Checkpoint inhibitors have already transformed the treatment of melanoma for some patients, but new data from Amgen suggest adding an oncolytic virus could add even more punch to the treatment.

Data from the phase 2 trial of Amgen’s cancer-busting virus Imlygic (talimogene laherparepvec) with Bristol-Myers Squibb’s CTLA4 inhibitor Yervoy (ipilimumab) in advanced melanoma—first reported at the American Society of Clinical Oncology (ASCO) this year—have now been published in peer review and show that combining the therapies doubles response rates compared to Yervoy alone.

Amgen’s head of R&D says that the trial provides an important proof-of-concept for combining the complementary mechanisms of an oncolytic viral immunotherapy and a checkpoint inhibitor to enhance antitumor effects, adding that the company wants to test Imlygic with other checkpoint inhibitors in “a variety of tumor types”.

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The trial results—published in the Journal of Clinical Oncology—show that the objective response rate for the combination came in at 39%, compared to 18% for Yervoy on its own. That pattern was also shared when it came to complete responses, at 13% for the duo and 7% for BMS drug given on its own.

Responses occurred in patients with and without visceral disease and in uninjected lesions after combination treatment, according to the paper.

It’s an important finding for Amgen, which needs to tap into the potential of Imlygic as part of combination cancer immunotherapies if it is to unlock the potential of the drug and expand its use beyond the nice of late-stage melanoma, for which it was approved in 2015. So far sales are small, and Amgen lumps the drug into its ‘other products’ category in earnings results with other drugs that collectively earned around $60 million in the second quarter.

It’s not the first time that Imlygic has shown its worth when given alongside a checkpoint inhibitor either. In 2014, the preliminary data from the phase 1b/2 MASTERKEY-256 trial of the drug paired with Merck & Co’s PD-1 inhibitor Keytruda (pembrolizumab) showed an ORR for the combination of around 56%. According to Amgen’s pipeline, the duo is in a phase 3 trial (KEYNOTE-034) due to generate preliminary results next year.

“Advanced melanoma is highly aggressive and can require multiple treatment approaches over the course of the disease,” commented Jason Chesney, M.D., lead author of the latest study and director of the James Graham Brown Cancer Center in Louisville, Kentucky.

“These data show that this combination of a checkpoint inhibitor plus Imlygic demonstrated a synergistic clinical effect and enhanced anti-tumor immune response in patients with metastatic melanoma.”