On November 20, 2025 Pasithea Therapeutics Corp. (Nasdaq: KTTA) ("Pasithea" or the "Company"), a clinical-stage biotechnology company developing PAS-004, a next-generation macrocyclic oral MEK inhibitor for the treatment of neurofibromatosis type 1-associated plexiform neurofibromas (NF1-PN), reported positive interim Phase 1 data from its ongoing first-in-human trial evaluating PAS-004 in patients with MAPK pathway-driven advanced solid tumors with a documented RAS, NF1 or RAF mutation, or in patients who have failed prior BRAF/MEK inhibition.

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Dr. Tiago Reis Marques, CEO of Pasithea said, "Today’s updated interim results from our advanced cancer trial demonstrate the safety, PK and anti-tumor activity of PAS-004, and support its potential to be a best-in-class MEK inhibitor for the treatment of NF1-PN. Achieving a monotherapy partial response in an advanced cancer patient who had previously received a MEK + BRAF inhibitor combination therapy, and whose prior best response had been stable disease, is very promising. At our highest reported cohort (30mg capsule), we are seeing significant drug exposures (Area Under the Curve (AUC) greater than 5,400 ng·h/mL), with a relatively flat PK curve, suggesting sustained pathway inhibition. We believe this profile is well aligned with what is needed to drive meaningful clinical responses in NF1-PN patients. Published clinical data has shown that tumor response in NF1-PN is positively correlated with drug exposure (AUC), reinforcing the relevance of these findings."

Dr. Rebecca Brown, Director of the Neurofibromatosis (NF) and Schwannomatosis (SWN) Program at University of Alabama Birmingham (UAB) and Scientific Advisory Board member of Pasithea, stated: "I find it very encouraging that even when used as a monotherapy in advanced recurrent cancer patients, PAS-004 has demonstrated early signals of efficacy, but more importantly exhibited such a favorable safety profile that no dose interruptions or modifications were required. Maintaining NF1-PN patients on treatment for extended periods of time is paramount to achieving maximum tumor control. I believe that PAS-004’s early efficacy signals combined with the low rate of adverse side effects may translate into better tolerability and longer time-on-treatment for plexiform neurofibromas associated with NF1, compared with current FDA-approved therapies discontinuation rates estimated as high as 40-50% before year two."

Interim Phase 1 Results for PAS-004:

Initial Signals of Clinical Activity

Among 21 efficacy evaluable patients (as per RECIST1.1):

Partial Response:
A BRAF V600E melanoma patient in Cohort 4A (15mg capsule) achieved an unconfirmed partial response with a –31.9% tumor reduction and remains on trial for >11 months; prior best response when treated with a MEK + BRAF combination therapy was stable disease
Disease Control Rate (DCR):
71.4% (5 of 7) of patients identified with BRAF-mutated tumors achieved stable disease or partial response
42.8% (9 of 21) of patients achieved stable disease or partial response
Durable Stable Disease:
A second BRAF V600E melanoma patient previously treated with MEK + BRAF combination therapy in Cohort 6 (30mg capsule) remains on trial for >6 months with a stable disease and tumor shrinkage of -1.6%
Safety and Tolerability

Among 27 dosed patients through the Dose Limiting Toxicity (DLT) period (Day 28) through the cutoff date of November 10, 2025:

PAS-004, dosed once daily (QD), has been well-tolerated across all dose levels
No dose-limiting toxicities (DLTs), and no discontinuations have been reported.
All treatment-related adverse events (TRAEs) at least possible related to PAS-004 were Grade 1 or 2, with limited rash (7.4%), nausea (18.5%), vomiting (14.8%), diarrhea (7.4%), and no ocular retinal abnormalities or cardiovascular toxicities observed.
Pharmacokinetics (PK)

PAS-004 has demonstrated through Cohort 6:

Linear PK and dose-proportionality
PK curve with Cmax/Cmin ratio <2, with Cmax and Cmin above the IC50 (half-maximal inhibitory concentration) from our cellular assay.
Long half-life (~60 hours)
Cohort 6 (30mg capsule) has demonstrated:
AUC: ~5,480 ng·h/mL
Cmax: 249 ng/mL
Cmin: 215 ng/mL

(Press release, Pasithea Therapeutics, NOV 20, 2025, View Source [SID1234660849])