GILBERT, Ariz. (July 10, 2025) – A new study at Banner MD Anderson Cancer Center offers new hope for patients with advanced melanoma who no longer respond to standard immunotherapies.
In a Phase II clinical trial, researchers found that a novel investigational treatment — RP1, a genetically engineered virus — used in combination with the immunotherapy drug nivolumab significantly shrank tumors in about one in three patients whose disease had progressed after standard treatment.
The trial enrolled 140 patients with advanced melanoma resistant to anti-PD-1 therapy, a common first-line immunotherapy. Historically, these patients have very few effective treatment options and face a median overall survival of just one year.
Notably, 15% of participants experienced a complete response, with all signs of cancer disappearing. Among those who responded, more than half remained in remission two years later.
“These are clinically meaningful results, especially when you consider the limited alternatives for patients once common therapy stops working,” said principal investigator Jiaxin Niu, MD, Ph.D. He is also the co-director of the lung cancer program at Banner MD Anderson.
The study also found that RP1 could shrink tumors that were not directly injected, including in organs like the liver and lungs—suggesting a systemic immune response. Patients responded regardless of tumor size, location, or specific genetic traits like BRAF mutations.
Importantly, the combination was well tolerated. While most patients experienced mild side effects such as fatigue or fever, only 12.9% had serious treatment-related side effects. No treatment-related deaths occurred.
RP1 is a modified herpes simplex virus that has been engineered to target and destroy cancer cells while stimulating a broader immune response. It delivers immune-activating proteins, which enhance tumor cell destruction and immune system engagement.
Biomarker analyses from the study revealed increases in immune activity in the tumor in patients who responded to treatment, helping researchers better understand the therapy’s mechanism of action and laying the groundwork for future research.
While the trial was not randomized and did not include a control group, the results compare favorably to historical outcomes.
“The durability of the response is particularly encouraging, and we are hopeful that these results will support FDA approval,” said Dr. Niu. “I am deeply grateful to our courageous patients and their families, as well as to my dedicated colleagues and supportive staff. Their strength and commitment made this option possible for other patients in the near future.”
“This is a significant new option for patients with melanoma. In the broader context, it also marks an important step toward establishing our center as a leading hub for oncology research in the Southwest,” said Matthew Callister, MD, senior physician executive for Banner MD Anderson.
This research and care took place at the T.W. Lewis Melanoma Center of Excellence at Banner MD Anderson.
For more information about the study, visit https://doi.org/10.1200/JCO-25-01346.
About Banner MD Anderson Cancer Center
Banner MD Anderson Cancer Center delivers cancer care to patients through the partnership of Banner Health and MD Anderson Cancer Center. Banner MD Anderson offers focused disease-specific expertise in the medical, radiation and surgical management of the cancer patient; an evidence-based, multidisciplinary approach to patient care; access to clinical trials and new investigative therapies; state-of-the-art technology for the diagnosis, staging and treatment of all types of cancer; oncology expertise in supportive care services. For more information, visit www.BannerMDAnderson.com.
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