Blog by Arthur N. Brodsky, PhD, published on Cancerresearch.org on 27 March 2020. Click here to access the original article.

Just weeks after International Human Papilloma Virus (HPV) Awareness Day, new results from two long-time Cancer Research Institute (CRI) scientists highlighted the promise of immunotherapy against HPV-associated cervical cancer.

In a phase 1/2 study, women with advanced, recurrent, or metastatic cervical cancer were treated with the combination of an HPV-targeting vaccine and standard-of-care chemotherapy. Of 72 evaluable patients, 43 percent had their tumors shrink.

Led by Cornelis J. M. Melief, M.D, Ph.D., and Sjoerd H. van der Burg, Ph.D., this clinical breakthrough was the latest fruit borne by the duo, both of whom have been supported by CRI during their time at Leiden University Medical Center in the Netherlands. In addition to being a member of the CRI Scientific Advisory Council, Melief was the recipient of the 2019 AACR-CRI Lloyd J. Old Award in Cancer Immunology and is currently the chief scientific officer at ISA Pharmaceuticals. Van der Burg, who earned his doctorate in Melief’s lab in 1998, is also affiliated with ISA as a member of their Scientific Advisory Board, as well as the Oncode Institute.

In 2002, CRI-funded preclinical work by Melief and van der Burg provided an early proof of principle that therapeutic HPV vaccines could eliminate HPV-associated cancers. To do so, they used synthetic long peptide (SLP) vaccines to target the E6/E7 oncoproteins produced by the HPV16 strain.

Next, they demonstrated that HPV-targeting vaccines could clear pre-malignant lesions. However, vaccination wasn’t effective against advanced cancers because of the presence of immunosuppressive myeloid cells. By adding chemotherapy to the treatment regimen, the current study sought to decrease the number of myeloid cells and thereby enable more potent anti-tumor immune responses after vaccination, especially by the immune system’s “killer” T cells.

In many patients, the combination appears to have done just that.

Two weeks after chemotherapy, when patients’ myeloid cells were at their lowest point, varying doses of the ISA-101 vaccine were administered. Half of them also received a molecule called pegylated type 1 interferon that may help boost adaptive immune responses. Overall, about one-third of patients analyzed had low levels of HPV-targeting T cells after chemotherapy alone and prior to vaccination. Post-vaccination, HPV-specific T cell responses were detected at all dose levels, and “the patients with higher than median strength responses survived the best,” Melief told CRI.

“These results, provided they are validated in larger trials, could lead to significantly improved care for patients with cervical cancer.”

In another ongoing study, this vaccine paired well with checkpoint blockade immunotherapy in patients with advanced head and neck cancer—another cancer linked to HPV infection. A similar trial will soon be testing that approach in cervical cancer, according to Melief, who believes we might benefit from going even further with vaccine combinations.

“Last year, we demonstrated the synergy between vaccination and anti-PD-1 checkpoint immunotherapy in patients with recurrent or metastatic HPV+ head and neck cancer. It is therefore tempting to combine all three therapeutic measures—anti-PD-1, vaccination, and chemotherapy—for additional synergy because chemotherapy and anti-PD-1 act by non-overlapping mechanisms. This chemotherapy combination also pinches in nicely with other types of immunotherapy because many types of late-stage cancer induce this kind of myeloid cell-mediated immunosuppression in patients.”

For more on this promising vaccine approach and the long scientific journey that led to this point, read our 2019 interview with Dr. Melief.