Last reviewed: October 2026 · Cleared Peptides research team
Research use only. KX-826 (Pyrilutamide): Research Guide is supplied for laboratory research. It is not a drug, food, cosmetic, or dietary supplement. It is not FDA-approved. It is not for human or veterinary administration. This page does not give a dose or a method of administration. A study cited on this page describes that study’s own test article. It does not make this lot an approved medicine. To check a fact, open the PubMed or DOI link, confirm the authors and year, and match the paper’s compound name, CAS number, or sequence to the specification table. The full method is on the research desk page. Identity and purity for a lot are only what that lot’s certificate of analysis reports. An HPLC percentage is not a sterility result and not an endotoxin result unless the certificate prints those tests.
KX-826 is pyrilutamide, CAS 1272719-00-2. Formula C21H15F5N4O2S. It is a nonsteroidal androgen receptor antagonist, structurally distinct from RU58841 and from the steroidal ligand CB-03-01.
| Name | Pyrilutamide |
|---|---|
| Other names | KX-826; KX826 |
| CAS number | 1272719-00-2 |
| PubChem CID | 50940514 |
| Molecular formula | C21H15F5N4O2S |
| Molecular weight | 482.43 g/mol |
| Class | Nonsteroidal androgen receptor antagonist |
| Catalog status | Not a current Cleared Peptides lot. |
Receptor class
The published class is androgen receptor antagonism in receptor-binding work. This guide stops at that class. It does not describe a concentration, a vehicle, or a tissue outcome.
Analytical testing notes for Pyrilutamide
Pyrilutamide is identified in this guide as CAS 1272719-00-2, formula C21H15F5N4O2S, listed mass 482.43 g/mol. An identity test compares a measurement with those values. A mass spectrum is the usual measurement for a peptide. FTIR, when a certificate uses it, is a supporting infrared fingerprint and is less specific for closely related sequences.
Pyrilutamide is not a peptide. Identity and purity may be chromatographic (HPLC or GC) or spectroscopic, depending on the method named on the certificate. The peptide-specific notes below — sequence mass, 214 nm peptide-bond detection, and net peptide content — should not be assumed. Sterility and endotoxin still apply only when those lines are on the report.
Read the method named on the certificate before treating a purity percentage as an HPLC area-percent result. Small molecules in this library may be assessed by HPLC, gas chromatography, or spectroscopy. The instrument named on the report is the one that applies. A purity result still does not measure sterility, endotoxin, or a labeled fill weight.
A sterility test and an endotoxin test are not included in a chemical purity result. The compendial sterility test is a culture method (USP <71>): membrane filtration or direct inoculation into fluid thioglycollate medium and soybean-casein digest medium, incubated for 14 days. A PCR sterility screen uses a thermal cycler to detect microbial DNA and is a different method. The endotoxin test (USP <85> LAL, or USP <86> recombinant Factor C) reports endotoxin units with an incubating reader or a cartridge reader. Use a result only when that method is printed on the lot certificate. One published example in this catalog states that the report does not cover microbial contamination or endotoxins. The full description of equipment, standards, and how US laboratory accreditation works is in peptide analytical testing. Lot records are on the COA page.
Frequently Asked Questions
Is KX-826 the same as pyrilutamide?
Yes. KX-826 is the development code. The CAS number is 1272719-00-2.
Is it the same as RU58841?
No. Different structures and different CAS numbers.
Is this for human use?
No. Laboratory reference only.
Selected References
Registry records and peer-reviewed literature listed as scientific background. Citation does not imply endorsement, a benefit, or any use.
- PubChem CID 50940514, CAS 1272719-00-2. PubChem 50940514
Research Use Only Notice
This guide is provided for educational and laboratory reference purposes. It summarizes published structural and biochemical literature. It does not describe, recommend, or imply any use in humans or animals. These materials are not drugs, foods, cosmetics, or dietary supplements on this page, are not offered here as a treatment, and no dosing or administration instructions are provided. Cleared Peptides does not currently list a lot for every compound on this page.
