Published Today at AACR 2021, Showing Peak Immunity after 6 Months of GP2 Treatment, Resulting in 100% Disease Free Survival from Recurring Breast Cancer
Greenwich LifeSciences, Inc. (Nasdaq: GLSI) (the “Company”), a clinical-stage biopharmaceutical company focused on the development of GP2, an immunotherapy to prevent breast cancer recurrences in patients who have previously undergone surgery, today presented a poster of the final 5 year GP2 Phase IIb clinical trial immune response data at the 2021 AACR Annual Meeting. Immune response is the primary mechanism of action for GP2 and is critical to developing dosing and booster treatment strategies that are designed to achieve and sustain peak immunity, as well as to prevent metastatic breast cancer recurrences.
It has been previously reported that the completion of the GP2+GM-CSF Primary Immunization Series (PIS) reduced recurrence rates to 0% over a 5 year follow-up period in HER2 3+ patients who had received a standard course of trastuzumab after surgery. The abstract and poster present the final immune response results over the 5 year follow-up period, assessing peak immunity compared to baseline and between patients treated with GP2+GM-CSF versus GM-CSF alone, including by HER2 status.
Summary of the Final 5 Year Immune Response Data as Previously Presented:
- Potent immune response data supports the previously reported clinical outcome of 0% metastatic breast cancer recurrences over 5 years of follow up, if a patient completes the Primary Immunization Series over the first 6 months of GP2 treatment.
- Statistically significant peak immunity was reached after 6 months of GP2 treatment as measured in both the Dimer Binding Assay and the DTH skin test.
- HER2 3+ population immune response was similar to the HER2 1-2+ population immune response, suggesting the potential to treat the HER2 1-2+ population (including triple negative breast cancer) with GP2 immunotherapy in combination with trastuzumab (Herceptin) based products and other clinically active agents.
- Broad based immune response suggests that GP2 immunotherapy and Herceptin based products may also have the potential to treat other HER2 1-3+ expressing cancers.
Dr. Thompson commented, “The analysis of the immune response data in the Phase IIb trial provides mechanistic confirmation of treatment effect correlated with the clinical response previously reported. GP2 treated patients, independent of their HER2 status, experienced a potent immune response to GP2, far greater than patients treated with placebo. In addition, this data has provided us with insight that will guide the upcoming Phase III trial. We believe that monitoring immune response will be an important aspect of the Phase III trial.”
Greenwich LifeSciences, Stafford, TX
Background: The final analysis of the GP2 prospective, randomized, placebo-controlled, single-blinded, multicenter Phase IIb trial (NCT00524277) investigating GP2+GM-CSF versus GM-CSF alone in HLA-A02 patients administered in the adjuvant setting to node-positive and high-risk node-negative breast cancer patients with HER2 status (IHC 1-3+) is now complete with 5 year follow-up. It has been previously reported that completion of the GP2+GM-CSF Primary Immunization Series (PIS) reduced recurrence rates to 0% over a 5 year follow-up period in HER2 3+ patients, who received a standard course of trastuzumab after surgery. Here we present the final immune response results, assessing peak immunity compared to baseline and between GP2 treated patients versus placebo, including by HER2 status. Interim analyses for this trial have been previously reported by Mittendorf et al.
Methods: Each GP2-treated patient was scheduled to receive 6 GP2+GM-CSF intradermal injections over the first 6 months as part of the PIS and 4 GP2+GM-CSF booster intradermal injections every 6 months thereafter. Placebo patients received GM-CSF only intradermal injections. Immune responses to GP2 were measured over time using delayed-type-hypersensitivity (DTH) skin tests and CD8 Tcell dimer binding assays.
Results: This basket trial explored HER2 3+ patients, who received a standard course of trastuzumab after surgery, and HER2 1-2+ patients, who did not receive trastuzumab after surgery. A DTH reaction was used to assess in vivo immune responses in patients (n=145). The DTH orthogonal mean was measured 48-72 hours after injection using the sensitive ballpoint-pen method and are compared using a Wilcoxon Rank-Sum. For GP2 treated patients, there was a significant increase in DTH reactions after the PIS compared to baseline DTH reactions. The DTH orthogonal mean in GP2 treated patients at baseline had a median 0.0mm versus 10.8mm after the PIS. For patients receiving GM-CSF alone, the DTH orthogonal mean prior to and after the PIS had a median of 0.0mm. In addition, the DTH reactions after the PIS were significantly greater in GP2 treated patients than in placebo patients (10.8mm vs. 0.0mm, p=0.009) and the DTH immune response in GP2 treated patients was similar between HER2 3+ and HER2 1-2+ patients. Ex vivo immune responses were assessed by phenotypic clonal expansion assays in the majority of patients (n=114). GP2-specific CTLs were quantified using the Ig:A2 dimer assay and demonstrated a gradual expansion over time reaching statistical significance approximately 6 months after the PIS compared to baseline in the GP2 treated patients (n=53, p=0.010) but not in the control patients (n=39, p=0.165).
Conclusions: Immunological data comparing peak immunity to baseline and GP2 treated patients to placebo showed that GP2 treated patients, independent of HER2 status, experienced a significant increase in their immune response while those receiving GM-CSF only did not. Future studies may explore the use of immune responses to assess: immunogenicity of GP2 by HLA type, timing of boosters to sustain immunity, clinical site performance, and the discontinuation of treatment for non-responders.
About the AACR Annual Meeting 2021
The AACR is the first and largest cancer research organization dedicated to accelerating the conquest of cancer and has more than 48,000 members residing in 127 countries and territories. The AACR Annual Meeting program covers the latest discoveries across the spectrum of cancer research — from population science and prevention; to cancer biology, translational, and clinical studies; to survivorship and advocacy — and highlights the work of the best minds in research and medicine from institutions all over the world.
About Breast Cancer and HER2/neu Positivity
One in eight U.S. women will develop invasive breast cancer over her lifetime, with approximately 266,000 new breast cancer patients and 3.1 million breast cancer survivors in 2018. HER2/neu (human epidermal growth factor receptor 2) protein is a cell surface receptor protein that is expressed in a variety of common cancers, including in 75% of breast cancers at low (1+), intermediate (2+), and high (3+ or over-expressor) levels.
About Greenwich LifeSciences, Inc.
Greenwich LifeSciences is a clinical-stage biopharmaceutical company focused on the development of GP2, an immunotherapy to prevent breast cancer recurrences in patients who have previously undergone surgery. GP2 is a 9 amino acid transmembrane peptide of the HER2/neu protein. In a randomized, single-blinded, placebo-controlled, multi-center (16 sites led by MD Anderson Cancer Center) Phase IIb clinical trial, no recurrences were observed in the HER2/neu 3+ adjuvant setting after median 5 years of follow-up, if the patient received the 6 primary intradermal injections over the first 6 months (p = 0.0338). Of the 138 patients that have been treated with GP2 to date over 4 clinical trials, GP2 treatment was well tolerated and no serious adverse events were observed related to GP2 immunotherapy. Greenwich LifeSciences is planning to commence a Phase III clinical trial using a similar treatment regime as the Phase IIb clinical trial. For more information on Greenwich LifeSciences, please visit the Company’s website at www.greenwichlifesciences.com and follow the Company’s Twitter at https://twitter.com/GreenwichLS.
Barbara Jacoby is an award winning blogger that has contributed her writings to multiple online publications that have touched readers worldwide.