STRC AAV + LNP Stack PK/PD
Integrated stack model answering the open question from STRC mRNA-LNP PKPD v2 OHC Tropism: does Strategy B mRNA-LNP as a maintenance layer on AAV-untransduced OHCs meaningfully lift cochlea-mean fold above therapeutic threshold, or is AAV doing all the real work?
Answer: AAV does essentially all the work. Strategy B adds <1% at realistic parameters.
Method
Four-compartment OHC partition model:
- AAV-transduced (fraction f_aav) → fold = AAV_fold_when_transduced (Iranfar 2026 / Holt 2021: 3-10x)
- LNP-tropic AAV-untransduced → fold = LNP_fold_when_tropic (v2 PKPD per-OHC: 2.5-2.85x)
- LNP-untropic AAV-untransduced → fold = 1.0 (DFNB16 baseline, OHC body survives per GeneReviews, structural connectors lost)
Cochlea-mean fold = sum(fraction × fold) across compartments. Threshold 2.0x.
Strategy B’s “added value” = stack cochlea-mean − AAV-alone cochlea-mean. “Rescue pivot” = scenario where stack passes but AAV alone fails.
Sweep: 432 parameter combinations across realistic and aspirational ranges.
Key numbers
At realistic AAV (Iranfar 60% transduction, 5× per-transduced-OHC fold) + realistic LNP (1-3% tropism, 2.85x per-tropic-OHC)
| AAV % | LNP % | AAV-alone fold | Stack fold | Strategy B lift |
|---|---|---|---|---|
| 50% | 0.8% | 3.000 | 3.007 | +0.25% |
| 50% | 3.0% | 3.000 | 3.028 | +0.92% |
| 60% | 0.8% | 3.400 | 3.406 | +0.17% |
| 60% | 3.0% | 3.400 | 3.422 | +0.65% |
| 70% | 0.8% | 3.800 | 3.804 | +0.12% |
| 70% | 3.0% | 3.800 | 3.817 | +0.44% |
Max ANY-scenario lift: 37% relative, but only at AAV 0% + aspirational LNP 20%. Not realistic.
Rescue pivots (AAV alone fails, stack passes)
7 / 432 scenarios, ALL requiring:
- AAV ≤ 20% transduction (clinically inadequate)
- LNP ≥ 10% tropism (sci-fi with current chemistry)
At Misha’s realistic AAV scenario (≥50% via Iranfar / Holt / Shu Yilai pipeline), zero rescue-pivot scenarios exist.
Worst-case AAV (20%, 3×) + various LNP
Stack maxes at 1.696 with sci-fi LNP 20% tropism — still below 2.0 threshold. Strategy B cannot save a failed AAV at realistic LNP.
Interpretation
Strategy B mRNA-LNP:
- Works per transfected OHC (max 2.85× fold, matches v2 PKPD)
- But LNP tropism 1-3% means almost all of the untransduced fraction stays at baseline
- The AAV-transduced fraction is where all the therapeutic lift comes from
- Stacking Strategy B on AAV adds measurement-noise-level contribution
The earlier “Strategy B as maintenance layer” framing was optimistic. v2 PKPD showed per-OHC therapeutic dose is achievable; stack model now shows that per-OHC achievability does not translate to cochlea-mean lift when AAV is already at 50-70% transduction.
Three scenarios where Strategy B would remain therapeutically meaningful:
- LNP tropism improves 10-20x through novel OHC-targeting lipid chemistry (A666-prestin conjugates, bacterial targeting motifs). Time horizon: 3-5 years of lipid engineering.
- AAV fails for Misha specifically (manufacturing defect, immune response during Ph1, off-target site integration). Edge case.
- AAV wears off over years and Strategy B becomes a top-up every 2-4 weeks. Possible but requires LNP tropism improvement same as (1).
Ranking delta
STRC mRNA-LNP Strategy B Full-Length (#4): Tier S → B.
Scoring:
- Mechanism 3: unchanged; the per-OHC rescue biology still works
- Delivery 2: unchanged; LNP tropism 1-3% still the binding constraint
- Misha-fit 5 → 2: was 5 because no AAV alternative; now 2 because AAV via Iranfar 2026 + Shanghai Shu Yilai is the active primary path. Strategy B is redundant for him at realistic AAV transduction.
- min(3, 2, 2) = 2 → B-tier
Status: backburner. Not killed because it remains a valid interim option if AAV fails clinically, and an academic contribution to the field. But for Misha specifically, the AAV path is the one that delivers therapeutic lift.
STRC mRNA Therapy Hypothesis (#6 Strategy A / RBM24): already A-tier “adjunctive to Strategy B; alone subtherapeutic for Misha” — stays A. Same maintenance-layer limitation applies.
STRC Mini-STRC Single-Vector Hypothesis (#3): stays S. Reinforced: the stack model formalises that AAV Mini-STRC is the primary therapeutic path for Misha. Shanghai mouse model build + Pasteur/Holt/Regeneron external validation are the active tracks that matter.
What this note does NOT do
- Does not account for cumulative AAV wear-off over 5+ years (Strategy B might meaningfully matter in year 3+ when AAV expression wanes). Model assumes steady-state.
- Does not model immune response re-dosing constraints for AAV (limits second-dose AAV, which is where Strategy B top-up logic lives).
- Assumes AAV-transduced OHCs are already at fold-saturation (doesn’t help them further with LNP). Realistically LNP might modestly boost AAV-transduced cells; ignored here for conservatism.
- Assumes independent AAV and LNP tropism. If AAV and LNP preferentially target the SAME OHCs (e.g. both via basal turn access), the stack value drops further — i.e. model is optimistic.
Connections
[part-of]index- STRC mRNA-LNP PKPD v2 OHC Tropism
- STRC Mini-STRC Single-Vector Hypothesis
[applies]2026-01-iranfar-dual-aav-strc-ctm (AAV transduction fraction reference)[applies]2021-12-holt-strc-dual-aav-science-advances (AAV fold per-OHC reference)[see-also]STRC Hypothesis Ranking[see-also]STRC LNP Cochlear Tropism Literature Scan