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?
Masuu Global provides end-to-end Environmental Risk Assessment (ERA) support for pharmaceutical and healthcare products, covering Phase I environmental exposure assessment, Phase II environmental fate and effects assessment, data-gap analysis, testing strategy, laboratory coordination and final regulatory-ready reporting.
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Regulatory Framework
Assessment Methodology
Masuu Global follows a science-based, tiered and risk-based ERA methodology, aligned with applicable international regulatory requirements. For human medicinal products, our approach is primarily guided by the EMA Guideline EMEA/CHMP/SWP/4447/00 Rev. 1, effective 1 September 2024, together with relevant OECD Test Guidelines and regional regulatory requirements.
EMA — Environmental Risk Assessment
Assessment of potential environmental exposure associated with the use, manufacture and disposal of medicinal products, with a structured approach to determine whether further environmental assessment is required.
Phase I — Environmental Exposure Assessment
Initial screening to determine potential environmental exposure, covering PEC calculation, physicochemical properties, usage and dosage data, environmental entry pathways, and persistence and fate considerations.
Phase II — Environmental Fate & Effects Assessment
Where Phase I indicates further assessment is required, Phase II provides detailed evaluation of environmental fate, persistence and ecological effects — including biodegradation, bioaccumulation, aquatic toxicity, PNEC derivation and PEC/PNEC risk characterisation.
OECD & International Testing Principles
Where laboratory studies are required, testing strategies are designed with consideration of relevant OECD Test Guidelines, GLP expectations and applicable regulatory requirements.
Risk-Based Environmental Assessment
Integration of physicochemical data, environmental fate information, ecotoxicological data, existing literature, published studies, regulatory databases, usage data, and environmental monitoring data.
Weight-of-Evidence (WoE) Approach
A scientifically justified WoE approach integrates existing data and avoids unnecessary testing wherever scientifically and regulatorily justified.
ERA Assessment Pathway
Phase I → Phase II → Risk Characterization
Each phase builds on the prior tier — screening first, escalating only when the evidence demands it.
Environmental Exposure Assessment
Initial screening to determine whether the substance requires progression to Phase II.
- Product and substance information review
- Indication, dose and usage assessment
- PEC calculation and environmental exposure estimation
- Physicochemical property review
- Initial environmental risk screening
- Determination of Phase II requirement
Environmental Fate & Effects
Detailed evaluation when Phase I triggers further assessment.
- Biodegradation, hydrolysis & photolysis
- Adsorption/desorption behaviour
- Bioaccumulation potential
- Algal, Daphnia and fish toxicity
- Chronic ecotoxicity, where required
- PEC/PNEC risk characterisation
Laboratory Coordination & Study Execution
When regulatory testing is mandatory, Masuu coordinates with qualified GLP/appropriate testing laboratories and specialized scientific partners — giving clients a single point of contact across the full testing lifecycle.
Final ERA Report — Contents
- Executive summary
- Substance & product information
- Environmental exposure assessment
- Phase I evaluation
- Phase II assessment (where applicable)
- Environmental fate assessment
- Ecotoxicological assessment
- PEC/PNEC calculations
- Risk characterisation
- Data gap evaluation
- Testing rationale
- Risk mitigation considerations
- References and supporting scientific evidence
How We Work
Report Preparation Process
Every ERA follows a structured, tiered workflow designed to deliver scientifically defensible and regulator-ready assessments.
Comprehensive Data Collection
Product, substance, usage, physicochemical, toxicological, environmental and regulatory information collected and reviewed.
Phase I Environmental Screening
Environmental exposure assessment and determination of whether the assessment can conclude at Phase I or requires progression.
Phase II Evaluation
Detailed environmental fate and ecotoxicological assessment when Phase II is triggered.
Data Gap & Testing Strategy
Missing information identified and available alternatives evaluated before recommending additional testing.
Consortium Testing Support
Where testing is mandatory, Masuu coordinates with qualified testing partners through its Consortium Model.
Scientific & Regulatory Review
Integration and critical review of generated and existing data by experienced scientific and regulatory experts.
Final ERA Delivery
Comprehensive ERA report with transparent methodology, scientific rationale, calculations, conclusions and regulatory recommendations.
Ex-Agency Advantage
Why Masuu Global?
Our experienced regulatory and scientific experts bring a practical regulatory perspective — helping clients understand not only what data are required, but why they are required and how regulators may evaluate them.
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