You may have many alternatives other than fusion assay (pseudotyped virus entry assay, viral capture, HIV-1 gp120-CD4 interaction inhibition assay, siRNA screening). I recommend the "pseudotyped assay". Reporter genes (luciferase or GFP) inserted into the viral genome. The small molecules are tested for their ability to inhibit the entry of pseudotyped viruses into target cells. A reduction in reporter gene expression indicates inhibition of viral entry.

Thank you for the answer. How to perform HiV-1 gp120 - CD4 interaction inhibition assay? @Mert Karaca

Performing an HIV-1 gp120-CD4 interaction inhibition assay involves studying the interaction between the viral envelope protein gp120 and the host CD4 receptor and assessing the inhibitory effects of different molecules or compounds. Generally you need; HIV-1 gp120 protein, CD4 receptor protein, test compounds or molecules to assess inhibition, ELISA plates, blocking buffer (BSA or milk), wash buffer (PBS maybe), detection antibodies (e.g., anti-His or anti-CD4 antibodies), substrate for color development (TMB), microplate reader. Assay conditions may vary depending on your specific experimental setup and the assay kit or protocol you are using. I recommend reviewing the methods of previous studies. You can also investigate it using flow cytometry. There are complex protocols available that can provide simple observations in this regard or enable more detailed investigations. Good luck

Thank you @Mert Karaca