Insistent data after a single administration of their drugs is enough to warrant a late stage program, Sophiris Bio is adamant on pressing forward. Topsalysin is being developed as treatment for localized prostate cancer that is only activated in the presence of PSA associated with prostate cancer and benign prostatic hyperplasia.
The drug is designed to kill tumors without affecting healthy tissue, and is administered via injection directly into the prostate tumor, which in presence of PSA binds to cancer cells to form a pore across the cancer cell membranes causing them to rupture.
Six months after a single administration of the drug 10 out of 37 patients treated had clinical response, 6 of which experienced total destruction of the tumor during early phase 2b trials; however a readout now says additional benefit was not observed on targeted biopsy six months after re-treatment among those who showed no response to initial dose. Analyst Christopher Raymond suggests the 6 month data remains compelling.
Lead investigator Professor Mark Emberton M.D says they remain encouraged by safety and biopsy data from the first administration, adding they are in the process of designing a protocol for potential phase 3 registration study using a single administration of the drug. Randall Woods, CEO, says they are in the final stages of finalizing design for the trial and will be submitting it to regulators in the E.U first then in the USA for feedback.
According to the biotech follow up biopsy testing revealed that 41% of patients had partial responses that were clinically significant, and 32% had no response; and treatment with Topsalysin was reported to be well tolerated by all patients throughout the study. Topsalysin has previously met endpoints in 2015 during a phase 3 study with 479 BPH with patients having symptoms improve over 12 months.
