Vasomotor symptoms (VMS), more colloquially known as hot flashes or night sweats, are some of the most common symptoms in menopause. With a median duration of 7.4 years, vasomotor symptoms are also the most common reasons why women seek treatments for menopausal issues. Although mostly considered a nuisance, vasomotor symptoms can significantly affect quality of life, as women with 7 or more moderate to severe VMS daily have reported a decline in sleep quality, concentration, sexual activity, energy, and concentration. Although the pathophysiology of VMS is not fully understood, unpredictable fluctuation in estrogen levels is thought to be the main cause of VMS, as estrogen therapy has been one of the most effective treatments for VMS by relieving symptoms in as many as 95% of menopausal women. Women undergoing abrupt menopause due to oophorectomy also experienced more severe symptoms than those going through a gradual transition. Additionally, thermoregulatory dysfunction has been proposed as one of the three possible mechanisms for VMS in menopause. Estrogen is a potent neuromodulator, particularly in the hypothalamus, and has been shown to be involved as a negative regulator in generating Gonadotropin-releasing hormone (GnRH) pulse through the kisspeptin, neurokinin B, and dynorphin (KNDy) neurons. NK3, one of the receptors expressed in KNDy neurons, is activated by neurokinin B and can thus induce the release of GnRH. Lower estrogen levels during menopause will decrease the estrogen-mediated feedback loop and increase neurokinin B signalling, increasing the activity of KNDy neurons and therefore the activity of the temperature control center. By antagonizing NK3 receptors, neuronal signalling can be dampened to reduce VMS. Although hormone therapy is available for menopausal women, safety and tolerability concerns, such as an increased risk of stroke and venous thromboembolism or hormone-dependent cancer like breast cancer, can prevent some women from receiving this treatment. Fezolinetant, an NK3 receptor antagonist, was developed in response to this issue as well as more understanding of the role of NK3R in the hypothalamic-pituitary-gonadal (HPG) axis. Although previous NK3 receptor antagonists exist, such as osanetant and talnetant, only fezolinetant showed tangible effects on the HPC axis, potentially due to its favorable pharmacokinetics profile to cross the blood-brain barrier. Fezolinetant was approved by the FDA in May 2023 under the brand name Veozah. It was subsequently approved by the EMA in December 2023 for the same indication.
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Fezolinetant
Drug Overview
What is Fezolinetant?
To derive PDE/ADE, OEL, and OEB values, Masuu Global follows a scientifically justified, risk-based toxicological assessment approach in accordance with internationally recognized guidelines and industry best practices that are widely accepted by regulatory authorities, including European Medicines Agency (EMA), Pharmaceutical Inspection Co-operation Scheme (PIC/S), and Agência Nacional de Vigilância Sanitária (ANVISA).
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Regulatory Framework
Assessment Methodology
Masuu Global follows a scientifically justified, risk-based toxicological approach aligned with internationally recognized guidelines accepted by EMA, PIC/S, and ANVISA.
EMA – Guideline on Setting Health-Based Exposure Limits (HBELs)
Provides the framework for establishing scientifically justified PDE/ADE values for use in shared manufacturing facilities.
PIC/S – Shared Facilities and Contamination Control Guidance
Supports the application of HBEL-based approaches for cross-contamination prevention and cleaning validation.
ICH Q9 – Quality Risk Management
Provides a structured methodology for risk identification, assessment, control, communication, and review.
ICH M7 – Assessment and Control of DNA-Reactive (Mutagenic) Impurities (where applicable)
Applied for compounds with potential mutagenic or genotoxic concerns.
Risk-Based Toxicological Assessment
Comprehensive evaluation of available toxicological and pharmacological data, including NOAEL, LOAEL, BMDL, pharmacological potency, carcinogenicity, reproductive and developmental toxicity, sensitization potential, and target organ toxicity.
Weight-of-Evidence (WoE) Approach
Integration and critical review of all relevant data sources, including non-clinical studies, clinical studies, human exposure data, pharmacological information, post-marketing safety data, and structure–activity relationship (SAR/QSAR) assessments.
How We Work
Report Preparation Process
Every assessment moves through a rigorous five-stage workflow — from data gathering to regulatory-ready delivery.
Comprehensive Data Review
Assessment of pharmacology, toxicology, clinical data, literature, and available regulatory information.
Scientific Evaluation
Identification of critical endpoints and selection of appropriate exposure limits.
PDE / HBEL Derivation
Transparent and scientifically justified calculations aligned with global toxicological principles.
Ex-Agency Expert Review (Our Differentiator)
Reports are reviewed with an ex-agency perspective, bringing regulatory expectations, inspection readiness, and practical implementation into every assessment.
Final Report Delivery
Regulatory-ready reports with scientific rationale, calculations, and clear recommendations by certified toxicologists (ERT, UKRT and DABT).
Ex-Agency Advantage
Why Masuu Global?
Our ex-agency toxicologists bring a practical regulatory perspective that transforms how assessments are built, reviewed, and defended.
Regulatory expectation–driven assessments aligned with how authorities actually evaluate submissions.
Inspection-ready reports — scientifically defensible and audit-prepared from day one.
Faster review cycles with direct decision support from certified toxicologists (ERT, UKRT, DABT).
Practical implementation recommendations that translate science into actionable contamination control.
Reduced internal effort — offload complex assessments without sacrificing quality or defensibility.
Global reach across PDE/ADE, HBEL, OEL, OEB, cleaning validation, and impurity assessments.
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