Pasithea Therapeutics Corp. reported that Cohort 7 of its first‑in‑human Phase 1 study of the macrocyclic MEK inhibitor PAS‑004 has been completed. The 37 mg capsule cohort enrolled 12 patients and recorded no treatment‑related adverse events during the dose‑limiting toxicity period, a key safety milestone that supports the drug’s tolerability profile.
The pharmacokinetic data from Cohort 7 remained dose‑proportional, with a peak‑to‑trough ratio below two and an area‑under‑the‑curve of 6,690 ng·h/mL. Pharmacodynamic analysis showed continuous suppression of the MAPK pathway over a 24‑hour cycle, confirming sustained target engagement at this dose level. Compared with earlier cohorts, the safety and PK/PD consistency strengthens the case for escalating to the next dose tier.
Pasithea’s progress is significant for both oncology and RASopathy indications. A favorable safety profile at 37 mg suggests that chronic dosing could be feasible, a critical requirement for treating MAPK‑driven solid tumors and genetic disorders such as neurofibromatosis type 1. In a market dominated by established MEK inhibitors, PAS‑004’s macrocyclic structure and demonstrated target engagement may offer a differentiating advantage if efficacy signals emerge in later trials.
CEO Dr. Tiago Reis Marques emphasized the importance of the safety data: “The absence of dose‑limiting toxicities in Cohort 7 gives us confidence to move forward with dose escalation and to pursue both oncology and RASopathy programs.” He added that the sustained MAPK suppression observed “supports our strategy of chronic dosing to achieve durable pathway inhibition.”
The company’s stock had fallen nearly 60 % in the week preceding the announcement, reflecting broader market concerns and valuation pressures. While the positive safety update may temper some of that pessimism, investors will likely focus on the next‑phase data and the eventual demonstration of clinical efficacy before reassessing the company’s valuation.
The Safety Review Committee has recommended escalation to Cohort 8 (45 mg capsules). Pasithea will continue to monitor safety, PK, and PD parameters as it advances to the next dose level, with the goal of establishing a therapeutic window that balances efficacy and tolerability for future oncology and RASopathy trials.
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