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GLSI-100

Phase 3

Breast Cancer | Monoclonal antibody | Oncology |Greenwich LifeSciences, Inc.|Last Updated: Aug 6, 2026

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials1
Total Enrollment2,250

FDA Designations

FAST_TRACK

Clinical trial landscape

GLSI-100 · 1 trial · 1 indication

Phase 3 1
NCT05232916Phase 3 Study to Evaluate the Efficacy and Safety of HER2/Neu Peptide GLSI-100 (GP2 + GM-CSF) in HER2/Neu Positive SubjectsBreast Cancer
RECRUITING2,250 Analytics
PHASE3RECRUITING
Phase 3 Study to Evaluate the Efficacy and Safety of HER2/Neu Peptide GLSI-100 (GP2 + GM-CSF) in HER2/Neu Positive Subjects
Breast CancerUnlock trial analytics

Study Endpoints

Primary Endpoints

Invasive Breast Cancer-free Survival (IBCFS)
Median 4 years of follow-up (interim analyses planned)

IBCFS is defined as the time from randomization (or the first dose of study medication if in the non-randomized arm) until the date of ipsilateral invasive breast cancer recurrence, ipsilateral local-regional invasive breast cancer recurrence, distant recurrence, contralateral invasive breast cancer, or any cause mortality (STEEP version 2).

Secondary Endpoints

Invasive Disease-free Survival (IDFS)
Median 4 years of follow-up (interim analysis planned)
Distant Disease-free Survival (DDFS)
Median 4 years of follow-up (interim analysis planned)
Overall Survival
Median 4 years of follow-up (interim analysis planned)
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
0.9% Normal SalinePLACEBO_COMPARATOR0.9% normal saline in subjects administered intradermally every month for first 6 months then every 6 months for next 2.5 years (11 intradermal injections over 3 years)
GLSI-100EXPERIMENTALGLSI-100 immunotherapy in subjects administered intradermally every month for first 6 months then every 6 months for next 2.5 years (11 intradermal injections over 3 years)
GLSI-100, Open-labelEXPERIMENTALOpen-label arm: GLSI-100 immunotherapy in non-HLA-A\*02 positive and HER2/neu positive subjects administered intradermally every month for first 6 months then every 6 months for next 2.5 years (11 intradermal injections over 3 years)

Interventions

NameTypeDescription
PlaceboBIOLOGICAL0.9% Normal Saline
GLSI-100BIOLOGICAL500 mcg/mL GP2 and 125 mcg/mL GM-CSF
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Eligibility Criteria

Age Range18 Years to 100 Years
SexALL
Healthy VolunteersNo
Study Sites179

Inclusion Criteria: * Histologically confirmed diagnosis of HER2/neu positive primary breast cancer for all tumors biopsied at diagnosis (multifocal, multicentric, or synchronous contralateral disease) * Completion of both neoadjuvant and adjuvant trastuzumab-based standard of care breast cancer th...

Countries:United StatesBelgiumFranceGermanyIrelandItalyPolandPortugalRomaniaSpain
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Competitive Landscape -Breast Cancer 399 trials

Top 20 of 91 competitors

CompanyTickerTrialsLead PhaseDrugs
AstraZeneca PLCAZN46PHASE3Fulvestrant, Capivasertib
Merck & Co., Inc.MRK12PHASE3Pembrolizumab, Paclitaxel, Doxorubicin, Epirubicin, Cyclophosphamide
Eli Lilly and CompanyLLY27PHASE3Abemaciclib, Standard Adjuvant Endocrine Therapy
BioNTech SE Sponsored ADRBNTX7PHASE3DB-1303/BNT323, T-DM1
Gilead Sciences, Inc.GILD13PHASE3Sacituzumab Govitecan-hziy, Eribulin, Capecitabine Product, Gemcitabine, Vinorelbine
Novartis AG Sponsored ADRNVS30PHASE3Ribociclib
Pfizer Inc.PFE34PHASE3ARV-471, Fulvestrant
BeOne Medicines Ltd. Sponsored ADRONC5PHASE3BGB-43395, Letrozole, Abemaciclib, Palbociclib, Ribociclib
Olema Pharmaceuticals, Inc.OLMA5PHASE3Palazestrant, Fulvestrant, Anastrozole, Letrozole, Exemestane
Jazz Pharmaceuticals Public Limited CompanyJAZZ3PHASE3Zanidatamab, Trastuzumab, Eribulin, Vinorelbine, Gemcitabine
Celcuity Inc.CELC3PHASE3Gedatolisib, Palbociclib, Fulvestrant, Alpelisib
Relay Therapeutics, Inc.RLAY2PHASE3Zovegalisib, Capivasertib, Fulvestrant
GSK plc Sponsored ADRGSK2PHASE3Niraparib
Greenwich LifeSciences, Inc.GLSI1PHASE3GLSI-100
Bristol-Myers Squibb CompanyBMY5PHASE2Iza-bren, Nab-paclitaxel, Paclitaxel, Capecitabine, Carboplatin
BriaCell Therapeutics CorpBCTX1PHASE3SV-BR-1-GM, Cyclophosphamide, Interferon infiltration of the inoculation site, Retifanlimab, Treatment of Physician's Choice
Incyte CorporationINCY4PHASE2Ruxolitinib, Capecitabine, Regorafenib
Natera, Inc.NTRA3PHASE2Discontinuation of the anti-HER2 maintenance therapy
Puma Biotechnology, Inc.PBYI3PHASE2Neratinib, Loperamide, Colesevelam
Atossa Therapeutics, Inc.ATOS1PHASE2endoxifen, goserelin
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Recent Changes (Last 90 Days)

MEDIUMAug 6, 2026NCT05232916Enrollment: 750 → 2250
MEDIUMAug 6, 2026NCT05232916Enrollment: 750 → 2250

Frequently asked questions about GLSI-100

What is GLSI-100 used for in breast cancer?

GLSI-100 is an investigational monoclonal antibody being developed for breast cancer. It is currently being evaluated in a Phase 3 clinical trial for HER2/neu positive breast cancer patients. The drug is administered as a peptide vaccine combined with GM-CSF to stimulate an immune response against HER2/neu expressing tumors.

What does GLSI-100 target?

GLSI-100 targets the HER2/neu protein, which is overexpressed in certain breast cancers. It is a peptide-based immunotherapy designed to elicit an immune response against HER2/neu positive tumor cells. The drug combines the GP2 peptide with GM-CSF as an adjuvant to enhance the immune system's ability to recognize and attack cancer cells.

Who makes GLSI-100?

GLSI-100 is being developed by Greenwich LifeSciences, Inc., a biopharmaceutical company traded on the Nasdaq under the ticker symbol GLSI. The company is conducting a Phase 3 clinical trial to evaluate the efficacy and safety of GLSI-100 in HER2/neu positive breast cancer patients.

What phase is GLSI-100 in?

GLSI-100 is currently in Phase 3 clinical development. It is an investigational drug and has not yet been approved by the FDA. The drug has received Fast Track designation from the FDA, which is intended to expedite the development and review process for serious conditions with unmet medical needs.

What clinical trials is GLSI-100 in?

GLSI-100 is being studied in a Phase 3 clinical trial registered as NCT05232916. This randomized, double-blind, placebo-controlled trial is recruiting approximately 2,250 participants with HER2/neu positive breast cancer. The study is being conducted in the United States and several European countries, including Belgium, France, Germany, Ireland, Italy, Poland, Portugal, Romania, and Spain.

Is GLSI-100 the same as GP2?

GLSI-100 is a combination product that includes the GP2 peptide and GM-CSF. GP2 is the HER2/neu peptide component of GLSI-100, while GM-CSF serves as an immune-stimulating adjuvant. In clinical trials, GLSI-100 is referred to as GP2 plus GM-CSF, and the study title specifically mentions GLSI-100 (GP2 + GM-CSF).