Serum Virus-Neutralizing Antibody Titers in Clinical Trial Participants With and Without Immunocompromise Receiving Pemivibart, a Long-Acting Monoclonal Antibody for COVID-19.

In 30 seconds

This analysis of phase 3 CANOPY and phase 1 trial data examined measured and calculated serum virus-neutralizing antibody titers after pemivibart in participants with and without significant immunocompromise. In CANOPY, predose measured titers against XBB.1.5 were low, while pemivibart increased day-28 geometric mean titers against this variant by >55-fold, with similar levels in both cohorts. Across the trials, calculated titers correlated with measured titers (all Spearman correlation coefficients ≥0.73, P < .0001). The findings indicate limited cross-protection from prior immune experience with earlier variants and support calculated titers as a predictor of neutralization potential.

Key findings

• Predose measured titers against XBB.1.5 were low across CANOPY cohorts (range, 78.6-119.8).
• Pemivibart increased day-28 measured geometric mean titers against XBB.1.5 by >55-fold, with similar levels in participants with and without immunocompromise.
• Calculated and measured titers were significantly correlated across trials (all Spearman correlation coefficients ≥0.73, P < .0001).
• Measured titers were substantially higher against earlier Delta and BA.4/5 variants than against XBB.1.5.

Why it matters

Neutralization against circulating SARS-CoV-2 variants may differ substantially from responses to earlier variants, so prior immune experience does not necessarily imply strong cross-protection. The observed rise in titers after pemivibart and the correlation between calculated and measured titers provide evidence relevant to interpreting immunobridging assessments, while antibody titers alone do not establish clinical protection.

What to keep in mind

The reported outcomes are neutralizing antibody titers; the abstract does not report clinical efficacy outcomes.