Heptamidine is an effective Pentamidine-related inhibitor of the calcium-binding protein S100B (Kd: 6.9 μM). It selectively kills melanoma cells with S100B over those without S100B. It is a useful tool for the investigation of Myotonic dystrophy.

S100B:(kd)6.9 μM

Heptamidine is a Pentamidine-S100B complex with two pentamidine molecules binding per monomer of S100B, acting as an inhibitor for S100B[1]. It rescues mis-splicing of minigene reporters in a HeLa cell DM1 model with an EC50 value of 15 μM. Compared to Propamidine and Pentamidine, Heptamidine (20 μM) does not significantly reduce CUG levels. It exhibits cytotoxicity at concentrations above 17.5 μM in HeLa cells expressing 960 CUG repeats[2].

Heptamidine (intraperitoneal injection; 20 or 30 mg/kg; 7 days) induces a dose-dependent reduction of exon 7a inclusion in HSALR mice, returning to wild-type levels (6±1%) at a 20 mg/kg dose. Myotonia is reduced from grade 3 to grade 1 (occasional myotonic discharge) or grade 0 at both 20 and 30 mg/kg [2].