H3B-5942 free base

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MedKoo CAT#: 408068

CAS#: 2052128-15-9 (free base)

Description: H3B-5942 is a selective, irreversible and orally active estrogen receptor covalent antagonist. In vitro comparisons of H3B-5942 with standard-of-care (SoC) and experimental agents confirmed increased antagonist activity across a panel of ERαWT and ERαMUT cell lines. In vivo, H3B-5942 demonstrated significant single-agent antitumor activity in xenograft models representing ERαWT and ERαY537S breast cancer that was superior to fulvestrant.

Chemical Structure

H3B-5942 free base
CAS# 2052128-15-9 (free base)

Theoretical Analysis

MedKoo Cat#: 408068
Name: H3B-5942 free base
CAS#: 2052128-15-9 (free base)
Chemical Formula: C31H34N4O2
Exact Mass: 494.2682
Molecular Weight: 494.639
Elemental Analysis: C, 75.28; H, 6.93; N, 11.33; O, 6.47

Price and Availability

Size Price Availability Quantity
50.0mg USD 750.0 2 Weeks
100.0mg USD 1150.0 2 Weeks
200.0mg USD 1850.0 2 Weeks
500.0mg USD 2850.0 2 Weeks
1.0g USD 3850.0 2 Weeks
2.0g USD 6750.0 2 Weeks
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Related CAS #: 2052132-46-2 (HCl)   2052128-15-9 (free base)    

Synonym: H3B-5942; H3B 5942; H3B5942;

IUPAC/Chemical Name: (E)-4-((2-(4-((E)-1-(1H-indazol-5-yl)-2-phenylbut-1-en-1-yl)phenoxy)ethyl)amino)-N,N-dimethylbut-2-enamide


InChi Code: InChI=1S/C31H34N4O2/c1-4-28(23-9-6-5-7-10-23)31(25-14-17-29-26(21-25)22-33-34-29)24-12-15-27(16-13-24)37-20-19-32-18-8-11-30(36)35(2)3/h5-17,21-22,32H,4,18-20H2,1-3H3,(H,33,34)/b11-8+,31-28+


Appearance: Solid powder

Purity: >98% (or refer to the Certificate of Analysis)

Shipping Condition: Shipped under ambient temperature as non-hazardous chemical. This product is stable enough for a few weeks during ordinary shipping and time spent in Customs.

Storage Condition: Dry, dark and at 0 - 4 C for short term (days to weeks) or -20 C for long term (months to years).

Solubility: Soluble in DMSO

Shelf Life: >3 years if stored properly

Drug Formulation: This drug may be formulated in DMSO

Stock Solution Storage: 0 - 4 C for short term (days to weeks), or -20 C for long term (months).

HS Tariff Code: 2934.99.9001

Preparing Stock Solutions

The following data is based on the product molecular weight 494.639 Batch specific molecular weights may vary from batch to batch due to the degree of hydration, which will affect the solvent volumes required to prepare stock solutions.

Recalculate based on batch purity %
Concentration / Solvent Volume / Mass 1 mg 5 mg 10 mg
1 mM 1.15 mL 5.76 mL 11.51 mL
5 mM 0.23 mL 1.15 mL 2.3 mL
10 mM 0.12 mL 0.58 mL 1.15 mL
50 mM 0.02 mL 0.12 mL 0.23 mL

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1. Puyang X, Furman C, Zheng GZ, et al. Discovery of Selective Estrogen Receptor Covalent Antagonists for the Treatment of ERαWT and ERαMUT Breast Cancer. Cancer Discov. 2018;8(9):1176–1193. doi:10.1158/2159-8290.CD-17-1229

2. Furman C, Hao MH, Prajapati S, et al. Estrogen Receptor Covalent Antagonists: The Best Is Yet to Come. Cancer Res. 2019;79(8):1740–1745. doi:10.1158/0008-5472.CAN-18-3634

Additional Information

Mutations in estrogen receptor alpha (ERα) that confer resistance to existing classes of endocrine therapies are detected in up to 30% of patients who have relapsed during endocrine treatments. Because a significant proportion of therapy-resistant breast cancer metastases continue to be dependent on ERα signaling, there remains a critical need to develop the next generation of ERα antagonists that can overcome aberrant ERα activity.