Nobody else has asked where the decay needs to fire from.
Alpha particles concentrate roughly 400 times more energy per cell diameter than the beta particles used in approved therapies like Pluvicto and Lutathera. But that energy is delivered at a range of just two to ten cell diameters. Where radioactive decay begins determines how much of that energy reaches the DNA.
That is the geometry question. Trevarx’s design thesis is that engineering the answer is what unlocks the next generation of alpha radioligand therapy.
The radiopharmaceutical category was born from a simple premise: carry radiation through the bloodstream, deliver it directly into tumors, destroy cancer cells with precision while sparing healthy tissue. FDA approvals proved the model. The entire field then raced toward the same approach: attach a radioactive payload to a targeting molecule that binds a receptor on the outside of the cancer cell. Fire from there.
Trevarx was founded on a specific observation about that approach. The cell surface is not the DNA. When alpha radiation fires from outside the nucleus, alpha particles must traverse cytoplasm and the nuclear membrane before reaching DNA, and a meaningful fraction of their energy is consumed before any DNA contact occurs. Programs that bind extracellular targets are spending their most lethal asset on distance.
AlphaPARP uses a small-molecule PARP-targeting scaffold (Parthanatine) covalently attached to the alpha emitter Astatine-211. The molecule is small enough to cross the cell membrane, small enough to enter the nucleus, and engineered to bind activated PARP1 at sites of tumor DNA damage. In that geometry, the decay event occurs adjacent to DNA, with no distance lost.
AlphaPARP is not a PARP inhibitor at therapeutic doses. It uses PARP1 as a molecular address to position alpha decay at DNA. Because the therapeutic thesis depends on DNA-proximal localization rather than BRCA/HRD synthetic lethality, AlphaPARP is designed to remain relevant where tumors retain sufficient PARP1 target expression after PARP inhibitor resistance.
| Feature | Cell-Surface Delivery (Traditional) | Trevarx Intranuclear Delivery |
|---|---|---|
| Binding Site | Cell-surface receptor or extracellular target | Nuclear PARP1 at tumor DNA damage sites |
| Primary Locus of Decay | Plasma membrane or cytoplasm | DNA-proximal, intranuclear |
| Distance to DNA | Cytoplasm + nuclear membrane; alpha range partially consumed | Designed to be near zero — at the PARP1-DNA attachment point |
| Killing Mechanism | Alpha traversal of cytoplasm and nucleus | Recoil-associated DNA break + short-range alpha released within the nucleus |
| Reported Relative Cytotoxicity | Baseline | Up to ~10× per decay event in published localization study* |
*Comparison based on public preclinical and clinical-stage disclosures and the published localization study by Lee H, JNM December 2025, doi:10.2967/jnumed.125.270175.
When AlphaPARP is bound at activated PARP1 on DNA, each Astatine-211 decay event is designed to produce two simultaneous physical effects.
Hit 1 — Short-Range Alpha Release Inside the Nucleus.
The alpha particle is released within the nucleus. With AlphaPARP positioned at PARP1 on DNA, the alpha track deposits dense ionizing energy along its path through coiled DNA, leaving a path of cell killing double-stranded DNA breaks.
Hit 2 — Recoil-Associated DNA Damage
The daughter nucleus recoils backward following decay. Because AlphaPARP is sitting on the DNA, the recoil force is transmitted directly onto the NDA backbone, causing a double stranded DNA break at the attachment site.
Together, the two mechanisms produce clustered, complex DNA damage — overlapping breaks concentrated at the same location, from two different physical mechanisms, in a single decay event.
Research published in EJNMMI Research (Babazada H et al., 2025) reports that AlphaPARP-induced DNA damage increases PARP1 expression in treated tumor cells. In an in vivo neuroblastoma model, tumor uptake of the imaging agent was elevated at day 2 compared with baseline.
The biological implication: a fractionated dosing schedule has the potential to amplify uptake and effect across successive doses, rather than diminish them. The PARP1 target can be attacked with subsequent small doses of AlphaPARP. In vivo models of repeated small dosing have resulted in exceptional efficacy.
Most alpha emitters currently in clinical development — Actinium-225, Thorium-227, Lead-212 — are large metallic elements that require bulky chelating cages to stay attached to targeting molecules. That chelation chemistry adds molecular bulk that is not designed for entry into the cell nucleus. Most constructs in development are intended for cell-surface engagement.
Astatine-211 is different. It belongs to the halogen family — chemically similar to iodine and fluorine — and behaves as a small, cell-permeable atom. It attaches to Trevarx’s proprietary PARP1-targeting scaffold through a direct covalent halide bond, keeping the entire molecule small, stable, and cell-permeable enough to be designed for intranuclear delivery.
This is a structural design choice, not a marketing preference. Programs built on heavy-metal alpha isotopes plus chelation chemistry are not directly portable to DNA-proximal delivery without rebuilding the chemistry from first principles.
PARP1 is a nuclear protein that detects single-strand DNA breaks and initiates repair. In tumors, especially tumors under treatment pressure, PARP1 activates and concentrates at sites of active DNA damage — generating a localized molecular signal that healthy tissue does not produce at comparable intensity.
AlphaPARP follows that activation signal into the nucleus and is designed to deliver alpha radiation at the DNA repair complex. The cancer’s own repair machinery becomes the delivery address.
There is a second feedback loop built into the biology. As above, AlphaPARP-induced DNA damage has been shown to increase PARP1 expression in treated tumor cells (Babazada et al., 2025). The repeated dosing schedule in the clinic is therefore a design lever, not a limitation.
PARPTrace ([¹⁸F]FTT) is Trevarx’s PET imaging agent. It is built on the same PARP-targeting scaffold as AlphaPARP but uses Fluorine-18 in a PET machine for visualization rather than Astatine-211 for therapy. PARPTrace has been evaluated in more than three hundred patients across academic clinical imaging studies at four academic institutions.
Pairing a therapeutic with a matched imaging agent for patient selection is a proven development model. PARPTrace does not establish AlphaPARP efficacy, but it supports target-informed patient selection, human biodistribution understanding, and translational development planning.
TRANSLATIONAL RISK REDUCTION
Human PARPTrace imaging informs the biodistribution and target-expression assumptions used to plan AlphaPARP development.
PATIENT SELECTION
PARPTrace is intended to support selection of patients whose tumors demonstrate sufficient PARP1 target expression.
TARGET ENGAGEMENT / MONITORING
PET imaging may support target engagement, biodistribution, and monitoring strategies during development, subject to protocol design and clinical confirmation.
Composition-of-matter patents are the strongest form of pharmaceutical patent protection because they cover the physical substance itself — not any specific use or method. Trevarx holds exclusive worldwide rights to the composition of matter for the AlphaPARP small-molecule scaffold and for the PARPTrace imaging agent.
U.S. composition-of-matter patent granted 2018. Worldwide patents granted. Exclusively licensed from Washington University in St.Louis.
U.S. composition-of-matter patent granted 2021. Worldwide patents pending. Exclusively licensed from the University of Pennsylvania.
Two Barriers to Entry. The composition-of-matter IP creates two distinct competitive barriers. The first is target selectivity: AlphaPARP is designed to bind to active PARP1 on DNA damage sites. The second is delivery geometry: the covalent halide chemistry that makes intranuclear access possible is differentiated from the chemical approach of every named alpha program currently in clinical development.
Astatine-211 was selected because its chemical properties and 7.2-hour half-life match the small-molecule PARP-targeting scaffold. It is produced in 30 MEV cyoclotrons or accelerators. Actinium-225, by contrast, depends on limited nuclear waste generator stock and depending on starter source, specialized cyclotrons, particle accelerators, or radioisotope generators — supply constraints that have affected clinical timelines for several Actinium-225 programs in late-stage development.
Current — Academic / NIH access.
Astatine-211 is currently produced at academic and federal cyclotron sites including Duke, Texas A&M, Penn, UC Davis, the University of Washington, and NIH. Access for RLT companies has been limited.
Year-end 2026 — commercial components in place.
Nusano’s 100× Astatine-211 global capacity comes online; Ionetix Astatine-211 cyclotrons online; Atley automated GMP module; ACSI lower-cost dedicated Astatine-211 cyclotrons.
By Phase 2 — nationwide capacity.
Nusano targets capable of shipping within three Astatine-211 half-lives nationwide and Ionetix and others targeting additional Astatine-211 production capacity; targeted CMO footprint expanding to five facilities nationwide; radiopharmaceutical CMO infrastructure entering the Astatine-211 market.
By Phase 3 — nationwide CMO rollout.
Anticipated FDA Astatine-211 regulatory framework in place; radiopharmaceutical platforms leveraging local compounding networks at scale.
The model mirrors the geographically distributed regional approach used for short-lived PET isotopes like Fluorine-18.
PARP1 is expressed across ovarian, prostate, breast, and pancreatic cancers and in neuroblastoma. The same AlphaPARP construct, without requiring a new targeting molecule, can be applied to each indication in sequence.
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