Prostate Cancer Therapeutic Vaccine Presents Positive Results

A UK based immunotherapy company announced promising results from a phase 2a clinical trial of a therapeutic vaccine that could offer a new way to treat advanced prostate cancer. 

Vaccitech Limited and the University of Oxford announced on March 23, 2020, initial efficacy and safety data for ADVANCE, a clinical study testing VTP-800, an immunotherapeutic product in patients with metastatic castration-resistant prostate cancer (mCRPC). 

The study demonstrated that VTP-800 is safe and showed an encouraging efficacy trend in men with mCRPC.

VTP-800 is comprised of Vaccitech’s Chimpanzee Adenovirus Oxford 1 vector (PRIME) encoding the oncofetal antigen 5T4 (ChAdOx.5T4), followed by a Modified Vaccinia Ankara vector (BOOST) encoding the same antigen (MVA.5T4) administered in a heterologous prime-boost regimen.

In the 23 mCRPC patients who received VTP-800 in conjunction with an anti-PD-1, 5 patients (22%) had a >50% reduction in PSA level at any time point compared to baseline (median of 88 ng/ml). 

This compares favorably to the 9% response rate reported from a previous anti-PD-1 monotherapy study, KEYNOTE-199, which evaluated 243 mCRPC patients with similar baseline PSA levels. 

Additionally, four of the five ADVANCE patients (17.4%) maintained their response when tested three weeks later versus 5.8% in the KEYNOTE-199 study. 

One ADVANCE patient had a response with a PSA level of 0 at 24 weeks.

Whilst full analysis is still pending, initial safety data is comparable to that seen from dosing anti-PD-1 alone and there are no serious adverse events attributable to VTP-800.

ADVANCE patients received two cycles of VTP-800 four weeks apart and 480 mg of an anti-PD-1 agent on weeks 4, 8 and 12 of treatment. KEYNOTE-199 patients received 200 mg of anti-PD-1 every three weeks for up to 35 weeks.

“We are encouraged by these data and we believe they validate the application of our platform in other oncology indications using different antigens,” stated Bill Enright, Vaccitech CEO, in a press release.

“We look forward to continuing to work with Oxford University to explore options for future clinical studies to evaluate the added patient benefit VTP-800 can provide when combined with checkpoint inhibitors.”

Cancer vaccine development news published by Vax-Before-Cancer.