Pasithea Therapeutics Presents Positive Initial Phase 1/1b Data for PAS-004, Showing Substantial Reductions in Cutaneous Neurofibroma Size and Early Activity in Plexiform Neurofibromas at the 2026 European Neurofibromatosis Conference

Rhea-AI Summary

Pasithea Therapeutics (KTTA) reported initial Phase 1/1b PAS-004 data showing a median best reduction of 41% in target skin-tumor surface area. All 15 evaluable participants with cutaneous neurofibromas (cNF) showed reductions; the median best reduction was 46% at doses planned for Phase 2. Among participants followed through 12 cycles, the median reduction reached 49%; the 4mg cohort reached 71% at Cycle 15.

All 18 evaluable participants with plexiform neurofibromas showed tumor-volume reductions. Two met the partial-response threshold; one response awaits confirmation. No treatment-related serious adverse events or discontinuations occurred, but two Grade 3 muscle-enzyme increases required temporary dosing interruptions. The FDA cleared the investigational new drug application for a placebo-controlled Phase 2 cNF trial in approximately 200 adults. The ongoing study is open-label.

16 points · 0 major

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Hollow bars mark forward-looking points. How the balance works

Positive

• Moderate pointTarget cNF surface area decreased in all 15 evaluable participants, with a median best reduction of 41%.
• Moderate pointTarget plexiform-neurofibroma volume decreased in all 18 evaluable participants by blinded independent review.
• Moderate pointThe FDA cleared the Phase 2 cNF investigational new drug application for approximately 200 adults.
• Moderate point. Forward-looking: it has not happened yet and may not happen.Pasithea plans a randomized, double-blind, placebo-controlled Phase 2 trial evaluating three once-daily doses.
• Minor pointPlanned Phase 2 doses of 4, 8 and 12mg produced a 46% median best cNF surface-area reduction.

11 minor points

• Minor pointThe six participants at 4mg and 8mg each achieved cNF surface-area reductions greater than 40%.
• Minor pointMedian cNF surface-area reduction deepened from 12% at Cycle 1 to 49% at Cycle 12 among participants followed through 12 cycles.
• Minor pointThe 4mg cohort reached a median cNF surface-area reduction of 71% at Cycle 15.
• Minor pointTarget cNF longest diameter decreased at least 25% in 27 of 37 lesions (73%) at planned Phase 2 doses.
• Minor pointNon-resected cNFs met the diameter-shrinkage criterion in 24 of 29 lesions (83%); median best reduction was 39%.
• Minor pointTwo participants at 12mg and 15mg met the plexiform-neurofibroma partial-response threshold.
• Minor pointSafety findings included no treatment-related serious adverse events or discontinuations, retinopathy, or decreased left ventricular ejection fraction.
• Minor pointTreatment-related adverse events were Grade 1 or 2 in 97.6% of events.
• Minor pointPAS-004 showed a 40-to-60-hour half-life and approximately dose-proportional exposure across 4 to 24mg.
• Minor point. Forward-looking: it has not happened yet and may not happen.The ongoing Phase 1/1b study will continue follow-up and advance toward randomized two-dose expansion.
• Minor point. Forward-looking: it has not happened yet and may not happen.Pasithea expects to complete analyses of drug effects in surgically removed cNFs in 2027.

Negative

• Minor pointInitial findings come from an ongoing, open-label Phase 1/1b study with 19 participants enrolled as of September 15, 2026.
• Minor pointThe 15mg participant's 22.5% tumor-volume reduction at Cycle 4 remains pending confirmation on a subsequent scan.
• Minor pointTwo Grade 3 blood creatine phosphokinase increases required one-week dose interruptions; both resolved and participants continued treatment.
• Minor pointAt planned Phase 2 doses, rash and diarrhea occurred in 33% and 11% of participants, respectively.
• Minor pointcNF assessment has no regulatory standard; results used surface-area and longest-diameter measurements.

Key Figures

Median best cNF surface-area reduction: 41% Median best cNF surface-area reduction: 46% Median cNF surface-area reduction: 49% +5 more

Median best cNF surface-area reduction

41%

Across all doses; 15 evaluable participants

Median best cNF surface-area reduction

46%

Among eight evaluable participants at the planned Phase 2 doses

Median cNF surface-area reduction

49%

At Cycle 12 among participants followed through 12 cycles

Median cNF surface-area reduction

71%

At Cycle 15 in the 4mg cohort

Target PN volume reduction

22.5%

One participant at the first on-treatment MRI; pending confirmation

Target cNFs meeting longest-diameter reduction criterion

27 of 37 (73%)

At 4, 8 and 12mg; reduction of at least 25%

Grade 1 or 2 treatment-related adverse events

97.6% of events

Reported in the ongoing study

Planned Phase 2 trial enrollment

Approximately 200 adults

FDA-cleared trial evaluating three once-daily doses

Previous Clinical trial Reports

2 past events · Latest: Nov 03

Same Type 2 events

1. Nov 03

   IND clearance

   24h Move

   +44.0%

   FDA cleared a Phase 2 trial of PAS-004 for NF1-associated cutaneous neurofibromas.

2. Oct 23

   Phase 1 data

   24h Move

   -9.1%

   Advanced-cancer data reported prolonged stable disease and preliminary safety findings for PAS-004.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

pharmacokinetics, lvef, open-label, placebo-controlled

4 terms

pharmacokinetics medical

"The study also assesses safety, tolerability, pharmacokinetics and pharmacodynamics."

Pharmacokinetics is the study of how a substance, such as a drug or chemical, moves through and is processed by the body over time. It tracks how it is absorbed, distributed, broken down, and eventually eliminated. For investors, understanding pharmacokinetics helps gauge the effectiveness, safety, and potential risks of new medications or treatments, which can influence a company’s success and valuation in the healthcare industry.

lvef medical

"adverse event of decreased left ventricular ejection fraction (LVEF)"

Left ventricular ejection fraction (LVEF) is a percentage that measures how much blood the heart’s main pumping chamber pushes out with each beat, like the share of water a pump empties from a bucket each cycle. Investors watch LVEF because it’s a key medical yardstick used to diagnose and track heart function, shaping demand for drugs, devices, clinical trials, insurance costs and the financial outlook of healthcare-related businesses.

open-label technical

"an ongoing multicenter, open-label Phase 1/1b trial"

Open-label describes a situation where everyone involved in a study or process knows the full details, such as who is receiving a treatment or intervention. For investors, understanding whether a project or product is open-label helps gauge the level of transparency and potential biases, influencing trust and decision-making. It’s like knowing whether a test or experiment is conducted openly or behind closed doors.

placebo-controlled technical

"a randomized, double-blind, placebo-controlled Phase 2 trial"

"Placebo-controlled" describes a testing method where one group receives the actual treatment or intervention, while another group receives a harmless, inactive version called a placebo. This approach helps determine whether the real treatment has genuine effects beyond psychological expectations. For investors, understanding this ensures confidence that reported benefits are real and not influenced by bias or false perceptions.

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• All participants showed cutaneous neurofibroma (cNF) reductions: All 15 evaluable participants had reductions in target cNF surface area, with a median best reduction of 41% across all doses and 46% at doses planned for Phase 2
  
  
• cNF reductions deepened with continued treatment: The median reduction in target cNF surface area reached 49% at Cycle 12 among participants followed through 12 cycles and 71% at Cycle 15 in the 4mg cohort
  
  
• Favorable safety and tolerability profile: No treatment related serious adverse events, treatment related discontinuations, retinopathy or adverse event of decreased left ventricular ejection fraction (LVEF)
  
  
• IND cleared for Phase 2 in cNF: The FDA's Division of Dermatology and Dentistry has cleared the IND for a Phase 2 trial of PAS-004 in adults with NF1-associated cNF
  
  
• Early activity in plexiform neurofibromas (PN): Reductions in target PN volume observed in all 18 evaluable participants, including two with reductions ≥20%, one achieving a 22.5% reduction at the first on-treatment MRI (Cycle 4)
  
  
• PAS-004 Clinical Data Webcast: Pasithea will post a webcast on Friday, November 13, 2026, at 7:00 a.m. EST to discuss the data presented at the European Neurofibromatosis Conference
  

MIAMI, Nov. 13, 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 positive clinical data from its ongoing Phase 1/1b study in adults with neurofibromatosis type 1 (NF1)-associated plexiform neurofibromas (PN) and a subset of patients with cutaneous neurofibromas (cNF) (Study PAS-004-103, NCT06961565), presented at the 2026 European Neurofibromatosis Conference in Vienna, Austria.

“Cutaneous neurofibromas do not regress spontaneously and generally increase in number and size with age. The substantial reductions in cNF size reported today represent an encouraging clinical signal in a condition for which there are currently no FDA-approved systemic treatments,” said Dr. Tiago Reis Marques, Chief Executive Officer of Pasithea. “Importantly, these reductions have continued to deepen with longer treatment, including at the lowest doses tested. With our IND now cleared by FDA’s Division of Dermatology and Dentistry, these findings reinforce our confidence in the 4mg to 12mg dose range planned for Phase 2 and support advancing PAS-004 into a randomized, placebo-controlled study in cNF.”

“The reductions in cNF size observed with oral PAS-004 highlight its potential to provide broad, visible improvements for patients through a systemic treatment approach, rather than relying on local procedures that can treat individual lesions,” said Dr. Kartik Krishnan, Chief Medical Officer of Pasithea. “We are also seeing early activity in plexiform neurofibromas, with reductions in tumor volume across all dose levels and two participants meeting the REiNS threshold for partial response, including one at the first on-treatment MRI. Together with the favorable tolerability observed to date and a pharmacokinetic profile characterized by a 40-to-60-hour half-life and limited peak-to-trough fluctuations, these findings support the continued development of PAS-004 as a once-daily oral therapy for long-term treatment of NF1-associated neurofibromas.”

Pasithea will post a webcast on Friday, November 13, 2026, at 7:00 a.m. EST to discuss the PAS-004 clinical data presented at the 2026 European Neurofibromatosis Conference. The webcast will be accessible here and through the Investors section of the Company's website.

Study Overview

Study PAS-004-103 is an ongoing multicenter, open-label Phase 1/1b trial in adults with NF1 and symptomatic and inoperable, incompletely resected, or recurrent PN at five sites in the United States, Australia and South Korea. The study also evaluates up to 7 cNFs in participants with measurable lesions. Part A studies six escalating doses using a 3+3 design to select two doses for evaluation in Part B, a randomized dose expansion phase. The study also assesses safety, tolerability, pharmacokinetics and pharmacodynamics.

As of September 15, 2026, 19 participants have been enrolled across six cohorts (4, 8, 12, 15, 18 and 24mg). Of these, 15 were evaluable for cNF and 18 for PN response. Median treatment duration ranged from 14.4 months at 4mg to approximately 4 months at 15mg and 24mg. One participant discontinued by sponsor decision for noncompliance, unrelated to safety.

Cutaneous Neurofibroma (cNF) Data

Fifteen participants were evaluable for cNF, with 71 target cNFs measured at baseline. Length and width of each target cNF were measured in triplicate with digital calipers. As there is no regulatory standard for assessing cNFs, both surface area (calculated from length and width) and longest diameter (the REiNS-recommended caliper measure) are reported.

Substantial Reductions in cNF Surface Area (Figure 1)

Reductions Across All Doses: All 15 evaluable participants showed reductions in summed target cNF surface area at best response, with a median best reduction of 41%.

Activity at Planned Phase 2 Doses: Among eight evaluable participants treated at 4, 8 and 12mg, the median best reduction was 46%. All six participants treated at 4mg and 8mg achieved reductions greater than 40%.

Figure 1: Best change from baseline in summed target cNF surface area by participant, grouped by dose cohort (N = 15). Data cut-off October 7, 2026.

cNF Reductions Deepened with Continued Treatment (Figure 2)

Among participants followed through 12 treatment cycles, the median reduction in summed target cNF surface area increased from 12% at Cycle 1 to 38% at Cycle 4 and 49% at Cycle 12. In the 4mg cohort, the median reduction reached 71% at Cycle 15.

Figure 2. Change in summed target cNF surface area over time by participant and dose cohort. Dashed lines indicate 20% and 37% reduction thresholds (37% area ≈ 50% volume). Data cut-off: October 7, 2026.

Consistent Findings Using Longest-Diameter Measurements (Figure 3)

At the 4, 8 and 12mg doses planned for the Phase 2 trial, 27 of 37 target cNFs (73%) were reduced by at least 25% in longest diameter, meeting the REiNS shrinkage criterion. Eight of the 37 target cNFs were surgically resected (red ovals) for pharmacodynamic analysis at either Cycle 1 or Cycle 6 and could not be assessed thereafter; they are included with their last measurement before resection. Among the 29 cNFs that were not resected, 24 (83%) met the REiNS criterion, with a median best reduction in longest diameter of 39%.

Figure 3. Best change in target cNF longest diameter at 4, 8 and 12mg (37 target cNF from 8 participants). Red ovals identify the target cNF resected for pharmacodynamic analysis; dashed line indicates the REiNS 25% shrinkage threshold. Data cut-off: October 7, 2026.

Early Activity in Plexiform Neurofibromas (Figure 4)

All 18 evaluable participants showed reductions in target PN volume by blinded independent central review, including two who met the REiNS partial-response threshold at 12mg and 15mg. The 15mg participant achieved a 22.5% reduction at the first on-treatment MRI, pending confirmation on a subsequent scan.

Figure 4. Best change in target PN volume by participant and dose cohort, based on blinded independent central review (N = 18). Dashed line indicates the REiNS 20% partial-response threshold. MRI data cut-off September 30, 2026.

Safety and Tolerability

No treatment-related serious adverse events, discontinuations, adverse events of decreased LVEF, or cases of retinopathy have been reported. Most treatment-related adverse events were Grade 1 or 2 (97.6% of events). The two Grade 3 treatment-related events were asymptomatic increases in blood creatine phosphokinase (CPK), both of which resolved following a one-week dose interruption, with both participants continuing treatment. At the 4 to 12mg doses planned for Phase 2, dermatitis acneiform (rash) and diarrhea occurred in 33% and 11% of participants, respectively (data cut-off: September 15, 2026).

Pharmacokinetics

PAS-004 showed approximately dose-proportional exposure across the 4 to 24mg range, a terminal half-life of 40 to 60 hours, and limited peak-to-trough fluctuations (Cmax/Cmin of 1.5 to 2.0), consistent with findings from the Company's ongoing Phase 1 study in advanced solid tumors and supporting once-daily dosing (data cut-off: October 7, 2026).

Next Steps

The FDA’s Division of Dermatology and Dentistry has cleared the IND for Study PAS-004-201, a randomized, double-blind, placebo-controlled Phase 2 trial evaluating three once-daily doses of PAS-004 in approximately 200 adults with NF1-associated cNF.

The ongoing Phase 1/1b study (PAS-004-103) will continue participant follow-up and advance toward Part B, a randomized two-dose expansion phase. The Company expects to complete pharmacodynamic analyses of resected cNFs in 2027 and present additional clinical data at future scientific meetings.

About Cutaneous Neurofibromas (cNF)

NF1-associated cutaneous neurofibromas (cNFs) are benign tumors that grow in or just beneath the skin at virtually any location in the body and are a hallmark of NF1. It is a serious condition and cNFs are associated with significant morbidity that can have substantial impact on day-to-day functioning, leading patients to rate this as the most significant burden of NF1 despite other potentially life-threatening complications. cNF typically begin to appear in adolescence, generally increase in number and volume with age. The number of cNFs on an individual patient can range from a few to thousands. Although malignant transformation does not occur with NF1-associated cNF, cNFs are present in over 95% of individuals with NF1 and have a significant negative impact both physically, with disfigurement, and on health-related quality of life. Current management relies largely on procedural approaches such as surgical excision, electrodesiccation, or laser therapy. There are no FDA-approved systemic therapies for the treatment of NF1-associated cNF.

About Plexiform Neurofibromas (PN)

NF1-associated plexiform neurofibromas (PNs) are tumors originating from the nerve sheath that grow through and around nerves and may involve multiple nerve branches. Thirty to fifty percent (30-50%) of patients with NF1 will harbor PNs, which can undergo malignant transformation. PN-related morbidities, including pain, disfigurement and functional impairment are primarily caused by the direct impact of the tumor on surrounding structures and can be life-threatening when they compress vital organs or when they become malignant.

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 cutaneous and 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 Study PAS-004-103 in cNF and PN, including response rates, durability, and safety observations, and their significance, the Company's planned Phase 2 study of PAS-004 in cNF and the FDA's clearance of the Company's IND to proceed with such study, the Company's clinical data from its Phase 1 dose-escalation study of PAS-004 in advanced solid tumors, 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, including 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 related to the initiation, design, timing, enrollment, and conduct of clinical trials and interactions with regulatory authorities, and 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

Company Contact:

Patrick Gaynes
Corporate Communications
pgaynes@pasithea.com 

For Investor Inquiries:

Mike Moyer
Managing Director, LifeSci Advisors, LLC
mmoyer@lifesciadvisors.com 

Photos accompanying this announcement are available at:
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FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did Pasithea's PAS-004 trial show for cutaneous neurofibromas?

All 15 evaluable participants had reductions in summed target cutaneous-neurofibroma surface area, with a median best reduction of 41%. Among eight evaluable participants receiving the 4, 8 and 12mg doses planned for Phase 2, the median best reduction was 46%.

What is the next trial planned for Pasithea's PAS-004 in cutaneous neurofibromas?

The FDA cleared the investigational new drug application for a randomized, double-blind, placebo-controlled Phase 2 trial in approximately 200 adults with NF1-associated cutaneous neurofibromas. Study PAS-004-201 will evaluate three once-daily doses; the planned dose range is 4mg to 12mg.

How were cutaneous neurofibromas measured in Pasithea's PAS-004 study?

Target lesions were measured in triplicate using digital calipers, recording length and width. Fifteen evaluable participants had 71 target lesions measured at baseline. Surface area was calculated from length and width, and longest diameter was also reported. Eight lesions at the planned Phase 2 doses were surgically removed for analysis and included using their last measurement before removal.