FDA clears first commercial GP2 vial lot for Phase III FLAMINGO-01 trial

The U.S. Food and Drug Administration has approved the use of Greenwich LifeSciences’ first commercially manufactured lot of GP2 vials in the Phase III FLAMINGO-01 trial of GLSI-100, the company announced. The clearance marks a milestone in the development and manufacturing pathway for an investigational immunotherapy intended to prevent breast cancer recurrence.

GLSI-100 combines GP2, a nine–amino–acid peptide derived from the HER2/neu protein, with granulocyte-macrophage colony-stimulating factor. The regimen is administered intradermally after mixing the peptide and GM-CSF at the time of dosing, a method designed to stimulate GP2-peptide specific immunity. The product remains experimental; its safety and efficacy are being evaluated through the ongoing FLAMINGO-01 Phase III study.

Greenwich said its commercial manufacturing program began with production of three active pharmaceutical ingredient lots in 2023 at an approved commercial facility. Those API lots, the company states, could yield roughly 200,000 doses of GP2. In 2024 the company filled its first finished commercial vial lot at a commercial facility and has initiated stability programs across the four commercial lots, the three API lots plus the first finished-vial lot. Greenwich reports three years of stability data supporting the expiration dating for the approved vial lot.

The FDA review encompassed data from those commercial lots, and the agency cleared the first finished-vial lot for use in U.S. sites participating in FLAMINGO-01. Greenwich plans to begin shipping the approved vials to all 40 U.S. clinical sites “in the coming weeks,” and expects to manufacture at least two additional finished lots to build the manufacturing database it says will be necessary for a U.S. Biologics License Application. GLSI-100 holds Fast Track designation in the U.S., and the company intends to include commercial manufacturing data from multiple lots in a planned BLA submission under that pathway.

With the FDA clearance, Greenwich’s leadership frames the step as reducing regulatory and manufacturing risk. “With our manufacturing investments in 2023 and 2024, and now the FDA's review and approval to use the first commercial lot of finished GP2 vials in FLAMINGO-01, we have taken major steps to further de-risk the filing of a BLA in the US. We plan to start using these new GP2 vials in the coming weeks at all 40 US sites. We have 3 years of stability data to support the GP2 vial expiration date which may translate to the commercial expiration date of GP2 vials,” CEO Snehal Patel said.

The move carries implications beyond the company’s balance sheet. Approving a commercial lot for clinical use can streamline supply to trial sites and strengthen the evidence package manufacturers must present to regulators. For patients at risk of recurrence, faster, reliable supply through commercial manufacturing could shorten timelines to potential market access if GLSI-100 proves effective. Yet meaningful questions remain about transparency and equity: the identity and oversight of the contract manufacturers, the assays and release criteria used for lot release, and whether shipping and site transitions will be simultaneous or staggered, factors that can affect enrollment, retention and access for diverse patient populations.

Regulatory clarity on outstanding manufacturing data will shape the program’s path to licensure and commercial availability. Greenwich lists investor and media contacts for follow-up: Snehal Patel, Investor Relations, Office (832) 819-3232, Email info@greenwichlifesciences.com; and Dave Gentry, RedChip Companies Inc., Office 1-800-RED CHIP (1-800-733-2447), Email dave@redchip.com. The company issued a press release via GlobeNewswire from Stafford, Texas.