Pimavanserin is a synthetic pharmaceutical active ingredient belonging to the class of selective serotonin 5-HT2A receptor inverse agonists. It is primarily associated with the treatment of hallucinations and delusions associated with Parkinson’s disease psychosis. Pimavanserin has the CAS Number 706779-91-1, molecular formula C25H34FN3O2, and molecular weight 427.55 g/mol. The compound is also known by the development code ACP-103.
Pimavanserin is a synthetic urea derivative containing a fluorophenyl group, a substituted benzyl group and a 1-methylpiperidinyl moiety. It is chemically distinct from Pimavanserin Tartrate, which is the salt form used in the marketed pharmaceutical product. The free base has CAS Number 706779-91-1, while Pimavanserin Tartrate has CAS Number 706782-28-7.
The FDA's original quality assessment identifies Pimavanserin Tartrate as the drug substance and reports a molecular weight of 1005.20 g/mol for the tartrate salt, corresponding to two Pimavanserin molecules and one L-tartaric acid molecule. The corresponding free-base molecular weight is 427.55 g/mol. The FDA also describes the drug substance as a white to off-white powder and reports that Pimavanserin Tartrate melts with decomposition at 167–177°C.
Pimavanserin is a serotonergic pharmaceutical ingredient that acts primarily as a selective 5-HT2A receptor inverse agonist. Unlike conventional antipsychotic agents that primarily target dopamine receptors, Pimavanserin was developed to provide antipsychotic activity through serotonergic receptor modulation. PubChem identifies its pharmacological role as a 5-hydroxytryptamine 2A receptor inverse agonist and antipsychotic agent.
The FDA-approved pharmaceutical product contains Pimavanserin Tartrate. FDA documentation indicates that 20 mg Pimavanserin Tartrate corresponds to 17 mg Pimavanserin, while 40 mg Pimavanserin Tartrate corresponds to 34 mg Pimavanserin. This distinction is important when calculating API quantities and documenting pharmaceutical formulations.
Pimavanserin API quality control involves identity, assay, related substances, moisture and other applicable pharmaceutical quality attributes. FDA documentation confirms that Pimavanserin drug substance was subject to extensive pharmaceutical quality evaluation during development. The FDA review also discusses impurity and degradant control for the drug substance, emphasizing the importance of an established impurity profile for pharmaceutical manufacturing.
Analytical methods used for Pimavanserin can involve reversed-phase liquid chromatography and UV detection. Published stability work has used a C18 column, 150 × 4.6 mm, 5 µm, with UV detection at 210 nm for determination of Pimavanserin and related impurities. The reported method included a 0.05% level for the limit-of-quantitation standard used in impurity assessment. These analytical-method parameters should not, however, be confused with universal API release limits.
Pimavanserin can undergo chemical degradation and form related substances during pharmaceutical processing or storage. Published analytical studies have evaluated multiple impurities and degradation products under acidic, alkaline, neutral, oxidative, thermal and ultraviolet stress conditions. This demonstrates the importance of validated impurity testing and appropriate storage conditions for Pimavanserin pharmaceutical material.
FDA quality documentation confirms that impurity qualification and monitoring formed part of the regulatory assessment of Pimavanserin Tartrate drug substance. Because the official FDA review contains redacted sponsor-specific acceptance limits for some impurities, those limits should not be reconstructed or presented as universal numerical specifications.
Commercial chemical references report Pimavanserin Base as a solid with a reported melting point around 100–103°C, while research-grade suppliers commonly describe it as a white to off-white or pale solid. These physical-property values are useful for identification and characterization but should not automatically be treated as pharmacopoeial release specifications.
Pimavanserin is practically insoluble in water according to several chemical and research references, while it shows substantially better solubility in organic solvents such as ethanol or DMSO. Formulation properties can differ significantly between the free base and the tartrate salt, so the exact API form should always be specified in technical and regulatory documentation.
Pimavanserin Base should be stored and handled according to validated stability data and the applicable pharmaceutical specification. Research-grade material is commonly recommended for storage at −20°C, but research-storage recommendations should not automatically be represented as a commercial pharmaceutical API storage specification.
Pimavanserin API is therefore a specialized pharmaceutical ingredient with established serotonergic pharmacology and regulatory importance. Accurate differentiation between Pimavanserin Base and Pimavanserin Tartrate, together with validated assay and impurity testing, is essential for pharmaceutical manufacturing, formulation development and quality documentation.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Heavy Metals | NMT 10 ppm |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |