The vaccine, PGV-001, was given to 13 patients with solid tumors or multiple myeloma who had a high risk of recurrence after surgery or autologous stem cell transplant.
At last follow-up, four patients were still alive without evidence of disease and had not received subsequent therapy, four were alive and receiving therapy, three had died, and two were lost to follow-up.
Thomas Marron, MD, PhD , of Mount Sinai in New York presented these results in a poster at the American Association for Cancer Research Annual Meeting 2021: Week 1 ( Abstract LB048 ). Data in the abstract differ from the data presented.
“While cancer immunotherapy has revolutionized the treatment of cancer, we know that the majority of patients fail to achieve significant clinical response,” Dr. Marron said during his presentation. “One reason for this may be due to lack of preexisting primed T-cell response needed for PD-1 blockade to have a significant effect. To address this, personalized neoantigen vaccines may help prime an improved immune response against tumor cells.”
With this in mind, Dr. Marron and colleagues developed PGV-001, a vaccine consisting of patient-specific synthetic neoantigen peptides given to patients in the adjuvant setting.
Creating a personalized vaccine
The researchers synthesized PGV-001 for 15 patients with advanced malignancies. The patients first underwent tumor and germline DNA sequencing as well as HLA typing. Bulk RNA sequencing was performed on patients’ tumors as well.
Then, the researchers used a computational pipeline called OpenVax to identify candidate neoantigens. This pipeline, developed at Mount Sinai, identified and prioritized candidate neoantigens using predicted MHC class I binding affinity and neoantigen abundance.
OpenVax identified an average of 71.5 neoantigens per patient (range, 7-193). The goal was to synthesize a maximum of 10 peptides per patient, but two patients did not have an adequate number of neoantigens.
The peptides were administered over the course of 27 weeks along with poly-ICLC and a tetanus helper peptide. Before receiving their vaccine doses, patients with solid tumors had undergone curative-intent surgery, and those with multiple myeloma had undergone autologous stem cell transplant.
“Most experimental personalized cancer vaccines are administered in the metastatic setting, but prior research indicates that immunotherapies tend to be more effective in patients who have less cancer spread,” principal investigator Nina Bhardwaj, MD, PhD , of Mount Sinai, explained in a press release .
“We have, therefore, developed a neoantigen vaccine that is administered after standard-of-care adjuvant therapy, such as surgery in solid tumors and bone marrow transplant in multiple myeloma, when patients have minimal, typically microscopic, residual disease.”
Feasibility, safety, and immunogenicity
PGV-001 was synthesized for 15 patients and administered to 13 of them. Six of the 13 patients had head and neck squamous cell carcinoma, three had multiple myeloma, two had non–small cell lung cancer, one had breast cancer, and one had urothelial carcinoma.
Eleven patients received all 10 intended doses, and two patients received at least 8 doses.
“The vaccine was well tolerated, with only half of patients experiencing mild, grade 1 adverse events,” Dr. Marron said.
Transient injection site reactions occurred in four patients, and grade 1 fever was reported in one patient.
Immune monitoring is ongoing, but an initial analysis in one patient showed “robust responses” in CD4 and CD8 T cells by intracellular cytokine staining for interferon-gamma, tumor necrosis factor–alpha, and interleukin-2 after in vitro expansion in the presence of vaccine antigens, according to the researchers.
Dr. Marron noted that robust T-cell reactivity was seen at the completion of all 10 doses but was not seen after the 6th dose, and this supports the need for a prolonged dosing schedule.
Survival and subsequent therapy
At a mean follow-up of 880 days, four patients had no evidence of disease and had not received subsequent therapy. This includes one patient with stage IIIA non–small cell lung cancer, one with stage IVA HER-2 positive breast cancer, one with stage II urothelial carcinoma, and one with multiple myeloma.
Four patients were alive and receiving subsequent lines of therapy. Two of these patients had significant responses to anti–PD-1 therapy.
Three patients have died, two of whom had documented recurrence of their malignancy. The last two patients were lost to follow-up without documented recurrence.
“Our results demonstrate that the OpenVax pipeline is a viable approach to generate a safe, personalized cancer vaccine, which could potentially be used to treat a range of tumor types,” Dr. Bhardwaj said.
Trials combining neoantigens identified with the OpenVax platform are ongoing in patients with urothelial carcinoma and glioblastoma multiforme, Dr. Marron said.
The current study ( NCT02721043 ) is sponsored by Dr. Bhardwaj. Dr. Marron and Dr. Bhardwaj reported having no disclosures. Their colleagues disclosed relationships with Bristol Myers Squibb, Sema4, and Related Sciences.