PharmaEngine, Inc. (TWO: 4162) today announced the phase 1 results of a phase 1b/2 clinical study evaluating NBTXR3 (PEP503) activated by radiotherapy with concurrent chemotherapy in locally advanced or unresectable rectal cancer patients were presented at the 2021 American Society of Clinical Oncology Gastrointestinal Cancers Symposium (ASCO-GI 2021). The study is performed at 2 medical centers in Taiwan and enrolled 20 patients in the dose-escalation phase. Subjects received PEP503 intratumoral injection before radiotherapy with concurrent chemotherapy (CCRT), and received surgery after the CCRT. The safety data showed good tolerability of PEP503 even at the highest dose level (22% of tumor volume). There were no observed adverse events directly associated with PEP503, and the toxicity profile of CCRT was not affected.

More than 70% of patients in the study showed objective tumor response after CCRT. Around 90% of patients underwent total mesorectal excision (surgery) with R0 resection; and near 20% achieved pathological complete response (pCR). Half of the patients receiving surgery had good tumor regression. Based on the above data, PharmaEngine has proceeded to phase 2 part at 3 medical centers in Taiwan, starting from October, 2020, for further evaluation of the efficacy of PEP503 in rectal cancer patients.