[Ed. Note: Dr. KSS is an MD, PhD who writes about medicine and biotech stocks for the Irregulars. He has agreed to our trading restrictions, he choses his own topics, and his words and opinions are his own. Visit his Stock Gumshoe author page to see his past columns and most recent comments.]
Readers have written in asking for insight regarding yesterday’s news from Sophiris ($SPHS), a company we covered optimistically in 2014 because of its novel, relatively non-invasive approach to benign prostatic hyperplasia.
A common attack scheme in nature, used by antibiotics like defensin mimetics (of which $CTIX‘s brilacidin is an example), used by the parallel vertebrate immune system called complement (about which columns are coming), and by certain bacteria, is the elaboration of substances that burst holes in a target cell. Vital substances then leak out of the cell, membrane gradients break down, and life is no longer possible.
In the case of Sophiris, it exploited a system based on the Gram-negative pathogen Aeromonas, which releases proteins with the ability to self-assemble and bore a hole in a target cell membrane. Sophiris calls this reagent topsalysin. It didn’t exactly shine in BPH clinical trials, however, mainly because men in a placebo arm, whose glands were injected with mere saline, got most of the relief of their nocturnal urinary symptoms. This proved clearly that saline injections can shrink the prostate, which isn’t surprising (saline can be locally toxic), but that topsalysin added little to the effect.
The news of that trial caused shares to lose most of their value, and it was surprising, in fact. The science was solid: prostate specific antigen (PSA) is an enzyme that activates topsalysin, and so it should have “gone to town” within the gland. Topsalysin had good supporting pre-clinical data. But facts are pesky things, and a trial failure is a trial failure. The company could have proceeded by advancing mere salt-water injections into the prostate for BPH relief, but whether this idea could be patented isn’t clear, and it possesses no muscular intellectual property that could command high prices.
Sophiris has spent months attempting self-redemption, by having a go at topsalysin as a means of treating prostate cancer lesions that are contiguous, confined to the gland, based on a combination of MRI pictures and trans-rectal prostate images. At present most such lesions are treated by targeted irradiation, which kills and ...