Streamlined Synthesis and Structure-Activity Relationship Analysis of 2-Amidothiophene-3-Carboxamides Targeting...

Area of Science:

• Medicinal Chemistry
• Virology
• Drug Discovery

Background:

• Influenza viruses pose a significant global health risk due to rapid evolution and resistance to existing therapies.
• The PA-PB1 interface of the influenza RNA polymerase complex is a promising target for novel antiviral small molecules.
• Previous work identified compound 1, a PA-PB1 inhibitor with a cycloheptathiophene-3-carboxamide scaffold.

Purpose of the Study:

• To design and synthesize novel cycloheptathiophene-3-carboxamide derivatives.
• To investigate the impact of structural modifications, particularly at the C-5 position, on antiviral activity and aqueous solubility.
• To develop an efficient synthetic route for 2-amidothiophene-3-carboxamide analogs.

Main Methods:

• Synthesis of a new series of derivatives (compounds 2-16) based on scaffold 1.
• Structure-activity relationship (SAR) studies to correlate chemical modifications with biological activity.
• Evaluation of antiviral potency using EC50 values and cytotoxicity using CC50 values.
• Assessment of aqueous solubility.
• Enzyme-linked immunosorbent assay (ELISA) and molecular docking studies to confirm the mechanism of action (PA-PB1 inhibition).

Main Results:

• Compound 9 (C-5 phenyl analog) exhibited potent anti-influenza activity with sub-micromolar EC50 values (0.19-1.11 µM) and low toxicity (CC50 > 100 µM).
• Compound 5 (C-5 methyl analog) demonstrated significantly improved aqueous solubility (75.2 µM) while retaining low-micromolar potency (EC50 = 2 µM) and low toxicity (CC50 > 100 µM).
• All tested compounds maintained the PA-PB1 interaction inhibition mechanism, confirmed by ELISA and docking studies.

Conclusions:

• Modifications at the C-5 position of the cycloheptathiophene-3-carboxamide scaffold are critical for balancing anti-influenza potency and aqueous solubility.
• Compound 9 represents a highly potent influenza inhibitor, while compound 5 offers an improved solubility profile.
• These findings provide valuable insights for the development of next-generation influenza therapeutics targeting the PA-PB1 interface.