Cancer vaccines and oncolytic viruses

Two kinds of vaccine matter in oncology. Preventive vaccines stop the infections that cause cancer: HPV vaccination prevents most cervical cancers and hepatitis B vaccination prevents many liver cancers. Therapeutic vaccines are given to people who already have cancer and aim to train T cells against tumour proteins. They come in several forms: off-the-shelf vaccines against antigens shared by many tumours, personalised vaccines built from the mutations in one patient's tumour (usually as mRNA), dendritic cell vaccines made from the patient's own immune cells, and bacterial vectors engineered to carry tumour antigens.

Oncolytic viruses are a related idea from the other direction. A weakened or engineered virus infects tumour cells preferentially, multiplies inside them and bursts them, releasing tumour antigens and inflammatory signals that draw immune cells in. Talimogene laherparepvec, a modified herpes virus injected into melanoma deposits, was the first to be approved.

For decades therapeutic vaccines disappointed in late-stage trials, largely because tumours suppress the T cells they raise. The current wave pairs vaccines with checkpoint inhibitors so those T cells can act, and personalised mRNA vaccines are now in phase 3 trials in melanoma and other cancers. Sipuleucel-T, a dendritic cell product for prostate cancer, remains the one approved therapeutic vaccine in the older sense.