Aprepitant, also known as Emend, is a potent and selective neurokinin-1 (NK-1) receptor antagonist utilized primarily in the management of nausea and vomiting associated with cancer chemotherapy. With a CAS number of 170729-80-3, it demonstrates high affinity for the NK-1 receptor, exhibiting an IC50 value of 0.1 nM and a Kd value of 86 pM.Chemically, it is classified under the molecular formula C23H21F7N4O3, possessing a molecular weight of approximately 534.43 g/mol. Its structural features include a morpholine ring substituted with specific aryl groups, contributing to its pharmacological properties.
It works by inhibiting the binding of substance P to NK-1 receptors within the central nervous system, thereby exerting its antiemetic effects. This mechanism is crucial in reducing the incidence of chemotherapy-induced nausea and vomiting (CINV), significantly enhancing the quality of life for patients undergoing cancer treatment.
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Chemical Formula |
C23H21F7N4O3 |
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Exact Mass |
534.15 |
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Molecular Weight |
534.43 |
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m/z |
534.15 (100.0%), 535.15 (24.9%), 536.16 (3.0%), 535.15 (1.5%) |
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Elemental Analysis |
C, 51.69; H, 3.96; F, 24.88; N, 10.48; O, 8.98 |
Prevention and Treatment of Chemotherapy-Induced Acute and Delayed Nausea and Vomiting
Aprepitant is a highly selective neurokinin 1 receptor antagonist and a key agent for the symptomatic management of nausea and vomiting in clinical practice. It is primarily indicated for the prevention and intervention of chemotherapy-induced nausea and vomiting (CINV) in oncology patients, covering both acute and delayed emesis, and compensates for the limitations of conventional antiemetics.
Chemotherapy-induced nausea and vomiting are among the most common adverse reactions in cancer treatment. Acute emesis generally occurs within 24 hours after chemotherapy administration, while delayed emesis develops 24 to 120 hours post-chemotherapy.
The latter presents greater challenges for clinical intervention due to its prolonged onset and duration.
Capable of crossing the human blood-brain barrier, Emend directly acts on the emesis regulatory pathways in the central nervous system and blocks the transmission and activation of emetogenic signals. It is applicable to patients receiving moderately and highly emetogenic chemotherapy regimens for most solid tumors and hematological malignancies. With specific efficacy against clinically prevalent delayed nausea and vomiting, Emend effectively relieves recurrent emesis in the late stage of chemotherapy.
Prevention of Postoperative Nausea and Vomiting Complications
Beyond oncology chemotherapy, Emend is extensively used in perioperative care for the prophylactic management of postoperative nausea and vomiting (PONV) following general anesthesia. As a common anesthesia-related complication after surgery, PONV frequently occurs after prolonged general anesthesia for abdominal, gynecological and major orthopedic procedures. It adversely affects patients' postoperative oral intake, rest and physical recovery, and may further lead to physical discomfort, emotional anxiety and other secondary issues in severe cases.
Emend is mainly administered for prophylaxis in high-risk populations for PONV, including female patients, non-smokers, individuals with a history of postoperative vomiting, and patients undergoing prolonged general anesthesia. Boasting a long duration of action, it provides sustained protection throughout the high-risk period of over 24 hours after surgery, markedly reducing the incidence of PONV and minimizing its interference with postoperative recovery. Currently, it is routinely applied for prophylactic symptomatic management during the perioperative period of various surgical procedures.
Expanded Clinical Applications in Special Scenarios
Emend is suitable for multi-day consecutive chemotherapy. For cancer patients undergoing multiple cycles of continuous chemotherapy, it delivers sustained antiemetic effects and meets the requirements for adverse reaction control during long-course antitumor therapy.
In addition, it is used to prevent nausea and vomiting in patients with special physical conditions, such as elderly and frail cancer patients, patients with a history of motion sickness, and those with poor treatment tolerance.
It helps prevent sudden emetic symptoms during chemotherapy and improves patients' physical comfort throughout treatment.
In the clinical symptomatic treatment system, Emend also serves as an adjuvant therapy for refractory nausea and vomiting. For patients with recurrent emesis unresponsive to other antiemetics, it acts as an important therapeutic option to optimize the whole-process prevention and control system for emesis, adapting to a full range of complex clinical treatment scenarios.
Solubility
Emend exhibits prominent lipophilic and hydrophobic properties. It is freely soluble in common organic solvents such as dichloromethane, methanol, ethanol and acetone, and soluble in ethyl acetate. It is practically insoluble in water, with extremely low solubility in acidic and neutral aqueous media. Its solubility only increases slightly in weakly alkaline systems. Such properties make it suitable for the preparation of solid dosage forms, and also serve as an important physicochemical basis for its oral absorption and lipid-phase distribution.
Chemical Stability
The drug shows excellent stability when stored in solid state at room temperature under dark and dry conditions, with no tendency to decompose. It tolerates weakly acidic and neutral environments well and maintains structural stability under normal conditions.
However, degradation occurs under extreme conditions. Prolonged heating in strongly acidic media causes cleavage of ether bonds and detachment of side chains. Strongly alkaline environments may lead to ring-opening of the triazolinone heterocycle and structural damage.
High temperature and intense light exposure can trigger oxidative degradation of fluorinated benzene rings and side chains, resulting in darkening of color and reduction of drug purity.
Key Characteristics and Compatibility
Emend possesses good optical stability and hardly undergoes racemization during conventional storage, so chiral purity is set as a key quality control index. In addition, it has relatively high chemical inertness. No incompatibility reactions occur with most pharmaceutical excipients at room temperature, presenting favorable physicochemical compatibility that meets the requirements for routine pharmaceutical production and storage.
The aprepitant molecule contains three chiral centers, which impose stringent requirements on stereochemical purity. The major challenges of its synthesis lie in precise control of chiral configurations and improvement of atom economy.
Currently, the mainstream manufacturing process is an optimized green synthetic route developed by Merck. Abandoning the original multi-step and low-efficiency procedures, this convergent synthesis route features simplified workflows and fewer by-products, making it suitable for large-scale industrial production.
In the initial stage, N-benzylethanolamine and glyoxylic acid are used as starting materials. A condensation reaction is performed to produce the key oxazinone intermediate, forming the core scaffold of the drug.
Subsequent asymmetric epoxidation and low-temperature stereoselective reduction reactions are carried out to construct the cis configuration of the morpholine ring, strictly controlling the 2R and 3S chiral structures and preventing the formation of inactive enantiomers. The low-temperature reduction system ensures high stereospecificity, which is critical to guaranteeing pharmaceutical purity.
Upon completion of the core scaffold, 3,5-bis(trifluoromethyl)phenethyloxy and 4-fluorophenyl functional groups are sequentially attached to assemble the side chains. Finally, a triazolone side chain is linked via a methylene bridge to yield crude Emend.
The crude product is then purified through crystallization-induced asymmetric transformation and repeated recrystallization to remove impurities and stereoisomers, yielding high-purity crystalline powder.
The optimized process reduces the total synthetic steps to 8–10, significantly increasing the overall yield. Meanwhile, it eliminates the use of heavy metal reagents, cutting environmental pollution, and has now become the standard process for industrial production.
The research and development of Emend originated from neuropharmacological studies in the late 1980s and early 1990s. At that time, the medical community confirmed that substance P, a neuropeptide, triggers the vomiting reflex by activating central neurokinin 1 (NK1) receptors. Conventional antiemetics only acted on the acute emetic pathway and showed no efficacy against delayed vomiting, presenting prominent therapeutic limitations. Based on these findings, Merck launched a dedicated research program for NK1 receptor antagonists, aiming to develop novel antiemetic agents capable of crossing the blood-brain barrier and long-term inhibiting emetogenic signals.
The period from 1990 to 1997 marked the key phase of lead compound optimization. Leveraging structure-activity relationship analysis, the research team modified a series of candidate molecules and finally identified Emend with a morpholine ring structure. This compound features high receptor selectivity, excellent central nervous system penetration and favorable metabolic stability, effectively resolving the low bioavailability issue of early drug candidates. Preclinical animal studies verified its potent efficacy against both acute and delayed vomiting induced by chemotherapeutic agents, demonstrating great potential for clinical application. Core structural patents were filed in 1995 and officially granted in 1998.
After 2000, multi-center Phase III clinical trials were successfully conducted to validate the pivotal role of Emend in chemotherapy-induced emesis management. In 2003, it was approved for marketing by the U.S. Food and Drug Administration (FDA) under the brand name Emend, becoming the world's first commercially available NK1 receptor antagonist. Its indications were later expanded to postoperative antiemesis and pediatric use. The drug has filled the clinical gap in the treatment of delayed vomiting and revolutionized the antiemetic regimen for cancer chemotherapy.
Assay for Content
Reversed-phase high performance liquid chromatography (RP-HPLC) is the mainstream method. Octadecylsilane-bonded silica gel is used as the chromatographic column, and a mixture of acetonitrile and water serves as the mobile phase for gradient elution. The detection wavelength is set at 210 nm or 220 nm, and the external standard method is adopted to calculate the content of the active pharmaceutical ingredient. Featuring good resolution and high accuracy, this method is the preferred test method specified in pharmacopoeias and internal enterprise quality standards.
Related Substances Test
HPLC is also applied to separate and determine synthetic intermediates, degradation impurities and stereoisomers. A longer chromatographic column is used to improve separation efficiency, and the limits of related substances are strictly controlled. A dedicated chiral chromatographic column is employed for the separation and detection of chiral isomers to monitor enantiomeric impurities and ensure optical purity.
System Suitability and Other Test Items
All tests shall comply with system suitability requirements, including acceptable theoretical plate number, tailing factor and repeatability. Water content and residual solvents are determined by Karl Fischer method and gas chromatography (GC) respectively. Heavy metals and ignition residues are tested in accordance with general principles of pharmacopoeias. In advanced testing scenarios, LC-MS is combined to identify and trace unknown impurities, supporting process optimization and quality control.
FAQ
What class of drug is aprepitant?
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Aprepitant is in a class of medications called antiemetics. It works by blocking the action of neurokinin, a natural substance in the brain that causes nausea and vomiting.
What are the common side effects of aprepitant?
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However, as with many medicines, it may cause certain side effects in some people, including tiredness and dizziness. Make sure you know how you react to APREPITANT before you drive a car or operate machinery. Small, frequent meals or eating a snack before your chemotherapy treatment may help you to tolerate it better.
What should I avoid while taking aprepitant?
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Avoid grapefruit and grapefruit juice. Birth control pills and other hormone-based birth control may not work as well to prevent pregnancy. Use some other kind of birth control also, like a condom, when taking this drug and for 1 month after the last dose. Tell your doctor if you are breast-feeding.
Is aprepitant safe for long-term use?
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Emerging evidence suggests that continuous use is not only safe, but also effective in patients with nausea and vomiting refractory to multiple lines of antiemetic therapy.
Does aprepitant make you sleepy?
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Common side effects include tiredness or weakness, diarrhea, or hiccups. Aprepitant is available in multiple forms, including a capsule or liquid you take by mouth. It is also available as an injectable form given into a blood vessel by a health care provider.
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