On Tuesday, NLS Pharmaceutics AG (NASDAQ: NLSP) shares increased 10.58% after-hours to $2.30. Following a 12.43% spike during the regular session, this after-hours rise closed at $2.08. The company’s most recent preclinical data release at the 2025 Annual Meeting of the American Society of Clinical Psychopharmacology (ASCP), which is taking place this week from Tuesday to Friday at the Fairmont Scottsdale Princess in Arizona, was the main driver of the strong momentum.
Mazindol ER Shows Potential Against Fentanyl Dependence
NLS Pharmaceutics unveiled a study titled “Evaluating the Effects of Mazindol on Fentanyl Reward and Dependence in C57BL/6J Mice and Sprague-Dawley Rats (Study KO-943)” during a poster session scheduled for Thursday. Conducted in collaboration with Key-Obs SAS and several European academic partners, the study focused on the efficacy of Mazindol ER in preclinical models of opioid addiction.
The capacity of Mazindol to considerably lower fentanyl-induced conditioned place preference (CPP) in C57BL/6J mice at a dosage of 0.5 mg/kg was one of the main results. When tested by the Gellert-Holtzman scale, the same medication at 0.5 and 1.0 mg/kg significantly decreased opioid withdrawal symptoms in Sprague-Dawley rats, including agitation, salivation, and motor disruption.
A Novel Multi-Target Mechanism
The data suggest Mazindol’s effectiveness may stem from its unique multi-receptor activity. By partially agonizing the mu-opioid receptor, acting strongly on the 5-HT1A receptor, and modulating orexin-2 receptors, Mazindol offers a distinct pharmacological approach to combating opioid dependence. These properties make it a promising non-opioid alternative in addressing both reward and withdrawal dimensions of fentanyl addiction.
Implications Beyond Addiction
The treatment of illnesses of the central nervous system (CNS), especially ADHD, is affected by the study’s wider implications. Mazindol exhibits a dual impact in lowering opioid reward and withdrawal symptoms, in contrast to conventional stimulant and non-stimulant therapy.
This further differentiates Mazindol’s therapeutic profile and is consistent with earlier CNS studies, including data presented by Wigal et al. (2018). Clinical validation through forthcoming trials, including the planned NLS-6002 study, will be pivotal in advancing its development.

