Accelerated Blood Clearance of PEGylated CRISPR LNPs

Redosing Scenario

Anti-PEG antibody titer 8 AU

PEG surface stealth coating 92%

Kupffer cell phagocytic activity 100%

Simulation time scale 1.0×

Blood Compartment

Circulating LNP (% of dose)100.0%

Elimination half-life—

Delivered to hepatocytes0.0%

Elapsed time0.0 min

Circulating LNP (intact)

Opsonized → Kupffer capture

Delivered → hepatocyte

How it works

A first dose of PEGylated lipid nanoparticle (LNP) is normally "stealthed" against the reticuloendothelial system. But PEG itself is weakly immunogenic: it primes B-cells that secrete anti-PEG IgM (peaking ~5–7 days later). If a second LNP dose arrives while that titer is high, the antibodies opsonize the particles, fix complement, and Kupffer macrophages in the liver sinusoids clear them within minutes — the "Accelerated Blood Clearance" (ABC) phenomenon. This is the main reason repeat-dose CRISPR/mRNA-LNP therapies must manage redosing intervals or use PEG-alternative coatings.

k_clear(Ab) = k_base·(1 − stealth) + k_immune·Kupffer·Ab^2 / (Ab^2 + Kd^2)
k_total     = k_clear + k_target                 (competing first-order removal)
C_blood(t)  = C0 · e^(−k_total·t)                 (intact, still-circulating dose)
Delivered(t)= C0 · [k_target / k_total] · (1 − e^(−k_total·t))
t½          = ln(2) / k_total

Anti-PEG antibody titer — pre-existing immunity from a prior LNP/mRNA-LNP exposure; drives complement-mediated opsonization via a Hill-type dose-response (Kd = 40 AU).
PEG stealth coating — reduces baseline non-immune reticuloendothelial uptake, but cannot fully protect once specific antibodies are bound.
Kupffer activity — liver macrophage phagocytic state; scales the immune-mediated clearance term.
Prime dose resets Ab titer to 0 (naive patient). Re-dose now keeps the current titer but restarts the blood-concentration clock at t = 0 — try priming, then raising the titer slider to ~60–80 AU before re-dosing to see delivered payload collapse.

Two competing first-order pathways remove LNPs from blood: immune/RES clearance (k_clear) and productive uptake by target hepatocytes (k_target, held constant here). Their ratio sets what fraction of the injected dose ever reaches its therapeutic target — exactly the algebra behind real LNP redosing studies.

Liver sinusoid loop — LNPs recirculate through Kupffer and hepatocyte zones

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