CHAPEL HILL, NC (TheStreet) -- Cempra (CEMP - Get Report) shares are up 7% to $12.54 Tuesday on the announcement of clean results from a heart rhythm safety study of of its experimental antibiotic solithromycin.
A single supra-therapeutic (above therapeutic level) dose of solithromycin caused no adverse effect on heart rhythm in patients, according to results from what is known as a "thorough Qt" study released today by Cempra.
Why would a safety study be so meaningful for a drug that is already in phase III studies?
Recall, solithromycin is tied to the legacy of Sanofi's SNY Ketek, a similar antibiotic which never lived up to big sales expectations because of significant toxicity issues which cropped after approval. Solithromycin, like Ketek, is a next-generation macrolide, so investors are watching closely for the appearance of any potential safety problems.
Macrolides can cause heart rhythm abnormalities in patients -- severe enough in some cases to increase the risk of sudden death. This is why investors were anxiously awaiting the results from Cempra's thorough Qt study of solithromycin. Based on the data announced today, it appears the safety risk is gone, and in fact, solithromycin may have a comparative advantage over other macrolide antibiotics when it comes to heart safety.
Last July, I said Cempra's solithromycin has the potential to be a blockbuster antibiotic. Obviously, this will require positive results from ongoing phase III studies, results from which are expected later this year. Today's safety update is also important because it helps to remove an overhang.
Sobek is long Cempra.