(UroToday.com) The 2025 American Society of Clinical Oncology Genitourinary (ASCO GU) cancers symposium held in San Francisco, CA between February 13th and 15th 2025, was host to the Poster Session B: Urothelial Carcinoma. Dr. Youyan Guan presented Abstract 763: Phase Ib/II clinical trial of oncolytic virus intravesical irrigation for preventing recurrence after TURBT in patients with recurrent high-risk NMIBC.
Oncolytic virus therapy is an emerging cancer treatment strategy that has shown promise in non-muscle-invasive bladder cancer (NMIBC). OH2 injection, a recombinant oncolytic virus derived from a genetically modified herpes simplex virus type 2 (HSV-2) strain (HG52), has demonstrated efficacy in certain malignancies.1
This study aimed to evaluate the safety and preliminary efficacy of intravesical OH2 injection as a preventive irrigation therapy for high-risk NMIBC patients who had failed first-line preventive treatment. Investigators enrolled patients with pathologically confirmed high-risk NMIBC who had undergone TURBT after failing prior intravesical therapy and had no residual tumor at the time of enrollment.
Inclusion criteria included:
- Adequate organ function
- ECOG performance status of 2 or less
- Ineligible for or refused radical cystectomy.
Those with muscle invasive or locally advanced metastatic bladder cancer were excluded. Following enrollment, patients received OH2 with normal saline intravesical instillation. The instillation was given every two weeks for 5 times, followed the sixth instillation after 3 weeks, then once a month until they completed a year.
The investigators evaluated the 6-month and 12-month recurrence-free survival (RFS) rates and safety of the OH2 instillation during the induction and maintenance treatment.
A total of 30 patients were planned to enroll in this clinical trial. However, at the time of data analysis, only 9 high risk NMIBC patients could be analyzed at this time. Most of the patients (66%) received BCG treatment before.
Patients treated with OH2 had a 6-month recurrence-free survival (RFS) rate of 66.7% and a 12-month RFS rate of 55.6%, with a median RFS of 353 days. Notably, one patient who had previously failed BCG treatment achieved the longest RFS in the study, approaching two years.
Regarding safety, adverse effects were consistent with the known safety profile of OH2. The most commonly reported issues were transient genitourinary symptoms, likely related to prior TURBT, but these did not worsen during treatment. No significant adverse effects directly attributed to OH2 instillation were observed.
Dr. Guan concluded his poster presentation with the following key points:
- OH2 injection is the first domestically developed oncolytic virus therapy in China to be used for intravesical treatment of recurrent high-risk NMIBC.
- Preliminary data (n=9) suggest that OH2 intravesical instillations are safe, though further research is needed to evaluate its long-term efficacy.
Presented by: Youyan Guan, MD, Department of Urology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. Beijing, China.
Written by: Julian Chavarriaga, MD – Urologic Oncologist at Cancer Treatment and Research Center (CTIC) via Society of Urologic Oncology (SUO) Fellow at The University of Toronto. @chavarriagaj on Twitter during the 2025 Genitourinary (GU) American Society of Clinical Oncology (ASCO) Annual Meeting, San Francisco, CA, Thurs, Feb 13 – Sat, Feb 15, 2025.
References:
- Wang Y, Jin J, Wu Z, Hu S, Hu H, Ning Z, Li Y, Dong Y, Zou J, Mao Z, Shi X, Zheng H, Dong S, Liu F, Fang Z, Wu J, Liu B. Stability and anti-tumor effect of oncolytic herpes simplex virus type 2. Oncotarget. 2018 May 15;9(37):24672-24683. doi: 10.18632/oncotarget.25122. PMID: 29872496; PMCID: PMC5973869.