Sirolimus, also known as rapamycin, is a macrocyclic lactone antibiotic produced by bacteria Streptomyces hygroscopicus, which was isolated from the soil of the Vai Atari region of Rapa Nui (Easter Island). It was first isolated and identified as an antifungal agent with potent anticandida activity; however, after its potent antitumor and immunosuppressive activities were later discovered, it was extensively investigated as an immunosuppressive and antitumour agent. Its primary mechanism of action is the inhibition of the mammalian target of rapamycin (mTOR), which is a serine/threonine-specific protein kinase that regulates cell growth, proliferation, and survival. mTOR is an important therapeutic target for various diseases, as it was shown to regulate longevity and maintain normal glucose homeostasis. Targeting mTOR received more attention especially in cancer, as mTOR signalling pathways are constitutively activated in many types of human cancer. Sirolimus was first approved by the FDA in 1999 for the prophylaxis of organ rejection in patients aged 13 years and older receiving renal transplants. In November 2000, the drug was recognized by the European Agency as an alternative to calcineurin antagonists for maintenance therapy with corticosteroids. In May 2015, the FDA approved sirolimus for the treatment of patients with lymphangioleiomyomatosis. In November 2021, albumin-bound sirolimus for intravenous injection was approved by the FDA for the treatment of adults with locally advanced unresectable or metastatic malignant perivascular epithelioid cell tumour (PEComa). Sirolimus was also investigated in other cancers such as skin cancer, Kaposi’s Sarcoma, cutaneous T-cell lymphomas, and tuberous sclerosis. The topical formulation of sirolimus, marketed as HYFTOR, was approved by the FDA in April 2022: this marks the first topical treatment approved in the US for facial angiofibroma associated with tuberous sclerosis complex.
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Sirolimus
Drug Overview
What is Sirolimus?
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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