Monoclonal antibody half-life and protection study

PRIMARY OUTCOME

Protection against SARS-CoV-2 Omicron BA.2 lung infection

EXPECTED OUTCOMES

- 1. YTE-mutant antibody demonstrates significantly extended half-life (8-12 days) compared to wild-type antibody (2-4 days) in TKI mice, with 3-4 fold higher AUC - 2. Both antibodies achieve similar peak concentrations (Cmax ~200-300 μg/mL) but YTE variant maintains therapeutic levels >10 μg/mL for >7 days vs 3 days for wild-type - 3. YTE-mutant antibody provides superior protection against Omicron BA.2 challenge with 2-3 log reduction in lung viral loads compared to controls - 4. Wild-type antibody shows minimal or no protection (≤1 log reduction) due to rapid clearance from circulation before peak viral replication - 5. Strong correlation (r>0.7) between circulating antibody levels at time of challenge and degree of viral load reduction - 6. No significant adverse effects from antibody administration with normal weight gain and clinical scores throughout study period - 7. Consistent results across male and female mice with no significant sex-based differences in pharmacokinetics or protection

SUCCESS CRITERIA

- • Half-life extension: YTE variant t1/2 >6 days vs wild-type t1/2 <4 days (p<0.001, unpaired t-test with Welch's correction) - • Protection efficacy: YTE antibody reduces lung viral loads by >2 logs compared to controls (p<0.001, one-way ANOVA with Tukey's test) - • Dose-response relationship: Significant correlation between antibody concentration and viral load reduction (r>0.5, p<0.05, Pearson correlation) - • Assay performance: ELISA CV <15% for intra-assay and <20% for inter-assay precision, qPCR efficiency 90-110% with R²>0.99 - • Data completeness: >90% of planned samples collected and analyzed successfully with no missing critical timepoints - • Statistical power: Achieved power >0.8 for primary endpoint analysis with planned sample sizes - • Reproducibility: Key findings confirmed in independent repeat experiment with similar effect sizes

PROTOCOL

**Phase 1: Antibody Preparation and Characterization** -- Days 1-7 Prepare wild-type anti-SARS-CoV-2 monoclonal antibody and half-life-extended variant (YTE mutation: M252Y/S254T/T256E in Fc region). Characterize antibodies by analytical SEC-HPLC, SDS-PAGE, and mass spectrometry to confirm purity >95% and correct molecular weights. Perform binding kinetics analysis using SPR (Biacore 8K) with SARS-CoV-2 spike protein. Measure neutralization potency against Omicron BA.2 using pseudovirus neutralization assay on HEK293T-ACE2 cells. Prepare antibodies at 2 mg/mL in sterile PBS for injection. **Phase 2: Pharmacokinetic Study Design** -- Days 8-10 Randomize 8-10 week old male and female TKI mice (n=8 per group per timepoint, total n=96) into treatment groups: vehicle control, wild-type antibody (10 mg/kg i.v.), and YTE-mutant antibody (10 mg/kg i.v.). Dose selection based on human equivalent dose calculations. Collect blood samples via submandibular bleeding at 1, 6, 24, 48, 72, 120, 168, 240, and 336 hours post-injection. Process samples immediately and store plasma at -80°C. **Phase 3: Antibody Concentration Analysis** -- Days 11-21 Quantify circulating antibody concentrations using validated sandwich ELISA specific for human IgG. Coat plates with anti-human Fc antibody (Jackson ImmunoResearch) and detect with HRP-conjugated anti-human IgG. Use purified antibodies as standards (0.1-10 μg/mL range). Calculate pharmacokinetic parameters (Cmax, t1/2, AUC, clearance) using Phoenix WinNonlin non-compartmental analysis. Statistical analysis by two-way ANOVA with Sidak's multiple comparisons test. **Phase 4: Viral Challenge Preparation** -- Days 22-24 Prepare SARS-CoV-2 Omicron BA.2 viral stock (target titer 10^6 PFU/mL) propagated in Vero-E6 cells. Verify titer by plaque assay and confirm variant identity by RT-PCR sequencing of spike gene. Prepare challenge dose of 10^4 PFU in 50 μL sterile PBS for intranasal administration. Test viral stock for mycoplasma contamination and endotoxin levels (<1 EU/mL). **Phase 5: Protection Efficacy Study** -- Days 25-35 Administer antibodies (10 mg/kg i.v.) or vehicle control 48 hours before viral challenge. Use n=12 mice per group based on power analysis for detecting 1.5-log difference in viral loads (power=0.8, α=0.05). Challenge mice intranasally with SARS-CoV-2 Omicron BA.2 under isoflurane anesthesia. Monitor mice twice daily for clinical signs using standardized scoring system. Sacrifice mice at 3 days post-challenge for peak viral replication analysis. **Phase 6: Viral Load Quantification and Analysis** -- Days 36-42 Harvest lungs aseptically and homogenize in 1 mL sterile PBS using BeadBug homogenizer. Clarify homogenates by centrifugation (10,000 x g, 10 min). Extract viral RNA using QIAamp Viral RNA Mini Kit. Perform RT-qPCR targeting SARS-CoV-2 N gene using CDC N1 primer/probe set. Quantify infectious virus by plaque assay on Vero-E6 cells with 1% agarose overlay. Calculate viral loads as log10 copies or PFU per gram lung tissue. Analyze by one-way ANOVA followed by Tukey's multiple comparisons test.

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