Abstract CT123: Phase I/II trial of endoscopic intratumoral administration of OBP-301, a novel telomerase-specific oncolytic virus, with radiation in elderly esophageal cancer patients
Authors: Tanabe Shunsuke , Tazawa Hiroshi , Kagawa Shunsuke , Noma Kazuhiro , Takehara Kiyoto , Koujima Takeshi , Kashima Hajime , Kato Takuya , Kuroda Shinji , Kikuchi Satoru , Shirakawa Yasuhiro , Fujiwara Toshiyoshi 
Published: August 2015

Background: Telomerase activation is considered to be a critical step in carcinogenesis and its activity is closely correlated with human telomerase reverse transcriptase (hTERT) expression. We constructed an adenovirus 5 vector OBP-301 (Telomelysin), in which the hTERT promoter drives expression of E1A and E1B genes. OBP-301 causes selective replication and lysis of a variety of human cancer cells, and also inhibits the repair of radiation-induced DNA double-strand breaks, leading to radiosensitization. A phase I study has confirmed the safety and biological activity of intratumoral administration of OBP-301 alone in patients with advanced solid tumors in the United States. To further determine the feasibility, efficacy, and pharmacokinetics of OBP-301 in combination with radiotherapy, a phase I/II study was designed in elderly patients with esophageal cancer.

Methods: Patients with histologically confirmed esophageal cancer who were not eligible for standard treatments such as surgery and chemotherapy were enrolled into this study (UMIN000010158). Study treatment consisted of intratumoral needle injections of OBP-301 on days 1, 18, and 32 of treatment. Radiation therapy was administered concurrently over 6 weeks, beginning on day 4, to a total of 60 Gy. Virus administration was performed by intratumoral injection of the primary or metastatic tumor through a flexible endoscope. OBP-301 doses will be escalated initially in cohorts of two for the first 9 patients (1 × 10e10 and 1 × 10e11 virus particles [vp]). Six subsequent patients will receive the highest dose (1 × 10e12 vp). Virus shedding will be monitored in the saliva, sputum, urine, and plasma by a quantitative DNA-PCR assay.

Results: Six patients were enrolled and treated in the cohort with 1 × 10e10 vp of OBP-301. The patients comprised 4 males and 2 females, with median age of 83.5 years (range, 68 to 92 years). Only two patients had prior platinum-based chemotherapy. By November 2014, 3 patients completed treatment. All patients developed a transient, self-limited lymphopenia. A 92-year-old female showed a grade 4 lymphopenia classified as being possibly related to the treatment, although it recovered by the interruption of radiation. No other virus-related toxicities were noted. Objective responses were complete response (CR) in 2 patients and partial response (PR) with tumor regression, resulting in reopening of the esophagus, in 1 patient. Pathological analysis in biopsy specimens obtained from completely responded patients demonstrated no viable malignant cells for 3 to 5 months after the treatment completion.

Conclusions: Multiple courses of endoscopic OBP-301 injection in combination with locoregional radiotherapy were feasible and well tolerated in elderly patients with esophageal cancer, and appeared to provide clinical benefit.

Citation Format: Shunsuke Tanabe, Hiroshi Tazawa, Shunsuke Kagawa, Kazuhiro Noma, Kiyoto Takehara, Takeshi Koujima, Hajime Kashima, Takuya Kato, Shinji Kuroda, Satoru Kikuchi, Yasuhiro Shirakawa, Toshiyoshi Fujiwara. Phase I/II trial of endoscopic intratumoral administration of OBP-301, a novel telomerase-specific oncolytic virus, with radiation in elderly esophageal cancer patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT123. doi:10.1158/1538-7445.AM2015-CT123