Greenwich LifeSciences delays 10-K amid FLAMINGO-01 data update

Greenwich LifeSciences (Nasdaq: GLSI) has disclosed that its Form 10-K for the fiscal year ending 31 December 2025 remains under audit, with completion now expected before the end of May 2026 alongside the Q1 2026 quarterly filing. The Texas-based clinical-stage biopharma said the delay stems from disagreements between auditors on final figures, principally around accounts payable linked to the global FLAMINGO-01 Phase III trial and a larger-than-expected surge in European patient screening activity during 2024 and 2025.

The company also confirmed an unaudited cash position of approximately $10.5 million as of 31 March 2026, a figure it cautioned remains subject to revision pending completion of the Q1 financial review. For a small-cap biotech running a large global Phase III, that cash balance will likely attract scrutiny from investors monitoring whether the company has sufficient runway to reach its interim analysis without additional financing.

FLAMINGO-01 open-label signals

Alongside the filing update, Greenwich LifeSciences provided a substantive readout from the open-label, non-HLA-A02 arm of FLAMINGO-01. More than 1,300 patients have been screened in total, with an annualised screen rate of approximately 800. The 250-patient non-HLA-A02 arm is now fully enrolled, giving the company roughly five times the treated-patient dataset it had at the conclusion of the Phase IIb study.

Preliminary analysis of recurrence rates following completion of the Primary Immunisation Series — a six-injection regimen administered over six months — shows an approximately 70–80% reduction in recurrence, a signal the company says tracks closely to the Phase IIb results in HLA-A*02 patients, where an 80% or greater reduction in HER2/neu 3+ overexpressor patients was observed over five years of follow-up. The company also reported a roughly fourfold increase in delayed-type hypersensitivity reactions — a surrogate immune-response marker — between baseline and month four or six, citing statistical significance (McNemar, p < 0.001). Greenwich cautioned that open-label data is preliminary and should not be read as predictive of final study outcomes.

Market context and regulatory read-across

GLSI-100 targets a relatively well-defined HER2-positive breast cancer population that has completed neoadjuvant and adjuvant trastuzumab-based treatment, a segment where recurrence prevention remains an active clinical need. The competitive landscape includes established adjuvant and extended-adjuvant therapies from larger players, but the cancer-vaccine modality — stimulating antigen-specific T-cell immunity via GP2 peptide — occupies a distinct mechanistic niche with limited direct comparators at the Phase III stage.

The FDA's Fast Track designation for GLSI-100 is meaningful in that it facilitates rolling review and more frequent agency interactions, potentially compressing the path to a Biologics Licence Application if the blinded randomised arms of FLAMINGO-01 corroborate the open-label signal. The trial is designed to detect a hazard ratio of 0.3 in invasive breast cancer-free survival with 28 events required; an interim analysis for superiority and futility will be triggered at 14 events. Given current enrolment pace, investors will be tracking when that event threshold is likely to be reached as the primary near-term catalyst.

The company's IR function is handled in part by RedChip Companies, a small-cap investor relations firm whose clients typically pay for coverage — context worth noting when evaluating the framing of the release, though the underlying clinical and financial disclosures carry independent regulatory weight as SEC-filed or associated materials.