MART-1 Phosphopeptides Restricted by HLA-DR1 for use as Melanoma Vaccines

MAGE-A3 cancer immunotherapeutic / GSK1572932A (GlaxoSmithKline) — recombinant MAGE-A3 protein + AS15 adjuvant

The definitive cautionary precedent for single-antigen therapeutic cancer vaccines in adjuvant melanoma. DERMA was the largest melanoma vaccine trial ever run (1,345 resected MAGE-A3-positive stage III patients, 33 countries, up to 13 IM injections over 27 months) and failed both co-primary disease-free-survival endpoints; GSK terminated MAGE-A3 melanoma development. A single-epitope phospho-MART-1 vaccine targeting one melanocytic-lineage antigen sits in exactly this failed archetype and the Phase 2/3 PoS must be anchored to it, not to checkpoint-inhibitor benchmarks.

Criteria 2 and 3: same indication (adjuvant melanoma) and same modality (single-antigen therapeutic cancer vaccine); discontinued program retained ONLY as a labelled cautionary precedent that bounds Phase 2→3 PoS for any single-antigen melanoma vaccine — NOT a live anchor.

6MHP melanoma helper-peptide vaccine / 12MP + 6MHP (Slingluff / University of Virginia, NCT00118274) — investigational, academic

Closest mechanism-and-indication academic precedent: a multi-peptide melanoma vaccine that, like this asset, recruits CD4+ helper T-cell immunity in resected high-risk melanoma. Twenty-year post-hoc analysis (Nat Commun 2024) reported a durable overall-survival signal from adding 6 melanoma helper peptides vs a tetanus helper peptide (2.5-yr HR 0.65, 95% CI 0.40–1.05, P=0.08), concentrated in male patients. It establishes that CD4+-help melanoma vaccines can move OS in academic hands but only as suggestive, subgroup-limited, never-registrational data — the realistic ceiling for this asset's standalone clinical narrative.

Criteria 1 and 2: same mechanism (MHC class II / CD4+ helper-peptide melanoma vaccine) and same indication (adjuvant high-risk melanoma). Investigational academic program — used as the mechanism-true efficacy-signal anchor, not a commercial comparator.

pIRS2 / pBCAR3 phosphopeptide vaccine (Engelhard / Slingluff, UVA — NCT01846143) — first-in-human phosphopeptide melanoma vaccine, investigational

The only phosphopeptide cancer vaccine to reach humans, and from one of this patent's own co-inventors (Engelhard). The first-in-human trial used phospho-IRS2 and phospho-BCAR3 peptides — NOT this asset's phospho-MART-1 — in 15 stage IIA–IV melanoma patients. It was safe (only grade 1–2 AEs), immunogenic (T-cell responses 42% pIRS2 / 17% pBCAR3), but explicitly underpowered for efficacy. It validates that the MHC-restricted-phosphopeptide modality is clinically tractable, while showing the field advanced with different phosphoantigens, leaving phospho-MART-1 itself clinically unproven.

Criteria 1: same mechanism class (MHC-restricted phosphopeptide melanoma vaccine) from a shared inventor lineage; the mechanism-identical clinical anchor for stage costs/duration and Phase 1 PoS — investigational, not commercial.

KIMMTRAK / tebentafusp (Immunocore) — gp100 peptide-HLA × CD3 TCR bispecific

The only approved agent built on a melanoma peptide-HLA target and the relevant commercial-ceiling anchor for peptide-derived melanoma immunotherapy. It is a TCR-bispecific T-cell engager, NOT a vaccine, so it is a commercial/economic anchor only — not a mechanism match. FY2024 net product sales were $310.0M (uveal melanoma, an orphan HLA-A*02:01-restricted population). It demonstrates that even a best-in-class, approved, peptide-HLA-directed melanoma therapy in an orphan setting tops out in the low-hundreds-of-millions — a single-antigen vaccine would realistically sit well below this.

Criteria 4: nearest approved peptide-HLA-directed melanoma immunotherapy with comparable (orphan-scale) addressable economics; commercial-ceiling anchor only, explicitly NOT a same-modality match (T-cell engager, not a therapeutic vaccine).

V940 / mRNA-4157 + KEYTRUDA (Moderna / Merck — KEYNOTE-942, INTerpath-001) — individualized neoantigen mRNA vaccine

The current standard the field migrated to and the competitive reality a CMO will cite immediately. A personalized multi-neoantigen mRNA vaccine + pembrolizumab cut recurrence/death by 49% (HR 0.510) and distant-metastasis/death by 62% (HR 0.384) vs pembrolizumab alone in resected high-risk melanoma at 3 years, with FDA Breakthrough Therapy designation and a Phase 3 program. A fixed single phospho-MART-1 epitope is mechanistically outflanked by personalized many-neoantigen approaches; this comparator frames why the asset's value is as a licensable CD4+-help component rather than a standalone vaccine.

Criteria 2: same indication (adjuvant high-risk melanoma) and same therapeutic-vaccine category; investigational competitive-landscape anchor showing the modality frontier has moved to personalized multi-neoantigen mRNA.