At Learn Look Locate, we recognize that treatment doesn’t end at the doctor’s office—pharmacists play a crucial role in guiding patients through the latest advancements in breast cancer care. That’s why we’re launching a brand-new series with our Medical Advisor, Alexander Cosimano, PharmD, CSP, Walgreens Specialty Pharmacist. In this series, Alex will break down new therapies and FDA approvals in a way that’s easy to understand—so you can feel informed, empowered, and ready to talk with your care team.
HER2-positive breast cancer makes up about 15–20% of all breast cancer cases. A promising vaccine, GLSI-100, is currently being studied with support from the FDA’s Fast Track designation—a status that helps accelerate the review process and bring treatments to patients more quickly.
GLSI-100 is a peptide vaccine designed to “train” the immune system to recognize and attack cancer cells. It combines:
Together, these components stimulate the body’s killer T-cells to detect and destroy HER2-positive cancer cells, to prevent recurrence.
Right now, GLSI-100 is being studied in patients who:
Not yet. GLSI-100 is currently available only through clinical trials. If you’re interested, speak with your oncologist about whether you may qualify for FLAMINGO-01 (NCT05232916), or visit ClinicalTrials.gov for more details.
GLSI-100 could represent a major step forward in helping HER2-positive breast cancer survivors lower their risk of recurrence. While it’s not available outside of trials yet, early results are encouraging and highlight the importance of ongoing research.
Q. What is GLSI-100?
A: GLSI-100 is a peptide vaccine (GP2 + GM-CSF) being studied to help the immune system’s T-cells recognize and attack HER2-positive breast cancer cells, with the goal of lowering recurrence risk.
Q. Is GLSI-100 fast-tracked by the FDA?
A: Yes. In September 2025, the FDA granted Fast Track designation to GLSI-100 for certain HER2-positive patients who carry the HLA-A*02 genetic marker and have completed trastuzumab-based therapy.
Q. What evidence do we have so far?
A: ● In a Phase II follow-up, patients treated with GLSI-100 showed an ~80% reduction in recurrences at five years in the HER2 3+ subgroup.
● No new serious safety concerns were reported in that study.
● A larger Phase III trial (FLAMINGO-01) is underway to confirm these results.
Q. Who might be eligible?
A: GLSI-100 is currently being studied in people who:
● Had Stage I–III HER2-positive breast cancer
● Completed trastuzumab-based therapy (Herceptin®)
● Are HLA-A*02 positive
Final eligibility is determined by the clinical trial.
Q. Can I get the vaccine now?
A: Not yet. GLSI-100 is only available through clinical trials such as FLAMINGO-01 (NCT05232916). If you’re interested, ask your oncologist about eligibility or visit ClinicalTrials.gov.
Q. How common is HER2-positive breast cancer?
A: HER2-positive breast cancer accounts for about 15–20% of all breast cancer cases, though the percentage can vary depending on the population studied.
At Learn Look Locate, we believe education doesn’t stop with your doctor. Specialty pharmacists play a critical role in cancer care—especially when it comes to navigating new therapies like GLSI-100.
Walgreens Specialty Pharmacists are specially trained in oncology, meaning they understand not just medications, but also the unique challenges that breast cancer patients face. From helping you manage side effects to answering questions between appointments, they are a trusted partner in your journey.
In situations like this—where new treatments are emerging—pharmacists can help patients feel informed, supported, and prepared to have meaningful conversations with their care teams.
We are deeply grateful to have Walgreens Specialty Pharmacists as part of Learn Look Locate, guiding our community with expertise and compassion.
This educational content was created in paid collaboration with Walgreens.
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