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

(NASDAQ:KTTA) Pasithea Therapeutics Corp. announced positive clinical data from its ongoing Phase 1/1b study (PAS-004-103, NCT06961565) of PAS-004, a next-generation macrocyclic oral MEK inhibitor, in adults with neurofibromatosis type 1 (NF1)-associated plexiform neurofibromas (PN) and cutaneous neurofibromas (cNF), presented at the 2026 European Neurofibromatosis Conference in Vienna, Austria. Dr. Tiago Reis Marques, Chief Executive Officer, stated that the substantial reductions in cNF size represent an encouraging clinical signal in a condition with no FDA-approved systemic treatments, and that these reductions have deepened with longer treatment, including at the lowest doses tested. Dr. Kartik Krishnan, Chief Medical Officer, highlighted the potential of PAS-004 to provide broad, visible improvements for patients through a systemic treatment approach and noted early activity in plexiform neurofibromas, with reductions in tumor volume across all dose levels and two participants meeting the REiNS threshold for partial response. Study PAS-004-103 is an ongoing multicenter, open-label Phase 1/1b trial at five sites in the United States, Australia, and South Korea, enrolling adults with NF1 and symptomatic, inoperable, incompletely resected, or recurrent PN, and evaluating up to 7 cNFs per participant. As of September 15, 2026, 19 participants have been enrolled across six cohorts (4, 8, 12, 15, 18, and 24mg), with 15 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. All 15 evaluable participants showed reductions in summed target cNF surface area at best response, with a median best reduction of 41%. Among eight evaluable participants at 4, 8, and 12mg, the median best reduction was 46%, and all six participants at 4mg and 8mg achieved reductions greater than 40%. 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, with the 4mg cohort reaching a median reduction of 71% at Cycle 15. At the 4, 8, and 12mg doses, 27 of 37 target cNFs (73%) were reduced by at least 25% in longest diameter, meeting the REiNS shrinkage criterion, and among the 29 cNFs not resected, 24 (83%) met the REiNS criterion, with a median best reduction in longest diameter of 39%. 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, with the 15mg participant achieving a 22.5% reduction at the first on-treatment MRI. 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), with two Grade 3 events (asymptomatic increases in blood creatine phosphokinase) resolving after a one-week dose interruption. At the 4 to 12mg doses, dermatitis acneiform (rash) and diarrhea occurred in 33% and 11% of participants, respectively. 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), supporting once-daily dosing. 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 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.