Viralytics lifted by FDA panel verdict on T-Vec

The positive verdict of the US FDA's Oncologic Drugs Advisory Committee (ODAC) on Amgen's T-Vec (talimogene laherparepvec) is proving a boost to other companies developing oncolytic immunotherapies, including Australia's Viralytics.

Earlier this week the ODAC voted 22 to 1 in favour of approval of T-Vec as a treatment for adults with melanoma, which dials down the regulatory risk a little for Viralytics and several other companies developing viral-based cancer treatments, such as Oncolytics Biotech and Genelux.

Oncolytic immunotherapies are delivered using viral vectors and cause the destruction of cancer cells, providing a direct anti-tumour effect and also spilling antigens that can help the immune system recognise and respond to the disease. To help this, T-Vec codes for the immune-stimulating cytokine GM-CSF.

The mechanism of action is thought to hold promise not only as a monotherapy but perhaps more significantly in combination with checkpoint inhibitors such as Merck & Co's Keytruda (pembrolizumab) and Bristol-Myers Squibb's Opdivo (nivolumab) and Yervoy (ipilimumab).

The Australian company reported data from the phase I/II STORM trial of its lead oncolytic immunotherapy Cavatak at the American Association of Cancer Research (AACR) meeting a few days ago which showed that it achieved tumour responses in melanoma in a dose-dependent manner that seem roughly equivalent to those seen in early T-Vec trials.

Meanwhile, an extension of the trial – called CALM – provided clear evidence that Cavatak was stimulating an immune response with the infiltration of cytotoxic T cells into melanoma tumours.

Cavatek could have one advantage over Amgen's candidate in that it can be delivered by intravenous injection, while T-Vec is administered by injection into melanoma lesions. That distinction means that Viralytics drug could, in theory at least, be used in a broader range of tumour types.

Analysts at Edison are optimistic about Cavatrak's prospects, suggesting it could be on the market in 2021 for melanoma, reaching a peak five years later with sales of $646 million. Additional launches in non-small cell lung, prostate and bladder cancer could increase that to well over $1 billion, they suggest.

'The initial indications from STORM and from the CALM extension trial support our thesis that Cavatak is likely to be highly efficacious when used in combination with the new checkpoint inhibitors,' they write in a research note.

Viralytics is already recruiting patients into a phase Ib study of Cavatak given as an intratumoural injection in combination with Yervoy, while the design of STORM means it could be combined with a checkpoint inhibitor in the final stage of the trial.

Among the other companies developing viral immunotherapies, Oncolytics has advanced its Reolysin therapy into phase II trials in breast, lung, colorectal and prostate cancer, while Genelux has taken its lead candidate GL-ONC 1 into a phase I/II trial in peritoneal cancer.

The T-Vec verdict 'lowers the regulatory risk for the entire field and raises the prospect that oncolytic virotherapy may soon become a commercial reality,' states Edison.