An investigational vaccine called TPIV200 was found to be safe and generated strong T-cell immunity against tumor cells, significantly delaying recurrence in breast and ovarian cancer patients who had achieved complete responses in a Phase 1 trial.

The study, “Folate Receptor Alpha Peptide Vaccine generates immunity in Breast and Ovarian Cancer Patients,” appeared in the journal Clinical Cancer Research.

While significant advances have been made in the treatment of breast and ovarian cancer, a significant number of patients still experience distant relapse.

One way of extending cancer responses to treatment and improving survival is to increase anti-tumor immunity following standard treatment. This could be achieved through vaccination, creating tumor-specific T-cells that are actively scanning the body for new tumor cells.

The folate receptor alpha (FRa) protein is highly elevated in tumors of the breast and ovaries, but has little production in healthy tissues, and so is a promising target for cancer vaccines.

Researchers at the Mayo Clinic and TapImmune conducted a Phase 1 clinical trial (NCT01606241) to evaluate the safety and tolerability of TPIV200 — TapImmune’s anti-FRa vaccine — in 14 patients with ovarian cancer and eight breast cancer patients.

TPIV200 was administered as an adjuvant therapy to patients who had completed treatment with surgery, chemotherapy, radiation, or a combination of the above and had no signs of disease.

Participants were initially treated with one cycle of cyclophosphamide, followed by the vaccine. The vaccine was injected every 28 days, for up to six administrations.

In general, TPIV200 was found to be safe and well tolerated, with only one patient experiencing one severe treatment-related adverse effect due to a reaction at the injection site. All other reported side effects were mild in severity and manageable.

Also, 91% of patients developed specific immune responses against the folate receptor alpha protein, which were sustained for at least 12 months after immunization.

While the trial was not designed to assess the anti-cancer effectiveness of the vaccine, all participants remained alive for at least two years after starting the treatment.

In addition, the 10 ovarian cancer patients who entered the study in their first remission remained alive and disease-free for 528 days (roughly 1.5 years). This is significantly better than the progression-free survival rate of 313 days seen in historical controls treated with standard care.

TPIV200 was granted orphan drug designation by the U.S. Food and Drug Administration for the treatment of ovarian cancer.

It is also being evaluated in two additional Phase 2 trials for ovarian cancer patients. One (NCT02764333) is testing the vaccine in combination with Imfinzi in patients with platinum-resistant ovarian cancer. The second (NCT02978222), currently enrolling patients, will evaluate TPIV200 as a consolidation treatment following platinum-based chemotherapy in ovarian cancer patients.

“We believe that TPIV200 has a viable pathway toward potential approval [for treating ovarian cancer patients in first remission],” Peter Hoang, president and CEO of TapImmune, said in a press release. “Enrollment in the [new Phase 2] study is currently ongoing, and we expect to conduct an interim analysis by mid-2019, once the data from the first half of enrollment is achieved.”