Regulators in the United States and Europe have approved Amgen's talimogene laherparepvec, a genetically modified live oncolytic herpesvirus therapy that replicates inside cancer cells and causes them to rupture and die.

Both the FDA and the European Medicines Agency (EMA) approved the first-in-class therapy for treatment of melanoma lesions that cannot be removed completely by surgery. In a 436-patient pivotal trial, tumours shrank for at least 6 months in 16% of virus-treated participants and in only 2% of patients in the comparator arm (J. Clin. Oncol. 33, 2780–2788; 2015). Treated patients trended towards a 4.4-month longer median overall survival than control patients, but the FDA noted that treatment “has not been shown to improve overall survival”. The most common side effects were fatigue, chills, pyrexia, nausea, influenza-like illness and injection site pain.

Amgen is now testing the oncolytic virus in colorectal, head and neck, and breast cancer.

At least seven other oncolytic viruses are in development, with companies tapping into genetic engineering approaches and the innate tumour-killing properties of viruses to treat a range of cancers (Nat. Rev. Drug Discov. 14, 369–371; 2015). Companies are also optimistic that oncolytic viruses will benefit from being paired with checkpoint-blocking antibodies that prime the immune system to take down cancer cells. Amgen, for example, is testing its talimogene laherparepvec in combination with Bristol-Myers Squibb's anti-CTLA4 (cytotoxic T lymphocyte-associated antigen 4) antibody ipilimumab and with Merck & Co.'s anti-PD1 (programmed cell death protein 1) antibody pembrolizumab.

Analysts forecast annual global sales of nearly US$400 million for talimogene laherparepvec by 2020, shows the Thomson Reuters Cortellis database. Analysts at BCC Research have estimated that the global market for oncolytic viruses will reach $6.4 billion by 2023.