Predicting If an Immune Checkpoint Drug Will Work

Drugs that activate the immune system to attack cancer in a process known as immune checkpoint blockade (ICB) are a focus of intense investigation. A number of them are already approved by the U.S. Food and Drug Administration (FDA) for various cancers; namely, the anti-CTLA4 antibody ipilimumab (Yervoy), two anti-PD-1 antibodies: pembrolizumab (Keytruda) and nivolumab (Opdivo), and three anti-PD-L1 drugs: atezolizumab (Tecentriq), avelumab (Bavencio) and durvalumab (Imfinzi). These ICB drugs have the potential to induce durable cancer regressions, but the majority of cancer patients just do not respond to them at all.

Biomarkers, signature molecules in the blood or other tissue, can sometimes be used to predict a patient’s response to a given treatment. But no reliable biomarkers exist for ICB, and this is a serious concern. Patients who may really benefit from ICB could be overlooked, and patients who are not likely to respond may receive useless (and very expensive) ICB treatment.

Most potential response predictors that have already been identified are not yet useful for one or all of the following reasons: they are not extensively validated, their significance is still uncertain and may differ from one cancer (or even one patient) to another, or they are technically challenging for routine use. These markers are addressed below. Continue reading…