Investigators Look to Cut Breast Cancer Recurrence With Posttrastuzumab Therapy

Investigators at the Dan L. Duncan Comprehensive Cancer Center at Baylor College of Medicine hope to reproduce results of a successful phase 2B trial of GP2 peptide/G-CSF in patients with HER2-equivocal or -positive breast cancer who have received a standard course of trastuzumab, reference or biosimilar form, following surgery.

GP2 plus GM-CSF is believed to stimulate a tumor-specific cytotoxic immune system response against HER2-positive cancer cells. Phase 2 studies help determine whether a drug shows any activity against the target disease and assist with setting optimal dosing. Phase 3 trials assess the value of a drug in a clinical setting.

In the retrospective, placebo-controlled phase 2B trial, completed in 2018, after a median 5 years of follow-up, no cancer recurrences were observed in the adjuvant setting among patients with HER2-equivocal or -positive breast cancer who received the full course of 6 primary intradermal injections over the initial 6 months (P = .0338), according to subgroup analysis.

In that earlier study, the immune response, as measured by local skin tests and immunological assays, was potent, investigators said. In addition, among 138 patients who have received GP2 over 4 clinical trials, the treatment was well tolerated, with no serious adverse events attributable to the therapy, investigators said.

In the phase 3 trial, investigators hope to reproduce those results in preventing recurrence of HER2-equivocal or -positive breast cancer both post surgery and following an initial year of treatment with trastuzumab, including biosimilars.

GP2 is an investigational drug being developed by Greenwich LifeSciences of Stafford, Texas. Lead investigator and Greenwich LifeSciences CEO Snehal Patel pointed to the value of GP2 if it proves to be a reliable tool in reducing HER2-positive breast cancer recurrence. “We are addressing a potential market of up to $5 billion in a disease that affects 1 in 8 women, who if recur, will likely face metastatic breast cancer,” he said.

Reference

Patel SS, McWilliams DB, Fischette CT, et al. A prospective, randomized, multicenter, double-blinded, placebo-controlled phase III trial of the HER2/neupeptide GP2 + GM-CSF versus bacteriostatic saline/WFI placebo as adjuvant therapy after any trastuzumab-based therapy in HER2-positive women with operable breast cancer. Presented at: 2020 San Antonio Breast Cancer Symposium; December 8-11, 2020. Abstract OT-13-03. https://www.sabcs.org/Portals/SABCS2016/2020%20SABCS/Final%20PDF%20Docs%20111620_All%20PDF%20File%20No%20Embargoed%20Abstracts.pdf?ver=2020-11-17-095626-250