Glioblastoma (GBM) is the most common and most aggressive primary brain tumor in adults, with historical median progression-free survival of 4.0-6.9 months and median overall survival of 14.6-17.0 months on standard-of-care chemoradiation. The blood-brain barrier (BBB) historically excluded most peptide therapeutics from CNS oncology — most peptides are too large or too polar to cross the tight-junction endothelium that protects brain parenchyma.
2026 brought the first credible Phase 2 evidence that peptide-mechanism oncology can work in GBM. Sapience Therapeutics' lucicebtide (ST101) — a first-in-class peptide antagonist of CCAAT/enhancer-binding protein β (C/EBPβ) — crossed the BBB with confirmed tumor uptake and target engagement, and the Window-of-Opportunity Phase 2 study (n=9 evaluable, April 27 cutoff) projected a median progression-free survival of 28.4 months in newly diagnosed GBM plus standard chemoradiation. The Monday June 1 ASCO 2026 poster session in Chicago delivers the full data.
Stories here cover GBM peptide programs across BBB-penetrant peptides, C/EBPβ and other transcription-factor targets, and the broader CNS oncology peptide-therapeutic landscape. See #sapience-therapeutics, #lucicebtide, and #asco-2026 for adjacent threads.
At ASCO 2026, Sapience Therapeutics presented updated Phase 2 data for lucicebtide (ST101), a first-in-class peptide antagonist of the transcription factor C/EBPβ, now studied in 125 patients. In newly diagnosed glioblastoma plus standard of care, projected median PFS reached 28.4 months and median OS was not yet reached, with 6 of 9 patients alive beyond 22.3 months. Spatial transcriptomics confirmed on-target activity through negative enrichment of the C/EBPβ regulon and suppression of mesenchymal transformation, with no dose-limiting toxicities or related serious adverse events.
Dana-Farber Cancer Institute researchers led by David Reardon (Director, Center for Neuro-Oncology) and Catherine Wu (Chief, Division of Stem Cell Transplantation and Cell Therapies) presented Phase 1 data at ASCO 2026 on NeoVax — a personalized neoantigen peptide vaccine — combined with pembrolizumab in newly diagnosed glioblastoma. The study excluded dexamethasone (an immune suppressant) and added pembrolizumab to enhance anti-tumor activity. Vaccine-stimulated anti-tumor activity was still evident in some patients after one year, with vaccine-specific T cells migrating into the brain and tumors following vaccination. The MGMT-methylated patient subgroup showed median survival meaningfully exceeding historical observations, though the authors emphasized this requires cautious interpretation given the lack of a randomized comparator arm. The timing of pembrolizumab administration didn't affect immune-response stimulation, but pembrolizumab-before-NeoVax-priming may extend overall survival. NeoVax adds to the personalized neoantigen vaccine cohort (BioNTech autogene cevumeran, Moderna intismeran autogene, Evaxion EVX-01) anchoring the broader peptide cancer vaccine field.
Sapience Therapeutics' May 21 ASCO 2026 data update on lucicebtide (ST101) — a first-in-class C/EBPβ peptide antagonist — included a specific data point worth surfacing for the Tuesday cycle. In the Phase 2 Window-of-Opportunity study (n=9 evaluable as of April 27 data cutoff), patients with newly diagnosed glioblastoma (ndGBM) treated with lucicebtide plus standard-of-care chemoradiation achieved a projected median progression-free survival of 28.4 months — meaningfully exceeding the 4.0-6.9 month historic benchmark range. Six of nine patients remain alive past 22.3 months against a historical median OS range of 14.6-17.0 months. Median overall survival has not yet been reached. Lucicebtide crossed the blood-brain barrier with confirmed tumor uptake and target engagement via negative enrichment of the C/EBPβ regulon in tumor and myeloid cells. The poster session is scheduled for Monday June 1.
Sapience Therapeutics announced May 22 positive Phase 2 clinical and pharmacodynamic data update from its lucicebtide (ST101) trial in glioblastoma ahead of the ASCO 2026 Annual Meeting (May 29-June 2 Chicago). The Phase 2 Window-of-Opportunity study evaluates lucicebtide alone and in combination with standard-of-care chemoradiation, with dosing both before and after surgical resection. Nine patients were evaluable for analysis; the maturing data show durable progression-free and overall-survival improvements with a well-tolerated safety profile. Lucicebtide is a first-in-class peptide antagonist of CCAAT/enhancer-binding protein β (C/EBPβ) — a transcription factor that drives tumor aggressiveness, immune evasion, and stemness in glioblastoma. The 125-patient program across recurrent GBM monotherapy and newly diagnosed combination cohorts is the largest peptide-mechanism dataset in GBM to date. The Monday June 1 poster session details the efficacy, pharmacodynamics, and safety in newly-diagnosed patients.
Recent reviews and real-world observation studies aggregate the state of peptide-vaccine immunotherapy for glioblastoma. A 2024 Nature Communications real-world observational study reported clinically meaningful outcomes for personalized peptide vaccines; the UCPVax + temozolomide trial (NCT04280848) showed 97% anti-TERT immune response, 48% epitope spread, median OS 17.9 months, and 26% alive at 2 years. The peptide-vaccine modality is one of multiple approaches (mRNA, dendritic cell, neoantigen) advancing alongside immune checkpoint blockade.