Fig 1: Purified PDE enzyme assays to test inhibition by HDCF104 or uHTS159.a Dose-response curve of HDCF104 as a blocker of PDE4B (IC50 of HDCF104 = 7.5 ± 0.32 μM). b Shows approximately two orders of magnitude lower IC50 of uHTS159 compared to HDCF104. c More modest inhibition of PDE3A was observed (in the μM range). (IC50 of uHTS159 = 0.06 ± 0.0021 μM as an inhibitor of PDE4B and 14.9 ± 1.57 μM for PDE3A). HDCF104 did not demonstrate inhibition of PDE3A at concentrations up to 100 μM (data not shown). IC50 of compounds calculated using GraphPad Prism 10 software, which was also employed for plotting all panels. Panels were arranged and presented with Affinity Designer software.