RIA-01 · Work Package 3 · Delivery Pairing
v0.1 · 2026-05-11
Delivery pairing: matching top WP1 candidates to Atlas Bio capsids and modalities
Maps the WP1.2 / WP2.1 top candidates to delivery vehicles. Uses the internal AAV Capsid Intelligence platform's actual scores (PHP.eB, AAV9, 4D-R100, 4D-C102) and proposes three priming-pulse-maintenance architectures by tissue.
Computational research use only — not clinical, not therapeutic, not wet-lab instruction.
★ WP3 Headline
The strongest pairing in the entire portfolio is chemical priming with Vitamin C + α-KG → AAV-OSK pulse via PHP.eB or AAV9 → chemical maintenance with Tazemetostat or a KAT8-axis tool (future), anchored on retina/CNS first.
This sequence exploits Atlas Bio's three real assets in combination: (1) the highest-conviction TET-cofactor white space from WP1.2, (2) the BBB-capable engineered capsid scores from the existing AAV platform, and (3) the FDA-approved selective EZH2-i upgrade path from WP1.2 / Tazemetostat. The KAT8 program (WP2.1) is the long-bet maintenance layer that adds the headline-novel asset once it exists.
1. The priming → pulse → maintenance architecture
Every successful partial-reprogramming program will eventually adopt some version of this three-phase structure. Each phase has a different optimal modality.
Phase 1 · Prime
Chemical priming
Oral or systemic small molecule. Days–weeks. Opens chromatin, restores demethylation cofactors, sensitizes cells.
→
Phase 2 · Pulse
OSK delivery
AAV-OSK or mRNA-OSK. Brief, transient, tissue-targeted. Drives the reprogramming wave.
→
Phase 3 · Maintain
Chemical maintenance
Cyclic small molecule, low-dose. Sustains the rejuvenated epigenetic state without driving full dedifferentiation.
Atlas Bio's competitive advantage is highest in Phase 2 (capsid intelligence platform) but the moat-quality advantage is in integrating all three phases with one scoring stack — which is what RIA-01 is built to do.
2. Atlas Bio capsid scorecard (recap from internal AAV platform)
| Capsid | BBB score | Target tissue | Pairing role in Phase 2 |
|---|
| PHP.eB | 0.71 | Brain (transcytosis-capable, mouse-validated) | CNS / neuronal OSK delivery |
| AAV9 | 0.65 | Brain, heart, muscle, liver (broad tropism) | Workhorse for systemic CNS + multi-tissue programs |
| 4D-R100 | 0.43 | Retina (engineered 4DMT capsid) | Retina / RGC OSK delivery (Sinclair Lu 2020 mechanism, engineered vehicle) |
| 4D-C102 | 0.29 | Cardiomyocytes (engineered, cardiac-specific) | Cardiac OSK delivery (lower BBB by design) |
Scores reproduced from Atlas Bio AAV Capsid Intelligence Study v3. Engineered 4DMT capsid scores from the 4DMT case study (case-studies/4dmt-capsids.html).
3. Top ranked candidate × delivery pairings
Pairing #1 — Retina / RGC rejuvenation (TOP RANKED)
Tissue: retinal ganglion cell · Anchor study: Lu et al. 2020 Nature (Sinclair) · Delivery: engineered 4D-R100 capsid
Prime
Vitamin C + α-KG
Oral, 2–4 wk priming
TET cofactor priming — restores 5hmC capacity
→
Pulse
AAV-OSK via 4D-R100
Intravitreal, single dose
Engineered retina-targeted capsid; 0.43 BBB consistent with retina-sister-tissue tropism
→
Maintain
Tazemetostat (pulsed)
Low-dose, cyclic
Selective EZH2-i; FDA-approved drug; off-label-trialable
EVIDENCE FOUNDATION
Lu et al. 2020 demonstrated AAV-OSK in RGCs restores vision in mouse glaucoma and aged-vision models. The 4D-R100 capsid is an engineered, clinical-stage retinal vehicle. Vitamin C / α-KG TET cofactor priming has independent evidence (Esteban 2010, Carey 2015). Tazemetostat has FDA approval and a defined safety database.
HYPOTHESIS
The combination has not been tested. The mechanistic case — (1) priming opens demethylation capacity, (2) OSK pulse drives the reprogramming wave, (3) selective EZH2-i sustains H3K27me3 release without DZNep's off-target liabilities — is internally consistent. The retina-first choice keeps the in-scope tissue clean and uses the strongest published proof-of-concept.
SAFETY
Intravitreal delivery is the safest route for an experimental gene-therapy + small-molecule combination because of tissue-compartment isolation. Tazemetostat's secondary malignancy boxed warning applies systemically; cyclic / low-dose strategy required. Vitamin C / α-KG safety is excellent. Co-administration with NAD+ supplements would partially antagonize the maintenance layer (per WP1.3 finding) — needs to be in the trial-design memo.
Pairing #2 — CNS / neuronal rejuvenation
Tissue: cortical and hippocampal neurons · Anchor: BBB-capable engineered capsids · Delivery: PHP.eB or AAV9
Prime
Vitamin C + α-KG
Oral, BBB-permeable, 4–6 wk
→
Pulse
AAV-OSK via PHP.eB
IV systemic; PHP.eB BBB 0.71
AAV9 (0.65) as the human-translatable alternative since PHP.eB is mouse-optimized
→
Maintain
Tazemetostat or RepSox
Cyclic, pulsed
HYPOTHESIS
CNS is the natural extension of the retina-first beachhead because the chemistry transfers (vitamin C is BBB-permeable; α-KG less so but pro-drug strategies exist) and PHP.eB / AAV9 are the highest-BBB capsids in the platform. The translation question is whether PHP.eB efficacy transfers to humans — AAV9 is the conservative human-trial vehicle.
SAFETY
Systemic AAV exposure raises pre-existing-immunity considerations (anti-AAV9 neutralizing antibody prevalence 30–60% adult population depending on geography). Tazemetostat's systemic exposure adds the secondary-malignancy concern. CNS-restricted dosing via intrathecal route is the safer-path option but reduces translational simplicity.
Pairing #3 — CNS rejuvenation with KAT8 maintenance (FUTURE / long bet)
Tissue: CNS / retina · Anchor: WP2.1 KAT8 program output · Status: dependent on KAT8 tool compound existence
→
Pulse
AAV-OSK via PHP.eB / 4D-R100
→
Maintain
KAT8 activator (TBD)
NSL/MSL complex stabilizer (WP2.1 Strategy 1)
Or selective SIRT6-i (WP2.1 Strategy 2)
HYPOTHESIS
The Pairing #3 architecture is the same as Pairing #2, except the maintenance layer is replaced with a KAT8-axis intervention. This restores H4K16ac directly — the aging mark most consistently lost. If the WP2.1 KAT8 program produces a tool compound (Strategy 1 lowest-risk path), this pairing becomes the headline novel asset combination.
SAFETY
Conditional on the KAT8 program output. Chronic systemic KAT8 hyperactivation is high-risk (essentiality concerns); tissue-targeted, pulsed delivery is the mitigating architecture. Atlas Bio's capsid platform is the architectural fit.
4. Delivery decision tree
START: choose tissue
|
+-- Retina / RGC?
| |-- Use 4D-R100 (engineered retinal capsid)
| |-- Route: intravitreal (compartmentalized, safest)
| |-- BBB consideration: N/A (eye is privileged compartment)
| +-- VERDICT: Pairing #1 (top ranked)
|
+-- CNS / brain?
| |-- Use PHP.eB (mouse) or AAV9 (human-translatable)
| |-- Route: IV systemic or intrathecal
| |-- BBB consideration: PHP.eB 0.71 > AAV9 0.65; AAV9 wins on clinical translatability
| +-- VERDICT: Pairing #2 (CNS extension)
|
+-- Cardiac?
| |-- Use 4D-C102 (engineered cardiac capsid)
| |-- Route: IV systemic with cardiac tropism
| |-- BBB consideration: low BBB (0.29) is correct - keep out of brain
| +-- VERDICT: Future case study (not WP3 v0.1 scope; tissue-specific WP3.2)
|
+-- Liver / muscle / other?
| |-- Use AAV9 (broad tropism)
| |-- Tissue-specific 4DMT or other engineered capsids if available
| +-- VERDICT: Future case studies (WP3.2+)
|
+-- Choose chemistry layers:
|
+-- Prime: Vitamin C + alpha-KG (TET cofactor)
| - Highest WP1 composite score, lowest competitive density, best safety
| - Replaces or augments any vitamin-C-permissive existing supplement
|
+-- Pulse: AAV-OSK (cassette: O, S, K - drop MYC for safety)
| - Cyclic dosing if re-dosing is feasible for the capsid
| - Or mRNA-OSK if compartment allows (Turn Bio paradigm)
|
+-- Maintain (near-term): Tazemetostat low-dose cyclic
| - FDA-approved selective EZH2-i
| - Drops in directly as a DZNep upgrade
|
+-- Maintain (future): KAT8 activator (when WP2.1 produces one)
- Replaces or augments Tazemetostat
- H4K16ac axis - the headline novelty
5. Modality comparison for the OSK pulse layer
| Modality | Cargo limit | Tissue control | Re-dose tolerance |
Atlas Bio advantage | Primary use case |
| AAV-OSK (PHP.eB / AAV9) |
~4.7 kb (tight for OSK) |
Capsid tropism + tissue-specific promoter |
Limited (NAb response) |
HIGHEST — capsid intelligence platform |
CNS, RGC, tissues where one-shot durable expression is acceptable |
| AAV-OSK (engineered 4D-R100 / 4D-C102) |
~4.7 kb |
Tissue-restricted by design |
Limited but possibly improved by surface-modified engineered capsids |
HIGH — 4DMT case study integrated |
Retina (R100), cardiac (C102), other tissue-targeted programs |
| mRNA-OSK(MLN) LNP |
Larger cargo OK |
LNP biodistribution-dependent (liver-dominant systemic; local for skin/joint) |
Re-dosable |
MEDIUM — LNP scoring not Atlas core |
Skin, immune cells, ex vivo cell rejuvenation, indications where re-dosing is essential |
| Episomal / DNA-only |
Variable |
Tissue-dependent on delivery |
Variable |
LOW — not Atlas focus |
Research tool; possibly ex vivo |
6. Integrated study recommendation: Retina-first beachhead program
RIA-01's recommendation for Atlas Bio's first concrete reprogramming program based on WP1 + WP2.1 + WP3 synthesis:
| Element | Choice | Rationale |
|---|
| Indication |
Age-related vision degeneration (RGC-restricted first; glaucoma adjacency) |
Cleanest published proof-of-concept (Lu 2020); compartment-isolated route; small organ; fast readouts; FDA precedent for gene therapy in eye (Luxturna) |
| Tissue |
Retinal ganglion cells |
RGC-specific OSK rejuvenation already published; 4D-R100 capsid available |
| Capsid |
4D-R100 primary; AAV2-based ITR options for regulatory familiarity |
Engineered for retina; Atlas Bio platform-scored; 4DMT clinical-stage |
| OSK cassette |
Doxycycline-inducible OSK (no MYC) |
Cyclic / pulsed control is the safety architecture; drop MYC for oncogenic risk reduction |
| Priming chemistry |
Oral Vitamin C + α-KG (4–6 wk pre-pulse) |
WP1.2 highest composite; excellent safety; supports TET-mediated demethylation |
| Maintenance chemistry (near-term) |
Tazemetostat cyclic low-dose |
FDA-approved selective EZH2-i; mechanism-clean alternative to DZNep |
| Maintenance chemistry (future) |
KAT8 activator (WP2.1 program output) when available |
Highest white-space; H4K16ac axis restoration; replaces Tazemetostat in the architecture |
| Aging-clock readouts |
Retinal Horvath clock, RGC transcriptomic age, OCT visual-function endpoints |
WP5 (rejuvenation-marker matrix) will detail; visual function is the FDA-translatable endpoint |
| Competitive moat |
4D-R100 + engineered capsid intelligence + RIA-01 integrated scoring |
Iduna is the most direct delivery competitor (per WP1.4); chemical priming + maintenance layer is not in their disclosed plan |
| Co-administration warning |
Avoid NAD+ precursor supplementation during maintenance phase |
WP1.3 conflict: SIRT6 activation antagonizes H4K16ac axis; relevant for any future KAT8 maintenance |
7. Limitations and next-pass questions
- WP3 v0.1 covers retina + CNS only. Cardiac (4D-C102), liver, muscle, and skin tissue-pairing analyses are deferred to WP3.2 / WP3.3.
- Modality scoring assumes Atlas Bio's existing AAV platform is the primary asset. mRNA-LNP scoring is genuinely thinner because it's not the platform's strength — partnership with an LNP-capable company (Turn Bio adjacency, others) is the natural path if mRNA matters for a future indication.
- Re-dosability is a major open question for AAV in cyclic partial reprogramming. Cyclic OSK is the safety architecture in the Belmonte / Browder literature; AAV's one-shot biology constrains this. Engineered capsids designed for re-administration (low-NAb-cross-reactivity variants) are a separate Atlas Bio research thread.
- The retina-first beachhead recommendation is unchanged from WP3.1 to the final WP synthesis — this is intentional and reflects the convergence of evidence across the WP1/2/3 work.
Next passes
- WP4: Safety risk matrix — per-candidate, per-tissue, per-architecture safety profile (consolidates WP1/2/3 safety lanes).
- WP5: Aging-clock endpoint suite — concrete biomarker pairing for the retina-first program.
- WP-final: Synthesis — ranked opportunity list, white paper draft, future wet-lab memo.