Development of a tumour selective precision immunovirotherapy expressing immune checkpoint inhibitors targeting LAG-3

Oncolytic viruses (OV) have significant potential to induce immunogenic cell death (ICD), turning immunologically “cold” tumours “hot”. This potential can be enhanced when combined with immune checkpoint inhibitors (ICI), such as LAG-3, which has been highlighted as a promising target for cancer therapy, as it acts as handbrake on immune cell activation following T-cell engagement and is also involved in T-cell homeostasis. However, some tumours appear refractory to this therapy, whilst systemic administration is associated with significant systemic toxicities. Combining OV and ICI into single agents capable of targeting tumour cells following intravenous delivery and mediating high level, tumour selective overexpression of ICI locally within the tumour microenvironment may enhance “on-target” and minimise “off-target” activity of immunotherapies.

Through extensive re-engineering of the viral capsid, our lab developed a tumour selective oncolytic adenovirus termed Ad5NULL-A20 which infects cells expressing the tumour selective integrin, αvβ6. We engineered Ad5NULL-A20 to overexpress a scFv-Fc of an anti-LAG-3 antibody. We demonstrate that in vitro, this Ad5NULL-A20.LAG-3 readily infects αvβ6 integrin positive tumour cells, expressing and secreted the scFv-Fc. The secreted scFv-Fc is completely functional and was shown to be as effective as the LAG-3 antibody as it binds and blocks LAG-3 mediated signalling in vitro at the similar concentration.

In conclusion, our study demonstrates the potential for a precision virotherapy to selectively transduce αvβ6 integrin positive tumour cells, expression and secreting a virally encoded immune checkpoint into. This has the potential to significantly “heat up” the tumour microenvironment and therefore has significant translational potential.