Examining a Neoadjuvant Intravesical Oncolytic Measles Virus in Patients With Urothelial Carcinoma

Data from an ongoing phase I study were presented at the 2022 American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium, which described the safety and efficacy of an investigational oncolytic measles virus encoding thyroidal sodium iodide symporter (MV-NIS) treatment in patients with non-muscle-invasive bladder cancer (NIMBC), or muscle-invasive bladder cancer (MIBC). The researchers, led by Shruthi Naik, PhD, reported a surprising rate of tumor downsizing and pT0 pathology, as well as “significant immune infiltrate in post-treatment bladder tissue.”

Taken together, the study’s collaborators presented their findings as “compelling evidence that intravesical MV-NIS has clinical activity against UC,” and further recommended the “use of two doses of ∼1×10⁹ TCID₅₀ as the [recommended phase II dose (RP2D)] in future clinical studies for [Bacillus Calmette-Guerin (BCG)] unresponsive NMIBC or MIBC patients.”

At the time of the presentation, eight patients had been enrolled—four in the single-dose safety cohort, and four in the multi-dose expansion cohort. The intervention in the safety cohort was one-time intravesical ∼1×10⁹ TCID₅₀ MV-NIS at least one week prior to radical cystectomy (RC), and in the expansion cohort was two administrations at four and two weeks prior to RC. Tumor samples from the pre-treatment transurethral resection of bladder tumor (TURBT) and post-treatment RC were used to assess the safety and efficacy of MV-NIS.

Dr. Naik stated that intravesical MV-NIS was well-tolerated by all of the enrolled patients, with only a single adverse event (AE) attributed to MV-NIS treatment (grade I hematuria). Other AEs were related to post-surgery complications. Tumor downstaging was seen in four of the eight patients, and two patients in the expansion cohort achieved pT0 (no residual disease). Assessment of post-RC tumor specimens revealed the aforementioned significant immune cell infiltration in all specimens.

While the report noted that “detailed analyses are ongoing to characterize MV infection and immune infiltrate in bladder tissue,” the authors presented a very favorable opinion of the safety and efficacy of MV-NIS treatment for patients with NMIBC and MIBC. In closing, Dr. Naik also supplied the theory that “MV-NIS induced inflammation may act synergistically with checkpoint blockade therapies.”