Enzon Pharmaceuticals is shelving further development of its PEG-SN38 (EZN-2208) PEGylated irinotecan metabolite oncology candidate for metastatic colorectal cancer (mCRC) therapy at the end of its current Phase II study. The move has been made in light of what the firm calls evolving standards of care for mCRC, and the decision to concentrate clinical trials resources to “areas of study with nearer-term commercial potential,” notes Richard Mulligan, Ph.D., vice chair of Enzon’s board of directors.
Discontinuation of the mCRC program doesn’t preclude future evaluation of PEG-SN38 in the treatment of earlier stages of colorectal cancer, Dr. Mulligan notes. Ongoing PEG-SN38 studies in other indications will also not be affected. These include a Phase II study in metastatic breast cancer, a Phase I trial in pediatric cancer, and a Phase I combination study assessing PEG-SN38 plus Avastin® in solid tumors.
SN38 is an active metabolite of the cancer drug irinotecan. PEG-SN38 has been developed using Enzon’s PEGylation technology to offer therapeutic advantages over unmodified SN38 and its currently marketed prodrug, Camptosar. The firm claims its PEGylated version PEG-SN38 allows for parental delivery, increased solubility, higher exposure, and longer apparent half-life of the cancer to SN38.