmacokinetic curve with a long half-life supports long-term, chronic dosing.
MIAMI, Oct. 23, 2026 (GLOBE NEWSWIRE) -- Pasithea Therapeutics Corp. (Nasdaq: KTTA) (“Pasithea” or the “Company”), a clinical-stage biotechnology company developing PAS-004, a next-generation macrocyclic oral MEK inhibitor, today announced updated safety, tolerability, and preliminary efficacy data from its ongoing Phase 1 dose-escalation study of PAS-004 monotherapy in a heavily pre-treated population of patients with MAPK pathway-driven advanced solid tumors harboring RAS, NF1 or RAF mutations, including patients who have failed prior BRAF/MEK inhibitor treatment (NCT06299839). The data, reflecting durable clinical benefit, including prolonged stable disease in four patients, as well as long-term tolerability and flat pharmacokinetics, are being presented today at the ESMO Congress 2026, taking place October 23-27, 2026, in Madrid, Spain.
“The prolonged stable disease that we’re seeing in some patients across this heavily pre-treated population is highly encouraging, particularly in patients with BRAF V600E-mutant tumors who previously progressed on BRAFi monotherapy and/or BRAFi/MEKi combination therapy. The literature reports a median progression-free survival of approximately five months for combination BRAFi/MEKi rechallenge in this setting, and some patients in the BRAF-mutant subgroup are exceeding that benchmark with our MEKi monotherapy,” said Dr. Kartik Krishnan, Chief Medical Officer of Pasithea. “What makes this data especially encouraging is that we’re seeing these signals of durable clinical benefit alongside a long-term tolerability profile that continues to hold up. No patient has discontinued treatment at any dose level due to treatment-related adverse events, and we continue to observe low rates of vomiting and other GI toxicity, low rates of rash, even in patients taking PAS-004 continuously for long periods of time. A tolerability profile like this is exactly what you want to see for the long-term treatment of chronic diseases including neurofibromatosis type 1 (NF1).”
Details of the Presentation:
Title: Phase I Dose-Escalation Study of the Safety and Pharmacokinetics of PAS-004, a Macrocyclic MEK Inhibitor, for the Treatment of Patients with MAPK Pathway Driven Advanced Solid Tumors
Abstract/Poster Number: 1050P
Session: Developmental Therapeutics
Date/Time: Friday, October 23, 2026, 15:15–16:00 CEST
Key Findings (Data as of 15 September 2026):
Enrollment: 37 patients enrolled in dose escalation across 10 dose cohorts (2mg, 4mg, 8mg, 15mg, 22mg, 30mg, 37mg and 45mg capsule formulations, and 4mg and 18mg tablet formulations).
Patient Population: Heavily pre-treated population with a median of 3 prior lines of therapy (range 1–8); median age 57 years;
BRAF-Mutant Patients: 12 patients enrolled with BRAF V600E mutations, 10 of whom previously progressed on BRAF and/or BRAF/MEK combination therapy.
Prolonged Stable Disease: Four patients have been on PAS-004 for greater than 300 days; two patients remain on treatment for more than 500 days with prolonged stable disease.
Safety: No dose limiting toxicities were observed. No patient has discontinued PAS-004 due to treatment-related adverse events (TRAEs). No grade ≥3 were observed. TRAEs reported in
Pharmacokinetics: Linear PK with an estimated half-life of ~58 hours and a flat Cmax/Cmin ratio below 1.5 at steady state, supporting long term, once-daily (QD) dosing.
About Pasithea Therapeutics Corp.
Pasithea is a clinical-stage biotechnology company primarily focused on the research and development of its lead drug candidate, PAS-004, a next-generation macrocyclic MEK inhibitor intended for the treatment of RASopathies, MAPK pathway-driven tumors, and other diseases. The Company is currently testing PAS-004 in a Phase 1 clinical trial in advanced cancer patients (NCT06299839), and a Phase 1/1b clinical trial in adult patients with neurofibromatosis type 1 (NF1)-associated plexiform neurofibromas (NCT06961565).
Forward Looking Statements
This press release contains statements that constitute “forward-looking statements” made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. These forward-looking statements include statements regarding the Company’s clinical data from its ongoing Phase 1 dose-escalation study of PAS-004 in advanced solid tumors, , the Company’s ongoing Phase 1/1b clinical trial of PAS-004 in adult NF1 patients, and the safety, tolerability, pharmacokinetic (PK), pharmacodynamic (PD) and preliminary efficacy of PAS-004, as well as all other statements, other than statements of historical fact, regarding the Company’s current views and assumptions with respect to future events regarding its business, as well as other statements with respect to the Company’s plans, assumptions, expectations, beliefs and objectives, the success of the Company’s current and future business strategies, product development, pre-clinical studies, clinical studies, clinical and regulatory timelines, market opportunity, competitive position, business strategies, potential growth and financing opportunities and other statements that are predictive in nature. Forward-looking statements are subject to numerous conditions, many of which are beyond the control of the Company. While the Company believes these forward-looking statements are reasonable, undue reliance should not be placed on any such forward-looking statements, which are based on information available to the Company on the date of this release. These forward-looking statements are based upon current estimates and assumptions and are subject to various risks and uncertainties, including risks that future clinical trial results may not match results observed to date, may be negative or ambiguous, or may not reach the level of statistical significance required for regulatory approval, as well as other factors set forth in the Company’s most recent Annual Report on Form 10-K, Quarterly Report on Form 10-Q and other filings made with the U.S. Securities and Exchange Commission (SEC). Thus, actual results could be materially different. The Company undertakes no obligation to update these statements whether as a result of new information, future events or otherwise, after the date of this release, except as required by law.
Contact
Patrick Gaynes
Investor Relations
pgaynes@pasithea.com
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
What did Pasithea's Phase 1 PAS-004 cancer study show about stable disease?
Four patients had prolonged stable disease while receiving PAS-004 for more than 300 days, including two remaining on treatment beyond 500 days. Those two patients had recurrent, metastatic BRAF V600E-mutant melanoma and had previously progressed on dabrafenib plus trametinib.
What safety results did Pasithea report for PAS-004?
Treatment-related adverse events occurred in 45.9% (17 of 37) patients and were all Grade 1 or 2. No dose-limiting toxicities, treatment-related discontinuations, or related serious adverse events were reported. No MEK inhibitor-associated effects on cardiac function or the retina were observed to date.
Which patients were enrolled in Pasithea's PAS-004 Phase 1 cancer study?
The study enrolled patients with MAPK pathway-driven advanced solid tumors carrying RAS, NF1 or RAF mutations, including patients whose prior BRAF/MEK inhibitor treatment had failed. Patients had a median of 3 prior treatment lines, ranging from 1–8. Of 12 patients with BRAF V600E mutations, 10 had previously progressed on BRAF and/or BRAF/MEK combination therapy.